US20060232382A1 - Intelligent station using multiple RF antennae and inventory control system and method incorporating same - Google Patents

Abstract

An inventory control system and method that tracks inventories of items with RFID tags, includes a reader unit and an intelligent station that tracks RFID tags to determine item information of items to be inventoried. The reader unit transmits and receives RF signals. The intelligent station includes a first RF antenna connected to the reader unit by a first transmission cable through a first switch, and one or more additional RF antennae connected to the reader unit by the same first transmission cable through additional switches. An inventory control processing unit receives item information from the intelligent stations to update inventory information regarding the items to be inventoried.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• This application claims the benefit of priority under 35 U.S.C. § 119(e) of provisional application Ser. Nos. 60/346,388, filed Jan. 9, 2002, and 60/350,023, filed on Jan. 23, 2002, the disclosures which are incorporated herein in their entireties.
FIELD OF THE INVENTION
• The present invention relates generally to the field of using multiple RF (radio frequency) antennae in an intelligent station to track items tagged with RFID (radio frequency identification) tags. More generally, the present invention is directed to an inventory control method and system that uses the intelligent station to track and inventory items that are tagged with RFID tags.
BACKGROUND OF THE INVENTION
• Radio frequency identification (RFID) systems typically use one or more reader antennae to send radio frequency (RF) signals to items tagged with RFID tags. The use of such RFID tags to identify an item or person is well known in the art. In response to the RF signals from a reader antenna, the RFID tags, when excited, produce a disturbance in the magnetic field (or electric field) that is detected by the reader antenna. Typically, such tags are passive tags that are excited or resonate in response to the RF signal from a reader antenna when the tags are within the detection range of the reader antenna. One example of such a RFID system including details of suitable RF antennae is described in U.S. Pat. No. 6,094,173, the contents of which are incorporated herein in their entirety. In order to improve the detection range and expand “coverage” it is known to use coplanar antennae that are out of phase. One example of such an antenna is provided in U.S. Pat. No. 6,166,706.
• The detection range of the RFID systems is typically limited by signal strength to short ranges, for example, frequently less than about one foot for 13.56 MHz systems. Therefore, portable reader units are moved past a group of tagged items in order to detect all the tagged items since the tagged items are typically stored in a space significantly greater than the detection range of a stationary or fixed single reader antenna. Alternately, a large reader antenna with sufficient power and range to detect a larger number of tagged items may be used. However, such an antenna may be unwieldy and may increase the range of the radiated power beyond allowable limits. Furthermore, these reader antennae are often located in stores or other locations were space is at a premium and it is expensive and inconvenient to use such large reader antennae. In another possible solution, multiple small antennae may be used but this configuration may be awkward to set up keeping in mind that space is often at a premium.
• However, use of multiple antennae (or components) has the drawback that multiple transmission cables are used to connect a reader unit to the multiple antennae and/or that the multiple antennae cannot be individually controlled when they are all connected by a single transmission cable to the reader unit.
• By way of background,FIG. 1 is a block diagram that illustrates the basics of a prior art RFID system. Areader unit100 may typically be connected through RS-232 or similar digital communication to aterminal102 such as a computer terminal. Thereader unit100 is connected by acable203 to areader antenna200. Thereader antenna200 typically consists of at least aloop201 and atuning circuit202. Although thetuning circuit202 is shown as a localized part inFIG. 1, one skilled in the art would recognize that it might be distributed around theloop201. Thereader antenna200 in turn communicates by lowpower radio waves105 with one ormore RFID tags106 that are typically associated with items, objects (animate or inanimate) or persons that are to be tracked by the RFID system.
• Thetransmission cable203 is typically characterized by its impedance, which in a simplified form, is approximately the square root of inductance L divided by capacitance C of the transmission cable. For coaxial cables, the impedance is commonly 50 or 75 ohms.
• Generally, thetransmission cable203,antenna loop201, andtuning circuit202 are connected together in a manner that most efficiently utilizes the RF power at a desired frequency, which for a given RFID system using a loop antenna, such asantenna200, is typically a “high” frequency such as 13.56 MHz. Another common “low” frequency that is often used for RFID systems is 125 kHz. “Ultrahigh” (UHF) frequencies such as 900 MHz or 2.45 GHz within the RF range are also used with different antenna designs.
• A system using multiple antennae powered by a single reader unit and using a multiplexer switch to alternate between the antennae has also been-known. Such a system is conceptually represented inFIG. 2 where twoseparate antennae200aand200bare connected to a reader andmultiplexer unit101 throughrespective transmission cables203aand203b. The use of multiple antennae typically improves the spatial coverage when reading tags, without requiring more than one reader unit. The main disadvantage of the arrangement disclosed inFIG. 2 is the need for a separate transmission cable to each of the antennae. Since space is often at a premium, the use of these separate cables is a disadvantage because additional space is needed to install or position each of these separate cables. This disadvantage is accentuated when more than two antennae are used with one reader unit since all of these multiple antennae require separate transmission cables.
SUMMARY OF THE INVENTION
• In one aspect, the present invention provides an intelligent station that tracks RFID tags, the intelligent station including: a reader unit that transmits and receives RF signals; a first RF antenna connected to the reader unit by a first transmission cable through a first switch; and one or more additional RF antennae connected to the reader unit by the same first transmission cable through one or more additional switches. The term “intelligent,” as used herein, means that the system can, through transmission of radio frequency signals, capture, store, and lookup data, and monitor unique identifiers associated with trackable items.
• In a further aspect, each of the first and one or more additional RF antennae includes a loop and a tuning circuit.
• In another aspect of the present invention, the reader unit includes a tuning circuit for the first and one or more additional RF antennae, with the tuning circuit connected to the first and one or more additional RF antennae through the first transmission cable.
• In another aspect, the present invention includes: a reader unit that generates and receives RF signals; and a control unit that is operatively connected to the reader unit and to first and one or more additional switches, wherein the control unit is configured to selectively operate the first and one or more additional switches to connect the reader to the first and one or more additional RF antennae, respectively. The reader unit and the control unit may be separate devices or combined in a single unit.
• In yet another aspect of the present invention, the intelligent station further includes a second transmission cable that connects the reader unit to auxiliary RF antenna loops, each of the auxiliary RF antenna loops arranged proximate to a corresponding one of the first and one or more additional RF antennae. The auxiliary antennae receive an unmodulated RF signal that powers up the tags, which are normally not powered in the absence of an RF signal. As used herein, “unmodulated RF signal” is an RF signal without superimposed data. A “modulated RF signal” is an RF signal carrying superimposed data.
• In a further aspect, the reader unit includes a second tuning circuit, proximate to the reader unit, that is connected to the auxiliary RF antenna loops through the second transmission cable. The second tuning circuit is configured to tune the auxiliary RF antenna loops.
• In yet another aspect, the present invention provides a second transmission cable that connects the reader unit to the first and one or more additional RF antennae through the first and one or more additional switches, respectively. The reader unit transmits an unmodulated RF signal to the first and one or more additional RF antennae through the second transmission cable, and transmits a modulated RF signal to the first and one or more additional antennae through the first transmission cable.
• In a further aspect of the present invention, the first switch is configured to operate in only three states: a first state such that the first switch only transmits the modulated RF signal to the first RF antenna; a second state such that the first switch only transmits the unmodulated RF signal to the first RF antenna; and a third state such that both the modulated RF signal and the unmodulated RF signal bypass the first RF antenna. The second switch includes a multi-pole switch configured to operate in only three states: a first state such that the second switch only transmits the modulated RF signal to the associated second RF antenna; a second state such that the second switch only transmits the unmodulated RF signal to the second associated RF antenna; and a third state such that both the modulated RF signal and the unmodulated RF signal bypass the associated second RF antenna. Each of the switches can be controlled independently of each other, thus, for example, the first and second switches may be set to transmit modulated and unmodulated signals, respectively, at the same time. In addition, a two-pole switch may be used which is configured to operate in one of two states (one state being to pass modulated RF signals to the associated antenna, and the other state being to pass no signals to the associated antenna).
• In a further aspect, the present invention provides: additional RF antennae connected to the reader unit through the same first transmission cable; and additional switches arranged between the first transmission cable and the additional RF antennae, respectively.
• In one aspect, an RF transmission cable has a single branch serving all antennae, that is antennae are connected to a reader unit through a RF transmission cable in a series arrangement.
• In another aspect, an RF transmission cable has two or more branches, each serving one or more antennae, That is, antennae are connected to the reader unit through the RF transmission cable in a parallel-series arrangement, with each branch on the RF transmission cable selectable by use of a switch.
• In another aspect, intelligent stations contain RF signal processing electronics to perform some of the signal processing otherwise done by the reader.
• In yet another aspect, each of the one or more additional switches include a PIN type diode.
• In another aspect, the present invention provides an intelligent inventory control system that uses RFID tags to determine item information of items to be inventoried, the intelligent inventory control system including one or more intelligent stations. Each intelligent station comprises a first RF antenna connected to the reader unit by a first transmission cable through a first switch; and one or more additional RF antennae connected to the reader unit by the same first transmission cable through respective one or more additional switches. The reader unit may be located apart from or within one of the intelligent stations. The inventory control system further includes an inventory control processing unit, connected to a data store, that receives item information from the intelligent station to update inventory information regarding the items to be inventoried.
• In yet another aspect, the present invention provides a method of inventory control for items tagged with RFID tags, the method including: providing a plurality of intelligent stations, each intelligent station including a reader unit that transmits and receives RF signals, a first RF antenna connected to the reader unit by a first transmission cable through a first switch; and a one or more additional RF antennae connected to the reader unit by the same first transmission cable through respective one or more additional switches; determining item information of items to be inventoried by selectively energizing the first and one or more additional RF antennae of each of the intelligent stations to determine item information of items that are located on the respective intelligent stations; and processing the determined item information to update inventory information of the items to be inventoried.
• In one aspect, each station has its own reader unit. However, one reader unit may also serve many stations.
• In a further aspect of the present invention, the inventory control method includes selectively controlling the first and one or more additional switches to energize the first and one or more additional RF antennae and detect item information from items with RFID tags that are within range of the respective energized one or more additional RF antennae.
• In a further aspect of the present invention, the inventory control method includes software control of the RF power level generated by the reader unit. In a preferred embodiment, testing would determine how much RF power the reader unit must provide to achieve optimal results for each connected antenna, which are positioned at different distances along the RF cable. This information would be stored, for example, in a look-up table or other equivalent indexed data storing means. Thereafter during operation, the power level for each antenna would be set based on this predetermined level stored in the look-up table, so that antennae at differing distances along the RF transmission cable may all operate at essentially equal power.
• In an alternate embodiment, the power provided to each antenna could also depend on additional factors, for example, on the type of antenna. Therefore, in the alternate embodiment, both the distance and type of the antenna could be used to determine and store the optimal power level for a particular antenna.
• In a further aspect of the present invention, the inventory control method includes RF amplifier devices, such as RF filter amplifiers, located periodically along the RF transmission cable such as in every N^thshelf to boost the RF signal strength.
• In a further aspect of the present invention, the inventory control method includes updating the determined item information of items in a data store.
• In a further aspect, the present invention provides that the inventory control method includes, for each intelligent station, providing a second transmission cable to connect the reader unit to one or more auxiliary antenna loops arranged proximate to respective ones of the first and one or more additional RF antennae, wherein the reader unit transmits a modulated RF signal through the first transmission cable and transmits an unmodulated RF signal through the second transmission cable.
• In yet another aspect, the inventory control method according to the present invention includes providing, for each intelligent station, a second transmission cable that connects the reader unit to the first and one or more additional RF antennae through first and one or more additional switches, respectively, wherein the reader unit transmits an unmodulated RF signal to the first and one or more additional RF antennae through the second transmission cable, and transmits a modulated RF signal to the first and one or more additional RF antennae through the first transmission cable.
• In another aspect the inventory control method of the present invention provides, for each intelligent station, configuring the first and one or more additional switches to operate in one of only three states: a first state that only transmits a modulated RF signal to a respective one of the first and one or more additional RF antennae; a second state that only transmits an unmodulated RF signal to the respective one of the first and one or more additional RF antennae; and a third state such that both the modulated RF signal and the unmodulated RF signal bypass the respective one of the first and one or more additional RF antennae.
BRIEF DESCRIPTION OF THE DRAWINGS
• The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate without limitation presently preferred embodiments of the invention, and, together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.
• FIG. 1 is a block diagram illustrating the basics of a prior art RFID system.
• FIG. 2 is a block diagram illustrating a prior art RFID system with multiple antennae connected to a reader unit.
• FIG. 3A is a block diagram illustrating an embodiment of an inventory control system that uses intelligent stations in accordance with the present invention.
• FIG. 3B is a block diagram illustrating another embodiment of an inventory control system that uses intelligent shelves in accordance with the present invention.
• FIGS. 3C and 3D are flowcharts illustrating processing performed by the control unit of the inventory control system according to the present invention.
• FIG. 3E is a block diagram illustrating another embodiment of an inventory control system that uses intelligent stations in a parallel-series configuration.
• FIG. 3F is a block diagram illustrating another embodiment of an inventory control system that uses intelligent stations in another parallel-series configuration.
• FIG. 3G is a block diagram illustrating a tee switch for use in a parallel-series configuration.
• FIG. 3H is a block diagram illustrating an inline switch for use in a parallel-series configuration.
• FIG. 3I is a block diagram illustrating an exemplary method of carrying RF and digital communications on one cable.
• FIG. 3J is a block diagram illustrating a method of using switches to minimize undesirable effects of an RF cable extending past a selected antenna.
• FIG. 4A is a block diagram illustrating one embodiment of the present invention showing an RFID system with multiple antennae connected to a reader unit.
• FIG. 4B is a schematic diagram showing a logical switch.
• FIGS. 5 and 6 are block diagrams showing alternate embodiments of the present invention having multiple antennae.
• FIG. 7 is a block diagram illustrating another embodiment of the present invention in which two separate transmission cables transmit modulated and unmodulated RF signals to multiple antennae each having several loops.
• FIG. 8 is a block diagram illustrating an alternate embodiment in which the modulated and unmodulated RF systems use the same antenna loops.
• FIG. 9A is a schematic diagram of an exemplary switch that may be used with the embodiment disclosed inFIG. 8.
• FIG. 9B is a schematic diagram of another exemplary switch that may be used with the embodiment disclosed inFIG. 8.
• FIG. 10A is a circuit diagram of a switch using a PIN diode that may be used with various embodiments of the present invention.
• FIG. 10B is a circuit diagram showing how an antenna may be “detuned.”
• FIG. 10C is a circuit diagram showing another way that an antenna may be “detuned.”
• FIG. 10D is a circuit diagram showing yet another way that an antenna may be “detuned.”
• FIG. 11A is a diagram illustrating various layouts of reader antennae on shelves.
• FIG. 11B is a diagram illustrating the use of tags within shelves.
• FIG. 12 is a diagram illustrating one method of making a wire antenna.
• FIG. 12A-C are diagrams illustrating alternate ways of securing the ends of wires on a substrate.
• FIG. 13 is a diagram illustrating an alternate method of making a wire antenna.
• FIG. 13A is a diagram illustrating various alternate wire antenna shapes.
• FIG. 14 illustrates another method of making a wire antenna.
• FIG. 15 is a diagram that illustrates a device and method of applying foil tape ribbons to a web or planar substrate to form a foil antenna.
• FIG. 16 is a diagram illustrating another method of depositing conductive pathways on a substrate to form a foil antenna.
• FIG. 17 is a diagram illustrating a cross section of anapplicator2200 for depositing conductive pathways.
• FIG. 18 is diagram that illustrates a method to lay down a simple rectangular conductive pathway using the apparatus shown inFIG. 15.
• FIGS.18A-B illustrate foil strips folded over.
• FIG. 19 shows an embodiment where aconductive trace2300 being laid down overlaps a previous conductive trace.
• FIG. 20 is a laminated structure containing a foil strip antenna.
• FIG. 21 is a diagram illustrating the use of a milling machine to form openings in a substrate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Unless otherwise specified, “a” or “an” means one or more. The present invention provides an intelligent inventory control system including one or more intelligent stations that can detect RFID tags using multiple antennae. The RFID tags are attached to items to be detected or tracked. In certain preferred embodiments discussed herein, the intelligent station system is designated as an intelligent “shelf” system since the intelligent station system provided by the present invention is suitable for tracking items on shelves of stores and warehouses for inventory control or other tracking purposes. However, it is to be understood that the present invention is not limited to intelligent shelf systems since one skilled in the art would recognize its applicability to other uses such as, for example, tracking items in closed receptacles, other storage volumes, and particular spaces. Examples of such closed receptacles or storage volumes include, without limitation, rooms, closets, cabinets, cupboards, refrigerators, freezers, pegboards, clothing racks, trailers, warehouses, pallets, counters, and other similar enclosures, spaces, or racks. It may be used in doors, doorways and other portals, in floors or floor mats, or in ceilings. It is also to be understood that the intelligent stations may be used in orientations other than the horizontal orientation typically associated with a shelf. For example, the intelligent shelves may be used in a vertical orientation as, for example, on the wall of a container, or the back or side area or surface of a storage volume.
• For use in clothing racks, various embodiments are envisioned including linear or circular racks. For circular racks in particular, it is envisioned that two antennas may be used that are orthogonally disposed in two vertical planes within the center of the circular rack. The antenna may be driven by a single reader but the length of their lead-in cables differs, preferably, by ¼ of the RF wavelength, or alternately, a two-way 90 degree power splitter is used (e.g. MiniCircuits PSCQ-2-13) to put the two antennas 90 degrees out of phase. As a consequence the magnetic field orientation set up by the two antennas “rotates” once each cycle of the RF wave, so that all RFID tags around the circular rack may be read.
• For use with clothing racks, another embodiment provides, on the clothing rack, one or more antenna loops, for example positioned or hanging at one or both ends of the rack, or distributed as hangers amidst the clothing. If the antenna loops are provided in the form of hangers, these may be fabricated by running conductive wire through narrow (e.g. ¼″-⅜″ diameter) thermoplastic tubing, then heat-forming the tubing to create hanger-shaped antennas. The same method could be used to create self-supporting antennas in any shape.
• A planar antenna can be limited in its ability to read tags that are oriented parallel to the magnetic field lines created by the antenna. The read range may be extended and tag orientation limitations overcome by providing for an RF-powered antenna (antenna connected to a reader) and one or more passively coupled antennae that are not connected directly to the reader. These passively connected antennae are excited or powered through inductive coupling with the powered antenna. The passively coupled antenna will have a magnetic field, preferably, 180 degrees out of phase with the actively coupled antenna. Thus the orientation of the resulting magnetic field will oscillate, so that RFID tags in otherwise unfavorable orientations may still be read. In one embodiment, the passively coupled antennas could be provided in the shelf itself, for example, with actively powered antennas in the front of the shelf and passively coupled antennas in the back of the shelf, with all antennas being in the plane of the shelf. Other embodiments include having passively coupled antennae in the vertical plane at the ends of shelves or backs of shelves. Other embodiments include using at least one actively powered antenna within an enclosure such as a box, cabinet, or passageway, with one or more passively coupled antennae to provide better reading range or better flexibility in reading tags that are disposed in any orientation. Other embodiments include having passively coupled antennae in the vertical plane at the ends of shelves or backs of shelves. Other embodiments include for a given shelf having passively coupled antennae in the horizontal plane some distance above the shelf, preferably just under the next shelf up.
• In a preferred embodiment, the multiple antennae may be put on a self-supporting shelf or may be embedded into a thin mat that can be laid on existing store shelves.
• For example, as shown in the block diagram ofFIG. 3A,independent shelf systems501a,501b. . .501nand502a,502b. . .502nare each provided withmultiple antennae200 that are each connected to areader unit120 by atransmission cable222. Eachreader unit120 has a controller orcontrol unit124 that uses acontrol cable221 in selecting which antenna is active at any time. Between shelves, thecables221 and222 may be interconnected usingconnectors526. While the embodiment disclosed inFIG. 3A shows that each group of shelves has an RFID system with areader unit120 connected tomultiple antennae200, one skilled in the art would recognize that a single reader unit may be configured to connect to multiple antennae on more than one shelf that are located proximate to each other, or each shelf may be configured to have its own reader unit.
• The block diagram ofFIG. 3B shows an alternate embodiment where eachshelf503a,503b. . .503nis provided withmultiple antennae200. Themultiple antennae200 are each connected to areader unit120 by atransmission cable222. Eachreader unit120 has acontroller124 to select which antenna is active at any time. Thiscontroller124 may be a microprocessor. Furthermore, the shelves may havesecondary controllers125 that co-operate with thecontroller124 to select antennae. Thesecondary controllers125 may be microprocessors with sufficient outputs to control all the antennae within the associated shelf, as well as controllingoutput devices510, such as shelf-edge displays, for displaying information such as pricing. Theoutput devices510 could display information using visible and audible signals as would be recognized by those skilled in the art. Usingsecondary controllers125 may reduce the number of wires required inconnectors526 between shelves.
• Thecontrol unit124 may selectively operate any or all the switches by sending commands through a digitaldata communication cable221, for example by sending a unique address associated with each switch, as with would be possible, for example, by using a Dallas Semiconductor DS2405 “1-Wire®” addressable switch. Each such addressable switch provides a single output that may be used for switching a single antenna. Preferably thecontrol unit124 may selectively operate any or all the switches by utilizing one or moresecondary control units125. For example, thesecondary control unit125 may be a microprocessor such as a Microchip Technology Incorporated PICmicro® Microcontroller, which can provide multiple outputs for switching more than one antenna, such as all the antennas in proximity to thesecondary control unit125. Thecontrol unit124 may also be a microprocessor such as a MicroChip Technology Incorporated PICmicro® Microcontroller. Communications between thecontrol unit124 and thesecondary control unit125 can be implemented by using digital communication signals in accordance with well known communication protocols such as RS-232, RS-485 serial protocols, or Ethernet protocols or Token Ring networking protocols. Such communications through thesecondary control unit125 may, in addition to selecting the desired antennae, also include commands to operate additional features. Examples of such features include providing displays (for example, light LED's) proximate to the antennae, displaying alphanumeric text through appropriate visual displays, or outputting audible information in the proximity of the antennae.
• In a preferred embodiment, the intelligent shelf system is controlled through the electronic network. A controlling system that controls the intelligent shelf system will send command data to thecontrol unit124 via RS-232 or similar protocol. These commands include but are not limited to instructions for operatingreader unit120, instructions for operating the antennae switches, and auxiliary information to be displayed by shelves for example with lights, visual displays, or sound. Thecontrol unit124 is programmed to interpret these commands. If a command is intended for thereader unit120, thecontrol unit124 passes that command to thereader unit120. Other commands could be for selecting antennae or displaying information, and these commands will be processed if necessary bycontrol unit124 to determine what data should be passed through digitaldata communication cable221 to thesecondary control units125. Likewise thesecondary control units125 can pass data back to thecontroller124, as can thereader unit120. Thecontroller124 then relays result data back to the controlling system through the electronic network. The inventorycontrol processing unit550, shown inFIGS. 3A and 3B, is one example of such a controlling system. As discussed further herein with respect to the intelligent shelf system, the electronic network and controlling system are used interchangeably to depict that the intelligent shelf system may be controlled by the controlling system connected to the intelligent shelf system through an electronic network.
• At a minimum,control unit124 must decide whether a command from the electronic network should be sent toreader120, or should be send on thedigital communication cable221. Also,control unit124 must relay data it receives from thedigital communication cable221, and fromreader unit120, back to the electronic network. In the minimum configuration for example, the electronic network would for example issue a command to read a single antenna. Thecontrol unit124 would a) set the proper switch for that antenna, b) activate the reader, c) receive data back from the reader, d) deactivate the reader, and e) send the data back to the electronic network.
• FIG. 3C is a flowchart illustrating exemplary processing of a command signal from a host by thecontrol unit124. Instep330, thecontrol unit124 determines whether there is a command for the control unit124 (it may do so by interrogating a memory location periodically). Thecontrol unit124 then determines instep332 whether the command was for thereader120 and, if so, sends the command to thereader unit120 instep334. If not, instep336, thecontrol unit124 decodes the command and sends appropriate instructions to thesecondary controller125. Thereafter, instep338, thecontrol unit124 determines whether a response has been received from thereader unit120 if a command had been sent to the reader instep334. If a response has been received, then instep340, thecontrol unit124 passes the response back to the host. Thereafter, instep342, thecontrol unit124 determines whether a response has been received from thesecondary control unit125 in response to the instruction sent instep336. If a response has been received from thesecondary control unit125 instep342, the response is interpreted by thecontrol unit124 and sent to the host in step344. Thereafter, the processing control returns to step330 in which thecontrol unit124 determines whether there is another command from the host that needs to be processed.
• Thecontrol unit124 may also perform some management functions otherwise handled by the electronic network. For example, the electronic network might issue a command to find a certain article on the entire shelf system associated withcontrol unit124. In such a case, the control unit would manage a series of tasks such as a) determine how many antennae were in its system, b) set the proper switch for the first antenna, c) activate the reader, d) receive data back from the reader and save it, e) deactivate the reader, f) set the proper switch for the next antenna until all the antennae have been activated, g) activate the reader until all the antennae have been read. In the preferred embodiment, when all antennae had been read, thecontrol unit124 or the electronic network (“host” or the “controlling system”) would analyze its accumulated data and report back only the location(s) of the desired item.
• FIG. 3D is a flowchart illustrating exemplary management function processing performed by control unit according to the present invention. In step350, thecontrol unit124 receives a command from a host application that requests a count of the total number of antennae controlled by thecontrol unit124. Therefore, instep352, thecontrol unit124 determines the number of antennae controlled directly by thecontrol unit124. Thereafter, instep354, thecontrol unit124 issues a command to thesecondary control units125 to select the next antenna on their list and waits for a confirmation from thesecondary control units125 instep356. Insteps358 and360, a “read” command is sent to thereader120 that awaits and reads the data from the selected antenna and sends the data to the host application instep362. Thereafter, the control unit sends a “standby” command to thereader120 instep364 and determines instep366 whether all the antennae have been read. If it is determined that all the antennae have been read instep366, the processing is terminated. Otherwise, the process control returns to step354 so that thecontrol unit124 can issue a command to the secondary control units to select the next antenna on the list that has not yet been selected.
• An additional advantage of placing thecontrol unit124 between the electronic network and the reader units is that different types ofreaders120 can be used as desired. The commands from the electronic network to the control unit may be generic and not reader-specific. For example the electronic network can send to the control unit a “read antennas” command. The control unit in turn can translate this command into the appropriate command syntax required by each reader unit. Likewise the control unit can receive the response syntax from the reader unit (which may differ based on the type of the reader unit), and parse it into a generic response back to the electronic network. The command and response syntax may differ for each type ofreader unit120, but thecontrol unit124 makes this transparent to the electronic network.
• The block diagram ofFIG. 3E shows an alternate embodiment where thecontroller124 andreader120 are contained inshelf504a. As would be recognized by those skilled in the art, it is also possible for the controller and reader to be apart from any shelf. Adigital communication cable221 connects thecontroller124 tosecondary controllers125, andRF transmission cable222 connects thereader120 to theantennae200. Thecontroller124 may operate abranch switch527 that selects which of the groups of shelves (for example504b-504n, or505b-505n) will be selected. InFIG. 3E, thebranch switch527 is used with a “parallel-series” connection method for thesecondary controllers125 and the antennae connected to thesecondary controller125. That is, instead of acontroller124 andreader120 operating all of the shelves in single series arrangement, the RF and digital communication lines are branched (that is, each of the branches are parallel to each other) before continuing on throughshelves504b-504nin series, and505b-505nin series. The parallel-series configuration inFIG. 3E may be advantageous for an aisle of shelves where typically there are approximately four levels of shelves (each of which may be connected in parallel), with each level having perhaps 10-20 shelf units connected in series. In certain situations a parallel-series configuration may also be desired from an RF transmission standpoint. For example, if an aisle has 4 levels of shelves each with 12 shelf units each having four antennae, the parallel-series configuration connects in parallel four groups of 48 antennae, while the series-only configuration would have to connect in series one group of 192 antennae. The RF transmission cable for the series-only configuration might thus become too long for efficient operation.
• The block diagram ofFIG. 3F shows an alternate embodiment where thecontroller124 andreader120 are arranged apart from any shelf.Digital communication cable221 connectscontroller124 to thesecondary controllers125, andRF transmission cable222 connects thereader120 to theantennae200. Thecontroller124 orsecondary controller125 may operate atee switch528 that selects which of the shelves or groups of shelves (for example506a, or507a-507b) will be selected. Thetee switch528 may be separate from or part of a shelf as would be recognized by one skilled in the art. InFIG. 3F, thetee switch528 is used with another “parallel-series” connection arrangement. That is, instead of acontroller124 andreader120 operating all shelves in series, the RF and digital communication lines are branched off (that is, connected with a multi-drop or “tee” arrangement with each of the branches arranged in parallel) to shelves or groups of shelves that are arranged in series. This configuration allows the RF signal to be switched by thetee switch528 into a shelf or group of shelves, or to bypass the shelf or group of shelves. The tee or multi-drop configuration shown inFIG. 3F may be used to reduce the number of switching elements through which the RF transmission cable passes.
• InFIG. 3F theportion221aof the control cable that extends beyondshelf506a, and theportion222aof the RF cable extends beyondshelf506a, are outside of the shelf. However, as would be recognized by those skilled in the art, these extended portions of the cables may also be contained within the shelf. Additional extendedcontrol cable portions221band additional extendedRF cable portions222bmay be used to connect to more shelves or groups of shelves. Likewise, additional shelves (not shown) may be added to groups of shelves, for example to shelves506a-506bas would be apparent to those skilled in the art.
• FIG. 3G shows anexample tee switch528 on anexample shelf507a. The tee switch contains a switch, forexample PIN diode207c. Asecondary controller125 associated withshelf507amay activatePIN diode207cto allow the RF signal fromRF cable222aintoshelf507a, where it may be routed throughswitches214 toantennae200. The RF energy also may continue alongRF cable222bto optional additional tee switches, and finally to aterminator215. Thus typically there may be two parallel loads on theRF cable222a—the activated antenna and theterminator215. Acircuit217, for example, an isolator circuit that is well known to those skilled in the art, may be used to match the impedance toreader120.
• FIG. 3H shows an exampleinline switch529 that may be used on anexemplary shelf507a. The inline switch contains a switch, for example, aPIN diode207d. Asecondary controller125 associated withshelf507amay activatepin diode207dto allow the RF signal from theRF cable222ato continue alongRF cable222b, or deactivatePIN diode207dto prevent the RF signal from continuing alongRF cable222b. Preferably,tee switch528 and inline switch229 may be used together to either route the RF signal to theshelf507aor toRF cable222b. With the use of one or more inline switches such asinline switch529,isolator circuit217 may not be necessary. However, theinline switch529 may result in some RF energy loss.
• FIG. 3I shows an exemplary method of combining the RF and digital communication on a single cable. Theprimary controller124 sends adigital command250 intended for the intelligent stations. Aconverter251 converts the digital data to a superimposeddigital signal252 that may be superimposed on the RF cable. For example, this superimposed digital signal may be at a different frequency than used byRFID reader120. This superimposed digital signal may pass through afilter253, such as theexemplary inductor253 shown inFIG. 3I. It then is superimposed onto the RF cable. Anotherfilter254 may be used to block the superimposed signal from reaching theRFID reader120.
• The combined RF and digital signals pass downcable222ato one or moreintelligent stations261,262,263, etc. (only261 and262 shown inFIG. 31). Upon reaching exemplaryintelligent station261, the combined signal may pass through anotherfilter255, such as an inductor sized to block the RF signals from the RFID reader. The superimposed digital communication passes throughfilter255 and into areceiver circuit256 that retrieves the digital information and passes it tosecondary controller125, and optionally to additionalsecondary controllers260.
• Thesecondary controller125 may send information back to theprimary controller124 through atransmitter circuit257, for example operating at a frequency other than the RF frequency ofreader120, and optionally at a different frequency than used for communicating from the primary controller (or control unit)124 to the secondary controller (or control unit)125. Such information may be received byreceiver circuitry258, converted to appropriatedigital signals259 and returned to theprimary controller124.
• A variation on the method for digital communication between theprimary controller124 andsecondary controller125 is to send digital communications from theprimary controller124 as a series of pulses at two or more DC voltages. Preferably, both voltages are high enough to power any circuitry associated with thesecondary controller125,peripherals510, etc that require DC power. These voltages may be sent fromdigital transmitter circuit251, and received byreceiver circuitry256, which could be a simple voltage comparator circuit. Communication from thesecondary controller125 back to the primary controller may be provided by having the digital transmitcircuitry257 provide two different levels of current draw or load on the communications cable, for example by switching in and out a transistor feeding a resistor. Such variations in the current draw would then be sensed by thereceiver circuit258 and converted into digital data for theprimary controller124.
• FIG. 3J illustrates an exemplary method using switches to minimize the undesirable effects of an RF cable extending past a selected antenna. It will be understood from the preceding descriptions that switches may be controlled by the intelligent station system through use of secondary controllers (or control unit).FIG. 3J shows areader unit370 connected to a series of antennas371-377. The series of antennae are also denoted as 1^st, 2^nd, Nth, etc. Each antenna has associated with itcircuitry380. The circuitry may include acoaxial cable381 carrying the RF signal. An RF-carrying center conductor may be shorted to the coaxial shield byshunt switch382, or connected to tuning circuitry and thereafter theantenna371 through aselect switch383. The coaxial shield is electrically continuous as denoted byline384. The coaxial shield would typically be grounded. The coaxial center conductor is likewise continuous.
• The distance between successive antennae is, preferably, an integer submultiple of a quarter-wavelength of the RF signal. For example, an RF signal at 13.56 MHz travelling through standard coaxial cable with polyethylene dielectric has a quarter wavelength of approximately 12 feet. Thus, as shown inFIG. 3J, a one-foot coaxial length between antennae could be used to provide a one-twelve submultiple of a quarter wavelength spacing. Other integer submultiples are possible, for example a 1.5-foot coaxial length between antennae could be used to provide a one-eighth submultiple.
• To illustrate the method, theNth antenna373 could be selected by closingselect switch385 to direct the RF signal toantenna373. Also,shunt switch386 is closed to short the RF signal to the coaxial shield atantenna375, which is located a quarter wavelength further along the RF cable. A short circuit at one-quarter wavelength distance along the RF cable is seen as an infinite impedance, and minimizes the adverse effects of the RF cable extension past the selected antenna. At the end of the series of antennae, there may optionally be additional shunting switches as denoted by378 and379.
• In the preferred embodiments, the intelligent station system is modular, using inexpensive components to handle data from the multiple antennae. Multiple antennae within a shelf may be activated in sequence or, optionally, with phase delays to enhance their effectiveness as is within the abilities of those skilled in the art.
• With reference to the figures,FIG. 4A is a block diagram illustrating one embodiment of the present invention that shows an RFID system withmultiple antennae200,210 (only two shown for convenience) connected to areader unit120. Therefore, the RFID system disclosed herein could be used to implement the intelligent stations501a-nor502a-nshown inFIG. 3A.FIG. 4A is not intended to limit the present invention since those skilled in the art would recognize various modifications, alternatives, and variations thereof. Furthermore, one skilled in the art would recognize that the present invention, and its construction and method of operation would apply to transmissions and detection at other frequencies also as long as power and regulatory requirements are satisfied. The RFID system may comprise a single shelf or the multiple antennae may be arranged on proximate shelves and connected to a single reader unit using connectors, for e.g., co-axial or other connection means. As shown inFIG. 4A, a singleRF transmission cable222 is used to connect to both theantennae200 and210. Thetransmission cable222 terminates in aconventional terminator215. Thereader unit120 is associated with acontrol unit124 but does not have a multiplexer. Instead thecontroller124 is designed to controlswitches204 and214 located at theantennae200 and210, respectively. Thecontrol unit124 may also communicate withsecondary control units125, for example, located proximate to the antennae. Thesecondary control unit125 may include microprocessors or addressable devices that may cooperate withcontrol unit124 in selecting the antennae.
• In one embodiment, theswitches204 and214 are connected to thecontrol unit124 by aseparate cable221. Those skilled in the art would recognize that other means, including wireless means, or different frequency signals superimposed on the RF signal carried on thecable222, may be used to connect thecontrol unit124 to theswitches204 and214. Theswitches204,214 are controlled so that at any time, only one of theantennae200,210 is connected to thereader unit120 through thecable222.
• FIG. 4B is a schematic diagram showing alogical switch204 that toggles between an open (dotted line) and a closed position, which powers the antenna. Such a logical switch may be used with the embodiment discussed with respect toFIG. 4A.
• FIG. 5 is another embodiment of the present invention that is similar to the embodiment discussed above with respect to FIG.4A, except that theantennae200 are all identical, as shown inFIG. 5. Therefore, the tuningcircuits202 may all be identical, which simplifies antenna fabrication. Therefore, thereader unit120 is connected bytransmission cable222 andswitches204 and214 to respective multipleidentical antennae200.
• FIG. 6 is block diagram of an alternate embodiment that shows a benefit when themultiple antennae200 are identical. Portions of thetuning circuitry202 may be moved back to acommon tuning circuit213 at or proximate thereader unit120 itself. Therefore, thereader unit120 is connected to themultiple antennae200 through acommon tuning circuit213 that is provided at thereader unit120. As would be recognized by those skilled in the art, amain tuning circuit202 or212 may still be provided for eachantenna200.
• FIG. 7 is a block diagram illustrating another embodiment of the present invention in which twoseparate transmission cables222 and230 transmit modulated and unmodulated RF signals, respectively, to multiple antenna configurations each of which includeantenna loops201 and231. Associated with thereader unit130 is acontrol unit134. Thereader unit130 is designed so that a RF signal can be split to allow an unmodulated RF signal to be transmitted through aseparate cable230 and through atuning circuit232 intoantenna loops231 that are associated with theRF antennae201. Each of theRF antennae201 is associated withrespective antenna loops231. As before, thereader unit130 also generates a modulated RF signal that is transmitted through thetuning circuit212 and thetransmission cable222 to themultiple antennae201.Respective switches204 and214 connect therespective antennae201 to thetransmission cable222 and also connect therespective antenna loops231 to thetransmission cable230.
• In one embodiment, the unmodulated RF system, including thetuning circuit232, thecable230, and theantenna loops231 may all be powered continuously. In contrast, the readerantenna data loops201 may only be turned on one at a time by suitably controlling theswitches204 and214. Because theloops231 can be powered continuously, there is no start-up time required for RFID tags to charge up during data transfer. Such a system could advantageously be used in situations where the RFID tags need to be frequently read. Furthermore, this embodiment also allows handheld reader units to read the tags at any time because the tags are always powered in view of the continuous powering of the unmodulated RF system. Theunmodulated cable230 has aterminator216 at the end of thecable230. In this context, it should be understood that the term “continuous” power may include a percentage duty cycle if required by legal or other limits. Alternatively, the unmodulated RF system can be activated just prior to activating the modulated RF system for each antenna.
• FIG. 8 is another embodiment that is similar to the embodiment discussed above with respect toFIG. 7. In this embodiment, the modulated RF signal throughcable222 and the unmodulated RF signal throughcable230 are routed through thesame antennae201. Theswitches204 and214 are preferably configured so that the modulatedRF signal222, orunmodulated RF signal230, or neither signal, is routed into a givenantenna201. That is, theswitches204 and214 are designed so that they can only operate in three states: (I) a first state in which only the modulated RF signal is transmitted to anantenna201; (II) a second state in which only the unmodulated RF signal is transmitted to theantenna201; and (III) a third state in which both the modulated RF signal and the unmodulated RF signal bypass theantenna201.
• Such a switching operation can be implemented with groups of single or multi-pole RF switches. In operation, this embodiment allows for anantenna201 to be inactive until just before its turn to be polled. At that point, the unmodulated RF signal can be switched into theantenna201 through thetuning circuit232, thetransmission cable230 and theappropriate switch204,214 to “warm up” the nearby RFID tags. Thereafter, the modulated RF signal is switched into thatantenna201 through thetuning circuit212, thecable222, and theappropriate switch204,214 to efficiently acquire data from the RFID tags that have just been warmed up.
• FIG. 9A is a simplified schematic diagram of aswitch205 that may be used, for example, with the embodiment discussed with respect toFIG. 8.FIG. 9A is not intended to limit the present invention since those skilled in the art would recognize various modifications, variations, and alternatives thereon. Whenswitch205A is thrown to the left to connect one pole ofantenna loop201 onto the center conductor of modulated RF signalcoaxial cable222, with the other pole connected to the shield of the same cable, the modulated RF signal is transmitted to theantenna201. Ifswitch205A is thrown to the right, the signal in the modulatedcable222 continues on to another antenna.Switch205B is shown thrown to the right, so that the unmodulated RF signal continues on toward another antenna. Ifswitch205B is thrown to the left, the unmodulated RF signal will be passed through theantenna201. If both switches A and B are thrown to the right, both signals will bypass the antenna which will be completely inactive.Switch205 is designed so thatswitches205A and205B cannot both be thrown to the left.
• FIG. 9B is a simplified schematic diagram of analternative switch205C that may be used, for example, with the embodiment discussed with respect toFIG. 8. This diagram shows that the common (or ground) wire may not need to be switched, and that a switch may be branched off of the RF cable instead of being directly inline with the cable. Whenswitch205C is thrown to the left, it connects one pole ofantenna loop201 onto the center conductor of modulated RF signalcoaxial cable222, with the other pole connected to the shield of the same cable, so the modulated RF signal is transmitted to theantenna201. Ifswitch205C is thrown to the center, the unmodulated RF signal230 will be passed through theantenna201. Ifswitch205C is thrown to the right, neither RF signal will enter the antenna which will be completely inactive. Note in the case ofswitch205C that the RF signals also continue down their respective cables, past theantenna201, regardless of theswitch205C setting.
• FIG. 10A shows a circuit diagram for a RF switch that may be used, for example, asswitch204 or214 discussed earlier herein with respect to various embodiments of the present invention.FIG. 10A is not intended to limit the present invention since those skilled in the art would recognize various modifications, variations, and alternatives thereof. As shown, the RF switch utilizes a PIN (P-type, I-type, N-type) diode207 (for example, Microsemi part number 900-6228) which acts in a similar way to a regular PN diode except that it is able to block a RF signal when the switch contact is open. When the switch contact is closed, thePIN diode207 becomes forward biased and conducts the RF signal. The control signal used to select the antenna may also be superimposed (not shown) on the RF signal that is used to read the RFID tags. Such a control signal could be separated from the RF signal by a band pass filter and then go on to an addressable switch, which selectively activates the RF switch utilizing a PIN diode. InFIG. 10A, the control signal is provided on separate wiring instead of using the RF signal cable. While superimposing the control signal on the RF signal cable may require fewer conductors and/or connectors between antennae or between intelligent stations, it requires additional electronic components to separate the signals at each antenna. Thus it may be more efficient to have separate wiring for the control signal.
• FIG. 10B illustrates a circuit diagram for detuning an antenna so that, if the antenna is not selected for activation, it will not resonate when a nearby antenna is selected. If the antenna is not selected, then thePIN diode207ashorts out tuning capacitor211a, and thereby changes the frequency of the antenna so that it will not be active at the frequency used to operate the antenna to read the RFID tags.
• Using a PIN diode such as207ato short out tuning capacitors and detune an antenna means thatPIN diode207amay be run under power for significant lengths of time. This may generate heat and waste power. Therefore the system may be designed to only detune antennae that are immediately adjacent to the antenna currently being read. Which antennae are adjacent may be determined by several methods. For example, this may be specified during design, or found by observation after assembly, or may be determined with the RFID reader during operation as described further herein.
• FIG. 10C shows another circuit diagram where aPIN diode207bis used to tune the loop. Here the loop is in tune whenPIN diode207bis energized. Therefore, thePIN diode207bis not required to remain on while the loop is not being read. This may save power and reduce heat generation.
• While the examples here include use of PIN diodes for the switching and detuning functions, other electronic components such as, for example, FET (field effect transistor) or MESFET (metal-semiconductor FET) devices may also be used as would be recognized by those skilled in the art.
• FIG. 10D shows another circuit diagram where a switch, for example field effect transistor (FET)208, within the resonant part of the circuit is used to detune the loop. Here the loop is in tune whenFET208 is deenergized, and detuned whenFET208 is energized. In the energized state, theFET208 draws little power. Furthermore, in this position within the circuit, when theFET208 is energized it sufficiently detunes the loop antenna so that RF tends not to enter the tuning circuit. Therefore it may not be necessary to provide a separate FET or PIN diode to select the loop.
• FIG. 10B illustrates one aspect of the present invention that variable capacitors (for example, variable capacitors211a-cshown inFIG. 10B) may be used to tune the antenna, that is, to cause it to resonate at the same frequency as the RF signal from a reader unit. As the surroundings of the antenna may influence the tuning, any structure enclosing the tuning circuit is preferably designed to keep the adjustable components accessible from the outside, for example, by locating them at an edge of the structure (such as a shelf edge) or by providing access holes for tuning devices (such as servo-controlled screwdrivers).
• Furthermore, since tuning an antenna can be a trial and error process and time-consuming, it is desirable to permit the tuning to be done automatically. According to one aspect of the present invention, this is accomplished by providing an automatic tuning unit (not shown) that would temporarily attach computer-controlled servo-driven screwdrivers to adjustment screws associated with the adjustable capacitors. To achieve optimal tuning, the automatic tuning unit (which may include a computer or other suitably programmed microprocessor) would receive feedback from a conductive connection to the antenna being tuned, or from an RFID reader that would detect which tags were identified from an array of tags in a predetermined or known spatial (preferably two or three-dimensional) arrangement. The tuning unit, based on a set of rules, experimentally developed or developed from experience, would manipulate the adjustment screws to achieve optimal tuning. Alternatively, the controller or secondary controller may adjust the tuning of each antenna by electronic adjustment, for example by remotely setting adjustable voltage-controlled capacitors within the tuning circuit. This method would minimize the need for using mechanical or servo controlled adjustments for tuning. Voltage-controlled capacitors in the tuning circuit could also be used to detune antennae so they would not resonate when they were not selected for reading.
• In one embodiment, RFID tags may be placed within the shelf itself, preferably one or more situated within the read range of each individual antenna. These RFID tags provide for each antenna a known response when that antenna is read during a self-test mode. Thus, whether or not the shelf supported any RFID-tagged items, there would always be at least one self-test RFID tag that should be found in range of the antenna. If such RFID tags were not found, thecontrol unit124 orsecondary control unit125 may institute a self-tuning process. If after self tuning the self-test RFID tags could still not be read, then a message could be sent to the electronic network indicating the need for shelf maintenance. Instead of placing the self-test RFID tags within the shelf, they could also be placed elsewhere in range of the antennae, for example on the rear or side wall of a shelf.
• FIG. 11A is diagram illustrating alternate antenna loop configurations within a single shelf unit.Shelf300 contains asingle antenna loop301.Shelf310 containsantenna loops311 and312. With more than one loop within a shelf, there arise multiple operating modes. For example,loop311 could be active, orloop312 could be active, or both loops could be active or inactive at the same time. The present invention contemplates that both loops could be active simultaneously with a phase difference in their input RF signal. Such as phase difference can be introduced by various electronic means well known to those skilled in the art. For example, a phase difference can be introduced by using a different length coaxial cable to feed one antenna loop as compared with the other.
• As seen inFIG. 11A,shelf320 contains four antenna loops321-324. This is shown as an example, since there may be more or less than four antenna loops, and other configurations may be used as would be recognized by those skilled in the art based on the disclosure herein. The four loops321-324 can be activated in different combinations, forinstance loops321 and322,321 and323, or321 and324 can be simultaneously activated. In particular, if a pair of loops is active, with a phase difference between the active loops, the RF field vector may be shifted in order to better read antenna tags that are in different physical orientations. Therefore, use of phased antenna loops may provide better “coverage” for reading tags, when compared to non-phased loops.
• FIG. 11B illustrates a top view ofseveral shelves400,410,420,430,440, and450 supported upon afixture460. Each shelf has, by way of example, four antennae. Forexample shelf410 contains antennae411-414. Furthermore within each shelf and proximate to each of the antennae are one or more RFID tags. InFIG. 11B there are four tags per antennae, the tags being designated a-d. Tags within the shelf are useful for a variety of functions. A smaller or greater number of tags may be used as would be recognized by those skilled in the art.
• For example, ifantenna411 is turned on at a relatively low power, it should be able to read tag411c, which is located, for example, approximately in the center ofantenna411. Of course, one of skill in the art would recognize that depending on the antenna and tag design, at low power, tags at locations closer to the antenna conductor may be used since they would be read more readily. Thus tag411cmay be used to test whetherantenna411 is functioning properly. If the power is increasedantenna411 should also be able to read tags411a, b, andd, which are located near the periphery ofantenna411. By varying the power during a diagnostic or self-check mode, the system should be able to determine how much power is required forantenna411 to function effectively. Shelf tags may be arranged at several distances from the center of each antenna in order to provide this information.
• As the power toantenna411 is increased, it may eventually be able to read shelf tag412bassociated with theadjacent antenna412. The system may thus determine thatantenna411 and412 are adjacent. This information may then be used by the system to determine which adjacent antenna may need to be detuned when a given antenna is operating. The fact thatantennae411 and412 are adjacent could already have been established whenshelf410 was fabricated. However, when several shelves are placed adjacently in a retail store, it may not be possible or convenient to determine in advance which shelves are to be adjacent. The shelf tags may be used to establish which shelves or antennae are adjacent after the system is assembled.
• For example,antenna411 operated at normal power may also detect shelf tag404dassociated withadjacent antenna404 onadjacent shelf400, whose adjacent position may not have been established prior to shelf placement, and shelf tag441aassociated withadjacent antenna441 on theadjacent shelf440 on the opposite side of the gondola (or a common support structure for shelves), whose adjacent position may not have been established prior to shelf placement.
• It is may be designed thatantenna411 operated at normal power or slightly higher power may be able to read further into adjacent antenna areas, for example reading shelf tags404c,412c, and441c. Thus the functionality described herein may be achieved using only a single shelf tag in the center of each antenna.
• Although shelf tags may be useful for the purposes described above, they may slow the system response by increasing the number of tags to be read. It may therefore be a desirable option to use for the shelf tag unique ID serial numbers a specific range of serial numbers that may be directed by the system to a “quiet” mode, that is, not to respond during normal operation, but only to respond during diagnostic or setup operations.
• One or more antennae may be contained or hidden within each shelf. The antenna loops may be made using conductive materials. These conductive materials may include metallic conductors such as metal wire or foil. The conductive material may also be strips of mesh or screen. In one embodiment, the antenna loops may be made of copper foil approximately 0.002″ thick and 0.5″ wide. These loops may be contained within a thin laminate material such as a decorative laminate that is applied to the surface of a supporting shelf material. The loops may also be laminated within glass. The loops may also be adhered to the exterior of a laminated material, glass, or other supporting structure. If additional load bearing support or stiffness is desired, such supporting shelf material may be any material capable of supporting the shelf contents, or providing structural rigidity, as would be recognized by those skilled in the art. Examples of such materials include wood, plastic, rigid plastic foam, glass, fiberglass, or paperboard that is corrugated or otherwise designed to provide stability. An RF-blocking material may be applied to or incorporated into the bottom surface of the shelf, if desired, to prevent detecting RFID tags that may be under instead of the target tags above the shelf. It is to be understood that the intelligent station herein described as a shelf could also be used in a vertical or other angular orientation and the RF blocking material would then be applied in an appropriate orientation to better isolate target tags intended to be read from other adjacent tags.
• An RF-blocking material applied to or incorporated into the bottom surface of the shelf, or present in any underlying metal support such as an existing metal shelf, will substantially prevent RF energy from going “below” the shelf. Alternatively, an RF blocking material may also be incorporated within the interior of a shelf. This is an advantage if it is desired that the shelf sense only tagged items on (above) the shelf. However, a consequence of such an RF-blocking material (whether deliberately provided in the shelf construction, or coincidentally present as a pre-existing shelf structure) is that while nearly completely restricting the RF energy below the shelf, the RF-blocking material under the shelf also reduces the “read range” above the shelf. To compensate for this otherwise reduced read range, a layer of compensating material may be provided just below the antenna loops (that is near the top of the shelf structure). Such a material would be non-conductive and have a high magnetic permeability. Examples are Magnum Magnetics RubberSteel™ or a flexible ferrite magnetic sheet having a high in-plane magnetic permeability. Such an in-plane magnetic permeability is achieved by using an isotropic ferrite sheet, not a conventional anisotropic ferrite sheet whose permeability by design is normal to the sheet. The presence of a layer of this compensating material between the antenna and the RF-blocking material, enables higher flux density between the antenna and the RF-blocking material. Consequently the flux density can be higher above the shelf, thus giving better sensing range (“read range”) for a given shelf thickness.
• The antenna loops, laminated within or attached externally to thin supporting materials, may be disposed in a non-planar form, for example, as curved panels that may be used in certain display cases, beside some clothing racks, or for tunnel readers that may be used at a checkout stand, etc.
• The examples herein discuss loop antennas, which are typically used for readers operating at RF frequencies such as 13.56 MHz. It is possible that items within the intelligent station may contain tags operating at other widely different frequencies, such as 915 MHz, 2.45 GHz, or 125 kHz. The intelligent station may be configured to read these or other frequencies, by providing suitable antennae, for example multiple loop antennae for 125 kHz, and dipole antennae for 915 MHz or 2.45 GHz. Antennae within the intelligent station may be provided for one or several of these frequencies. Each antenna would preferably have its own separate switch and tuning circuit. All intelligent stations would share a single common RF cable, and a single common control cable. Intelligent stations may be constructed so that all areas on each intelligent station may read all desired frequencies (that is each area is served by multiple antennae), or different areas on a given intelligent station may be provided with specific antennae for a specific frequency. Intelligent stations operating at different frequencies could all be interconnected. An intelligent station operating at more than one frequency would require a so-call “agile reader” unit that can be configured operate at more than one frequency.
• In the preferred embodiments, the antenna loops discussed in present application may be placed, for example, upon shelves so they would be placed underneath products by being incorporated into mats that are placed on shelves. The loops are thus encapsulated in an appropriate rigid or flexible substrate well known to those skilled in the art. Examples of suitable substrate material include a laminated structural material, silicone rubber, urethane rubber, fiberglass, plastic, or other similar material that protect the antenna loops and provide some physical offset to prevent electromagnetic interference in case the antennae are placed on metal shelves, walls, or surfaces.
• The encapsulation material or the shelves may be provided with holes or grommets for hanging on vertical surfaces such as the backs of shelves. In an alternate embodiment, the encapsulation material also may be provided with a pressure sensitive adhesive to help attach to a desired surface. The “front” or “shelf” edge of the encapsulation may also be provided with low power light emitting or other display devices that may be turned on by the reader unit or a sequencer unit such as a secondary controller unit within the shelf so that activity of particular display devices may be visually coordinated with the activities of correspondingly positioned reader antennae. Alternatively or in addition, the display devices may also be used to display additional information such as pricing or discounts.
• Besides the ability to read RFID tags, the intelligent station may have additional “peripheral” devices that may communicate information through the digital data cable. For example, the intelligent station system would provide a digital data communication highway for add-on or peripheral attachment devices including but not limited to computer terminals, display devices, modems, bar code readers, temperature sensors, locking devices for enclosed or tethered merchandise, etc. The digital data communication highway may be incorporated into the wiring system that sends digital control and data information betweencontroller124 andsecondary controllers125, or it may be one or more separate digital data communication highways that are made up of wiring that runs through and connects between the stations, with the stations provided with ports through which to connect the add-on or peripheral devices. The digital data communication highway facilitates the transmission of data in both directions between the intelligent stations system (including thecontroller124 and secondary controller125) and the electronic network. Electrical power may also be provided for the add-on or peripheral devices through wires that run through the stations.
• It should be understood that, whether or not add-on or peripheral devices are used, electrical power other than RF power may be used by the stations, for example direct current (DC) used by thesecondary controller125, and by the switches and tuning electronics. Such electrical power may be provided by one or more dedicated wires, or it may be incorporated into the digital communication highway or with an RF cable.
• As an example, an RF cable may comprise two conductors, for example in a coaxial cable, the center conductor and the sheath conductor. The RF cable carries an RF signal. A DC voltage may be superimposed on the RF signal, in the same RF cable, to provide DC power to intelligent stations. If the DC voltage, for instance 18 volts DC, is higher than needed for some devices in the intelligent station (for instance 5 volts DC), a voltage regulator may be used to decrease the voltage to within usable limits.
• As a further example, digital communications may be carried on the same RF cable. For instance, the DC voltage superimposed on the RF cable may be switched between two DC levels (for example 18 volts DC and 12 volts DC) to accomplish non-RF digital communications on the RF cable Therefore, a primary controller may send information to secondary controllers by using such digital communications.
• As a further example, a secondary controller may send information to a primary controller in digital form over an RF cable by switching on and off an electrical load to thereby drain current from the RF cable. This in turn may be sensed at the primary controller. The use of voltage level and the use of load level may be done simultaneously to achieve two-way digital non-RF communication through the RF cable.
• As another example, in the shelf embodiment, another device that may advantageously be incorporated into the shelf is a plug-in bar code reader that could interface to thesecondary control unit125. When the shelf was being stocked, the bar code reader could be used to scan the packages being placed on the shelf. The bar code data would then be sent back to the electronic network along with the unique RFID tag serial number. If the product identity defined by the bar code was not previously associated with the unique RFID tag serial number, the association would now be completed within the data store. Otherwise the bar code scan could serve as a verification of the data store information. The use of the bar code device would further enable the shelf to provide benefits even during staged introduction of RFID tagged merchandise. By comparing the number of items stocked onto the shelf (as identified by the bar code scanner in conjunction with a simple numeric keypad), against the number of same items sold (as determined by existing scanners at the checkout line) it could be determined approximately how much merchandise remained on the shelf, and whether restocking was necessary. Likewise barcode scanning at the shelf itself could be utilized to provide current pricing information retrieved from the electronic network and displayed through alphanumeric displays at the shelf.
• In another embodiment, the shelf or intelligent station may be provided with environmental sensors, to monitor or measure, for example, temperature, humidity, light, or other environmental parameters or factors. Since the system is able to determine what items are on the shelf, the system could keep track of the environment for each item and provide a warning if environmental conditions were out of limits for specific types of items. Separate limits could be defined for each group of items.
• One or more proximity sensors, for example, infrared sensors or capacitive sensors, may be located on the shelf to detect the presence of a shopper and determine whether to increase the reading frequency at that shelf in order to give the shopper rapid feedback when an item is moved from the shelf. The means of detecting a shopper would be located at the front edge of the shelf, where they would not be obstructed by merchandise. Infrared or capacitive sensors could sense the presence of a shopper by detecting body heat from the shopper, or a change in local capacitance due to the shopper being in front of the shelf, or the shopper's hand or arm, or merchandise, moving near the front of the shelf. Other means of detecting the presence of a shopper could include visible or infrared light sensors along the front edge of the shelf to detect the shadow of a hand or arm reaching for merchandise on the shelf. The light source in this case could be ambient visible light, or visible or IR light from sources located below the next higher shelf, or from sources overhead or on the ceiling of the store. Store security cameras could also be used to detect the presence of shoppers and to direct the intelligent station to increase reading frequency. Likewise, audible/visual signals or displays or can be activated when a shopper is sensed and for some time thereafter rather than being activated at all times in order to conserve power and component life. Likewise information regarding the proximity of a shopper to the shelf could be relayed back to the electronic network to help analyze shopper traffic patterns, or length of time spent at a particular shelf. The shopper location data could also be fed to store security systems for use in conjunction with scanning patterns of store surveillance cameras.
• Likewise the shelf data relayed back to the electronic network can be used to determine if an unusually large number of items are suddenly removed from the shelf. If this occurs, a security camera can be directed at the shelf to take a picture of the shopper who removed the items. If the items are not paid for when the shopper leaves the store, appropriate action can be taken to stop the theft.
• Another device that may be incorporated into the shelf is a Hall effect or other similar proximity type sensor to detect movement of tags or presence of a shopper. This information may be used similarly to that described in the preceding description regarding an infrared sensor.
• Another use of the shelf would be to detect the presence of “customer tags” associated with shoppers, that could be used to help shoppers find predetermined merchandise items, such as the correct size of clothing items, whereby visual or audible indicators on the shelf could be activated to direct the shopper toward the desired items. Also the “customer tag” when placed on a shelf where a desired item was out of stock, could be used to give the customer a “rain check” and or discount on the item when it came back into stock, or information about the item being in the stock room, at another store, or on order. This could be useful to track when a shopper did not purchase an item because it was out of stock.
• Another use of the shelf would be to provide “feedforward” information to predict when more cashiers would be required at the checkout lanes, or when more stockers were required. This could, for example, be done by monitoring the amount of merchandise being removed from shelves, and thereby deducing the volume of merchandise that would be arriving at the checkout lanes. The storekeeper or store manager thereby could schedule the checkout or restocking personnel to optimize how their time is spent, help schedule break time, etc.
• Another use of the shelf could be to detect the presence of a “stocking tag” or “employee tag,” or a pushbutton or keyed input sequence, to alert the system that the shelf is stocked completely and the database is made aware that the current stock level is the full or target level. This method could be used when item stocking patterns were changed, to update the target level.
• The shelf system could be used to suggest, for all shelves covered by the system, based on the price, traffic, and shelf space, the most optimal stocking pattern, which may involve changing the target inventory for all items. Calculating such a stocking pattern would require knowledge of how many of each SKU item would fit on a given shelf area, and how much shelf area was covered by each shelf antenna.
• In one aspect of the present invention, it would be advantageous for the shelf system to know the physical location of each shelf, which may not necessarily be obvious even from unique Ethernet or RS-485 addresses or other networking addresses. Therefore, the present invention contemplates incorporating a GPS transducer into each shelf. A more practical solution may be to, instead, provide a portable GPS unit that could be plugged into a USB port (or other similar compatible port) on each shelf, when the shelf was assembled, to identify its location. For example, a GPS unit could be combined with the servomechanical tuning unit used to set up the shelf after its installation.
• Alternately, a GPS unit with a programmable RFID tag could be placed upon a shelf and communicate back to the main controller, through the RFID system, what the coordinates of the shelf are. One way of accomplishing this would to use a GPS system connected to a specialized RFID tag having additional storage blocks for information besides its unique serial number. Such a tag would use an integrated circuit with connections to its tag antenna also to communication circuitry to receive data from an outside source, such as the GPS system. The GPS system could be configured to write the spatial coordinates in the additional storage blocks. A known serial number or numbers could be used in the specialized RFID tag, and the RFID system, upon detecting such a specialized RFID tag could interrogate the tag to determine the stored spatial coordinates and associate then with the shelf and antenna that was being read.
• The antenna shape need not be confined to single-loop antennae. A single loop antenna is a form factor that may typically be used with high RFID frequencies such as 13.56 MHz. Amulti-loop antenna1215 may be used at a lower frequency such as 125 kHz, or to permit lower current operation at high frequencies such as 13.56 MHz. The use of lower current antennae may permit using lower power switching components. Forming multi-loop antenna may require antenna components such as the wire in the loops to be in close proximity to one another, and therefore the wire may preferably be insulated.
• Tuning components associated with the RFID antennae, for example, rotary trim capacitors or capacitor banks, may require access during use. Suitable access may be provided, for example in a shelf embodiment, by providing removable cover devices, or holes in the shelf
• For attaching conductive antenna materials onto supporting laminate or other structures, a variety of methods may be utilized. For example, a metal foil may be laid down onto a substrate in web form (such as a web of paperboard) or planar form (such as a sheet of paperboard, sheet of laminate, wood or plastic board, etc.) by an automated machine using two or three dimension positioning mechanisms to feed the foil from a reel onto the substrate in the desired antenna pattern.
• If the supporting material is wood, a milling machine may be used to form grooves into which conductive wire may be secured in order to form antenna loops. The same method may be used if the supporting material is plastic, or, a heated pattern may be pressed into the plastic to form grooves in which conductive wire may be secured. A plastic substrate may be molded with grooves to hold wire conductors, or the plastic substrate may be molded with a repeating rectilinear pattern of perpendicular grooves that permit forming antenna loops in a large number of patterns. In any of these methods, holes may be drilled, punched, or molded for securing the ends of the antenna wires. These holes may extend through the substrate to become accessible for connection or insertion into tuning circuits used to tune the antenna loops.
• Another method of forming antenna loops is to wrap the conductive wire around a series of pins similar to a loom, then invert the loom and press the conductors onto a substrate. The substrate may be precoated with adhesive to hold the conductors when the loom is removed. Alternately the substrate may be soft enough to allow the conductors to be pressed into the surface of the substrate. Alternately the substrate may be a thermoplastic and the conductors may be preheated so that they partly melt the substrate on contact and become embedded in it's the surface of the substrate. The pins used on the loom to form the antenna loops may optionally be spring-loaded so that when the loom is pressing the conductors onto the substrate, the pins may optionally retract into the loom.
• In more detail,FIG. 12 shows one method of making a wire antenna.FIG. 12 is not intended to limit the present invention since one skilled in the art would recognize various modifications, alternatives, and variations. A substrate1100 is provided, such as a wood, plastic, rubber, high density foam, or similar material.Grooves1110 are provided in the substrate, typically in a grid pattern. These grooves may be made by machining, molding such as by hot or cold-pressing or injecting molding, casting, hot branding (for example with wood), etc. Pressing methods may use platen (stamping) or rotary devices. Preferably holes1130 are provided at intersection points in the grooves, by the same methods or by drilling or punching. A large part of the area on substrate1100 is still occupied by theareas1120 between grooves. Thus the substrate1100 still has an essentially planar upper surface, so that loads may be borne by the surface and a covering, film, laminate, or veneer may be applied to provide a planar finished surface. Theareas1120 are also known to be unoccupied by antenna wires, and these areas may be provided by casting, drilling, punching, etc. with holes to accommodate screws or bolts to attach to other structures. The holes may also be used for attachments such as pegboard or display hooks, or through holes for wiring, ventilation, sound from loudspeakers, placement of small lights, etc.
• Antenna loop1200 is shown that has been formed by placing or pressing wire of a suitable diameter into some of thegrooves1110. The ends1201 of the antenna loop are held in place by securing them intoholes1130. The holes can be entirely through substrate1100, so that they may be connected to circuitry on the other side of the substrate. Likewiseantenna loop1210 is shown being formed, withwire end1211 already secured in one hole andwire end1212 shown ready to be secured into another hole.
• Besides simply pressing bare wire through the holes to secure the ends, the wire may be precut to the needed length, and the ends fitted withgrommets1140, buttons, or other mechanical devices that fit intoholes1130. These grommets may be soldered onto the wire for better conductivity. As an alternative to inserting them intoholes1130, the grommets may be slightly larger diameter than the width of thegrooves1110, so that the grommets will only fit at points where two grooves intersect, as shown inFIG. 12A. Alternately during forming of the groove pattern, the intersection points may be made larger than the groove widths as shown inFIG. 12B, to hold alarger grommet1141. The grommets may be bar shaped (1142) or tee shaped (1143) to fit in the intersection points as shown inFIG. 12C. They may also be cross-shaped. They may be fitted with pins to protrude down into or through substrate1100, or to extend upward out of substrate1100. The pins may fit into sockets on, or holes in, the circuit boards. The grommets (e.g.1140 or1141) may be hollow to accept other wiring or pins. They may incorporate externally threaded pins or internally threaded holes. The grommets likewise may incorporate internal or external barbs or spring-loaded parts to hold them in place or to assist in connecting to external circuitry. The antenna wires attached to the grommets may also be secured by barbs.
• The substrate1100 may be provided with recesses (not shown) in which to position circuitry (not shown), and such circuitry installed before or after the wires, and the wires attached to the circuitry by soldering or use of grommets, barbs, etc.
• Instead of thegrooves1110 forming a regular grid or criss-cross pattern, which allows for multiple antenna patterns to be created, the grooves can instead be provided in “custom” form to comprise only the grooves desired for the actual antennae to be produced.FIG. 13 shows such an embodiment. The grooves, for example1220 and1230, can be formed by the same methods described above, as can theholes1221 and1231.
• Since the grooves and holes hold the wire securely, the wire may be easily inserted by hand into the substrate, or the process may be mechanized. After all desired antennae have been formed in the substrate, any open grooves may be filled with plastic or any other suitable material. A covering laminate, film, or other layer may then be applied on top of the substrate. This covering may be an injection-molded layer of material, or melt-cast layer, or liquid cast layer that cures by chemical reaction or heat (such as an epoxy material or silicone compound), or evaporation (such as a latex material).
• The combined substrate and covering then comprise an antenna mat. Depending on the materials, the antenna mat may be flexible or rigid. The antenna mat may also be attached to a planar or non-planar supporting material such as a wood, plastic, fiberglass, etc. board.
• The antenna shape need not be confined to single-loop antennae.FIG. 13A showssingle loop antennae1200 and1210, a form factor that might typically be used with mid range RFID frequencies such as 13.56 MHz. Also shown is amulti-loop antenna1215 that might typically be used with a lower frequency such as 125 kHz. Formingmulti-loop antenna1215 may require the wire loops to be in close proximity to one another, and therefore the wire may preferably be insulated. It may be desired to have awire crossover1216 as shown, or no crossover as denoted by dottedline1217. The distance between grooves may have to be narrower for multi-loop antennae. Also shown is the shape of adipole antenna1218 that might typically be used with higher frequencies such as 915 MHz or 2.45 GHz. The ends1219 shown for the dipole antenna are bent to denote a method for holding these otherwise loose ends by inserting the ends into holes in the substrate during fabrication.
• In the embodiment ofFIGS. 12 and 13, the grooves are created before the antenna wires are set in place. A different embodiment is shown inFIG. 14. Anupper plate1300 is provided which has a pattern ofholes1301 for holdingpins1302. The pins may be threaded and the holes tapped so that the pins may be secured by screwing them into the holes. Thus the number and placement of the pins may be varied.
• Alower plate1310 is provided with matchingholes1311. When theplates1300 and1310 are brought together as shown at arrow “A”, pins1302 protrude throughholes1311.Pins1302 may then be used to define the corners of wire antennae that are wound around the pins under thelower plate1310. Forexample antenna1240 is formed using pins to hold the wire at three corners. At the fourth corner, the two wire ends1241 are inserted up throughopen holes1311 in thelower plate1310. Anotherexample antenna1250 is formed using pins at all four corners.Grommets1251 attached to the ends of the wire loop are held over two additional pins. Instead of securing the wire ends within the plate area, they may also extend beyond the plate as shown by the dotted lines at1252. In this case the wire ends would be secured by other means (not shown).
• The combinedassembly1330 ofupper plate1300 andlower plate1310 with attached pins, wires, grommets, etc. is then inverted oversubstrate1320 as shown by arrow “B”. Theantennae1240 and1250 are transferred onto thesubstrate1320 by one or more of the following or similar methods.
• a) An adhesive coating or film is applied to thesubstrate1320. The combinedassembly1330 is lowered onto thesubstrate1320, andlower plate1310 is pressed against the substrate. Theantennae1240 and1250 adhere to the adhesive. Ifupper plate1300 is lifted slightly during the pressing step, thepins1302 will not penetrate thesubstrate1320. Ifupper plate1300 is also kept under downward pressure, thepins1302 will make holes in thesubstrate1320. Anygrommets1251 will be pressed into the substrate. After the adhesive set, the combinedassembly1330 is lifted, leaving the antenna pattern attached tosubstrate1320.
• b) Method (a) may be used, with sufficient pressure to force the antenna wires partly or completely below the surface of thesubstrate1320. This method could be used, for example, with a highdensity foam substrate1320 which requires minimal force to press the wires below the surface.
• c) Method (b) may be used, with thewires1240 and1250 andgrommets1251 heated to a temperature above the softening point ofsubstrate1320, so that on contact and pressure, the substrate is softened or melted slightly to accept the wires and grommets. One method of heating the wires is to pass an electric current through them before or during pressing against the substrate. Theupper plate1300 may be released during the pressing step so that thepins1302 retract and do not penetrate intosubstrate1320.
• d) The substrate instead of being asolid material1320 may at this point be cast onto the wires by liquid casting of chemical, thermal, evaporative or otherwise setting material, or by injection molding, of a material to the lower surface oflower plate1310.
• Lower plate1310 andpins1302 may be precoated with a release agent to prevent sticking. Such a release agent would be applied before the wires are attached, so that release agent is not applied to the wires. Also,lower plate1310 may be a non-stick material, for example Teflon or coated with Teflon or a similar non-stick material. If an injection molding is used,lower plate1310 may be cooled by internal passageways to speed up cooling of the injection-molded material.
• After these steps, theantennae1240 and1250 may be attached to circuitry using wire ends1241 or1252, orgrommets1251.
• In all embodiments, it is understood that the wires may be bare (except at crossovers) or insulated. The cross section of the wires may be a solid cylinder as is typically the case with wire, but it may also be square, rectangular, oval, U shaped or channel shaped, vee-shaped, etc. The main requirement of the wire is that regardless of shape it must be conductive and must have a shape and cross-sectional stiffness that promotes its being held in the grooves. The wire may be single conductor (typically known as “solid” conductor), or multistrand. It may be twisted or woven. It may be coaxial cable, in which case the external braid would be used as the active conductor for the RF signal.
• FIG. 15 is a diagram that illustrates a device and method of applying foil tape ribbons to a web or planar substrate to form foil antennas according to the present invention. Such foil antennae have several uses, for example, they may be used as transceivers or readers for communicating with RFID tags in RFID systems that may be used for inventory control.FIG. 15 is not intended to limit the present invention since one skilled in the art would recognize various modifications, alternatives, and variations. Asubstrate2100 is provided. This may be in web form, as shown, in whichcase traction rollers2110 or other means may be provided to move the web. In the example shown inFIG. 15, such movement would be discontinuous. Theweb2100 would be indexed forward a distance, then stopped while one or more conductive pathways were deposited ontosubstrate2100. Once the conductive pathways had been deposited onsubstrate2100, the web would be indexed forward again and the cycle repeated.
• Asupport plate2120 is provided under the substrate. Thissupport plate2120 may incorporate a vacuum hold-down system (not shown) to temporarily fix thesubstrate2100 to thesupport plate2120. Thesupport plate2120 itself may also be movable in the X and Y directions to assist in the process of depositing conductive pathways.
• An applicator means2200 is provided for depositing theconductive pathways2300. Thisapplicator2200 will be described in more detail later. Anx-y stage2400 is provided for movingapplicator2200. The x-y stage may include aframe2401, a positioning means2402 that moves in the principal substrate axis (“x” or “machine” direction), and a second positioning means2403 that moves in a perpendicular axis (“y” or “cross” direction.) A rotational positioning means2404 may be provided to turn theapplicator2200 in any angle relative tosubstrate2100, to facilitate the operation ofapplicator2200. It is anticipated that thesubstrate2100 movement and theapplicator2200 movement will be automated by computer means that control motors drivingtraction rollers2110, and positioning means2402,2403, and2404, in addition to more controls withinapplicator2200.
• InFIG. 15 the x and y positioning means2402 and2403 are shown as rack and pinion gearing, but could include other means such as cables, linear motors, stepping motors, or other means that can achieve fairly repeatable positioning.
• FIG. 16 shows another method of depositing conductive pathways on a substrate to a form foil antenna.Support member2500 extends across the substrate and holds two or more stationary positioning means2501 that inturn support applicators2200. The stationary positioning means2501 can be moved by hand across thesupport member2500, then fixed in place for example with a thumbscrew. Enough stationary positioning means2501 withapplicators2200 are provided to lay down along the machine direction (x) as many lengthwiseconductive pathways2301,2302 as needed. In the example shown, lengthwiseconductive pathway2302 is provided with a skippedarea2303 that will be used for connection to external circuitry.
• Support member2510 extends across the substrate and holds a traversing means2511 that in turns supports anotherapplicator2200. Traversing means2511 can move on demand across the substrate in the cross direction (y) to deposit crosswaysconductive pathways2304 and2305 that connect the lengthwiseconductive pathways2301,2302.
• Operation according toFIG. 16 is therefore as follows: Thesubstrate2100 is moved forward by traction rollers2110 (or by movement of support plate2120). Meanwhile theapplicators2200 attached to stationary positioning means2501 deposit on demand lengthwiseconductive pathways2301,2302 that may contain skippedareas2303.
• At the appropriate times, thesubstrate2100 movement is paused so that theapplicator2200 attached to traversing means2511 can deposit crosswiseconductive pathways2304,2305. The pause in the X direction movement ofsubstrate2100 may occur in the middle of the process of depositing one or more of the lengthwiseconductive pathways2301,2302. Alternately, for depositing the crosswiseconductive pathways2304,2305,applicator2200 may be fixed in position and the Y direction movement provided by movement ofsupport plate2120.
• The decision of whether to movesubstrate2100 in web form or in sheet form will depend on several factors. The substrate may be available in roll form advantageous to web handling, or in cut form advantageous to sheet handling. Some substrates may not be flexible enough for handling in web form, for example thick sheet substrates or substrates that have been partly or completely laminated and are no longer flexible.
• The decision of which applicator system to use will also be made based on several factors. The single head applicator design ofFIG. 15 minimizes the number of applicators, but slightly complicates the applicator positioning. It may be slightly slower than a multiple applicator design. However, it is quite flexible in terms of making customized products, since every conductive pathway may be customized. The multiple applicator system ofFIG. 16 simplifies the positioning of the applicators, and may improve speed for long production runs of single designs.
• Instead of moving the applicators as inFIGS. 15 and 16, the substrate itself could be moved in the x-y plane to help create the conductive pathways. This would typically require more floor space than when moving the applicators, and it would be complex if the substrate was in roll form.
• FIG. 17 shows a cross section of anapplicator2200 for depositing conductive pathways.FIG. 17 is not intended to limit the invention since one skilled in the art would recognize various modifications, alternatives, and variations. As shown in the embodiment ofFIG. 17, theapplicator2200 would move to the right relative tosubstrate2100. Asupply roll2210 provides a continuousconductive strip2211 through a pair of feed rolls2212 that are computer controlled to provide thecontinuous strip2211 only when demanded. Thestrip2211 goes into achute2213 and past acutter2214 that is computer controlled and may be turned at any angle to provide angled cuts if desired. Thestrip2211 continues forward and out of theapplicator2200, at which point anoptional release liner2215 can be removed and wound aroundroller2216 to be taken up ontotension winding roll2217.
• A second,optional supply roll2220 provides a continuousinsulating strip2221 through a pair of feed rolls2222 that are computer controlled to provide the insulatingstrip2221 only when demanded. Thestrip2221 goes into achute2223 and past acutter2224 that is computer controlled. Thestrip2221 continues forward and out of theapplicator2200, at which point anoptional release liner2225 can be removed and wound aroundroller2226 to be taken up ontotension winding roll2227.
• Apressure device2230 is provided to push thestrips2211 and/or2221 onto thesubstrate2100. The pressure device may be a wheel or roll as shown, or a sliding member, or a reciprocating clamping means. Thepressure device2230 may be heated to help set an adhesive integral tostrips2211 or2221, or provided externally as described later. Thepressure device2230 may be patterned or knurled, for example to help press thestrips2211 or2221 onto thesubstrate2100, or even to slightly crimp thestrips2211 or2221 into the material of thesubstrate2100. This might remove the need for adhesive, at least in sheet-fed operations. It is also envisioned thatstrip2211 may be perforated with holes to improve the adhesion of resin between layers of substrate in the final laminate, even in the areas where thestrip2211 exists.
• Ahole punch2240 is provided to perforate thesubstrate2100 on demand to create openings through which electrical connections may be made to theconductive strip2211. Preferably thehole punch2240 is provided with an internal vacuum connection to remove the waste substrate material created during a hole punching operation.
• Anadhesive dispenser2250 is provided to dispenseglue2252 throughneedle2251, in order to holdstrip2211 or2221 to the substrate. Preferably the adhesive is a rapid set material such as a hot melt glue, heat set glue, or epoxy. This adhesive is deposited on demand under computer control to be present under thestrip2211 or2221, but not deposited if no strip is deposited in a given area. Any adhesive that may be used should not degas when pressed at high temperature, otherwise the integrity of the laminate may be compromised.
• Theconductive strip2211 or insulatingstrip2221 may also be provided with their own adhesive layers to attach it to thesubstrate2100.
• The adhesive used to attach thestrips2211 and2221 tosubstrate2100 would typically be non-conductive, since conductive adhesives are more expensive. However, it will be necessary in some places to electrically join parts of theconductive pathway2300, and for this a conductive adhesive or material would be required. For simplicity it might be decided to useconductive strip2211 with an integral conductive adhesive, but this would be expensive. Another solution is to provide within the applicator2200 areservoir2260 of conductive adhesive to be applied throughneedle2261 indroplet form2262. Adrop2262 of the conductive adhesive could be applied on top of a previous segment ofconductive trace2300, just before starting the next segment on top of the previous segment. The action of pressingmeans2230, with heat and pressure, would then electrically join the two segments. Theconductive adhesive drop2262 could be a drop of metal solder in either a low melting form, or in suspension (either form would be remelted by the pressure means2230).
• FIG. 18 illustrates a method using the apparatus shown inFIG. 15 to lay down a simple rectangular conductive pathway. The steps are as follows
• Substrate2100 is indexed forward in the x direction byrollers2110.
• Using X positioning means2402 and y positioning means2403, theapplicator2200 is moved to point “a” and “h” where thehole punch2240 makes two holes in thesubstrate2100.
• Using X positioning means2402, theapplicator2200 is positioned to point “b”.
• Theapplicator2200 moved by X positioning means2402, uses internal devices2210-2217 to lay down aconductive pathway2300 from points “b” to “c.” During this operation,cutter2214 cuts thestrip2211 at a precisely determined moment so that theconductive pathway2300 ends at point “c.” Note that the beginning of theconductive strip2300, at point “b,” slightly overlaps the hole punched at “a.”
• X positioning means2402 is used to move the conductiveadhesive applicator2261 to point “c”, where a drop of conductive adhesive2262 is placed on the end of theconductive pathway2300.
• Rotational positioning means2404 rotates theapplicator2200 by 90 degrees so that it can run in the cross direction Y.
• X and Y positioning means2402 and2403 are used to place theapplicator2200 to point “c.”
• Theapplicator2200 moved by Y positioning means2403, uses internal devices2210-2217 to lay down aconductive pathway2300 from points “c” to “d.” During this operation,cutter2214 cuts thestrip2211 at a precisely determined moment so that theconductive pathway2300 ends at point “d.”
• Y positioning means2403 is used to move the conductiveadhesive applicator2261 to point “d”, where a drop of conductive adhesive2262 is placed on the new end of theconductive pathway2300.
• Rotational positioning means2404 rotates theapplicator2200 by 90 degrees so that it can run in the machine direction X.
• X and Y positioning means2402 and2403 are used to place theapplicator2200 to point “d.”
• Theapplicator2200 moved by x positioning means2402, uses internal devices2210-2217 to lay down aconductive pathway2300 from points “d” to “e.” During this operation,cutter2214 cuts thestrip2211 at a precisely determined moment so that theconductive pathway2300 ends at point “e.”
• X positioning means2403 is used to move the conductiveadhesive applicator2261 to point “e”, where a drop of conductive adhesive2262 is placed on the new end of theconductive pathway2300.
• Rotational positioning means2404 rotates theapplicator2200 by 90 degrees so that it can run in the cross direction Y.
• X and Y positioning means2402 and2403 are used to place theapplicator2200 to point “e”
• Theapplicator2200 moved by y positioning means2403, uses internal devices2210-2217 to lay down aconductive pathway2300 from points “e” to “f.” During this operation,cutter2214 cuts thestrip2211 at a precisely determined moment so that theconductive pathway2300 ends at point “f.”
• Y positioning means2403 is used to move the conductiveadhesive applicator2261 to point “f”, where a drop of conductive adhesive2262 is placed on the new end of theconductive pathway2300.
• Rotational positioning means2404 rotates theapplicator2200 by 90 degrees so that it can run in the machine direction X.
• X and Y positioning means2402 and2403 are used to place theapplicator2200 to point “f.”
• Theapplicator2200 moved by x positioning means2402, uses internal devices2210-2217 to lay down aconductive pathway2300 from points “f” to “g.” This last portion of thepathway2300 is not yet completed inFIG. 18. During this operation,cutter2214 cuts thestrip2211 at a precisely determined moment so that theconductive pathway2300 will end at point “g.” Note that the end of theconductive pathway2300, at point “g”, will slightly overlap the second hole punched at point “h.”
• Steps2-20 are repeated for eachconductive trace2300 to be applied tosubstrate2100 on the exposed area of the substrate. Then the substrate is indexed forward again starting withstep1.
• Instead of forming theconductive trace2300 by connecting separate pieces of thefoil strip2211, theconductive trace2300 may be formed from acontinuous strip2211. Instead of usingcutter2214 to cut thefoil2211 between segments at each corner, thestrip2211 may be automatically folded over. For example, this may be done by turning rotary positioning means2404 through a 90 degree turn and pressing down on the folded corner so that thetrace2300 lays flat at the corner.
• FIG. 18A shows the result. The folded corner will have a maximum of three overlapping thicknesses of foil.FIG. 18B shows the result if the foil is at the same time twisted 180 degrees to invert the tape. (This would require another positioning means, not shown. Inverting the tape may be undesirable if the tape has an adhesive coating, since the adhesive will now be facing away from the substrate). The folded corner will have a maximum of two overlapping thicknesses of foil.
• FIG. 19 shows an embodiment where aconductive trace2300 being laid down overlaps a previous conductive trace.
• Before the overlapping segments of the secondconductive trace2300 are laid down, strips “I” and “J” of non-conductive film are laid down over the first trace, usingapplicator2200. These insulating strips “I”and “J” prevent electrical contact between the separate conductive loops that are formed by theconductive trace2300. In similar manner, “cross-over” circuitry can be laid down.
• It is anticipated that thesubstrate2100 withconductive traces2300, whether in sheet or web form, may be incorporated into a laminated structure that may be used in a shelf, panel, enclosure, spaces, or other form. An example of such a laminated structure is shown inFIG. 20. Thesubstrate2100, which may be a paper or paperboard material, is joined withadditional plies2600 and2601 of similar or dissimilar materials, for example saturating Kraft paperboard soaked in resin, and formed under heat and pressure into alaminate2610. Usually the outer ply orplies2601 on the first surface opposite from thesubstrate2100 would be a decorative material that would for the “outside” of the resulting product. Depending on the orientation of theouter substrate layer2100, this laminate2610 contains on its second surface, or just inside that surface, theconductive traces2300 already described. The laminate2610 may then be glued onto a heavier supportingmember2620, such as a board made of wood, plastic, particle board, corrugated cardboard, Westvaco Core-board, or similar. The surface of laminate2610 that is proximal to theconductive traces2300 is preferably glued to the supportingmember2620. Thus the full thickness of the laminate2610 protects theconductive traces2300 from abrasion during use of the resulting combinedstructure2630, formed of laminate2610 and supportingmember2620.
• A conductive or metallic backplane2625 may optionally be applied to the bottom of the shelf to block RF energy from going below the shelf, thus making the shelf operate with approximately the same RF behavior regardless whether or not it was supported by metal brackets or placed upon an existing metal shelf.
• FIG. 21 shows how, before the supportingmember2620 is glued to the laminate2610, it is preferable to place inside the supportingmember2620 one or more electronic circuits that communicate with theconductive traces2300, either by the latter being directly exposed, or through the perforations already described. To accommodate electronic circuits recesses may be milled into the surface of the supportingmember2620. A numerically controlledmilling machine head2700 could be used in a positioning system similar in design to the system shown inFIG. 15 for laying down theconductive traces2300, and could be run by a same or similar computer control system that would control the location and depth of recesses. For example, at the edge of the supportingmember2620 is shownrecess2631 for accommodating anexternal connector2632. Within supportingmember2620 is shownrecess2633 for containingelectronic circuitry2634 such as switching and tuning circuitry. Spanning supportingmember2620 is shownrecess2635 for containing wires or cables to connect the circuitry components. Theelectronic circuitry2634 may incorporate spring loadedcoils2637 orfingers2638 to make contact with theconductive traces2300 onsubstrate2100 that is part of laminate2610 to be attached to supportmember2620. Said electrical contact could be by pressure, by conductive adhesive or paste, or by solder melted during the lamination process. Themilling head2700 may be used to makegrooves2639 for access of tuning tools such as small screwdrivers for adjusting trim capacitors withincircuitry2634.
• Tuning components withincircuitry2634, for example rotary trim capacitors (not shown) may require access after assembly, which can be provided through openings such asholes2611 drilled through laminate2610 inFIG. 20, orholes2612 drilled through supportingmember2620 inFIGS. 20 and 21.
• FIGS. 3A and 3B are block diagrams illustrating a preferred embodiment of an inventory control system that uses intelligent shelves in accordance with the present invention. As shown inFIG. 3A, each of the several intelligent shelves501a-501nand502a-502nprovided according to the present invention havemultiple antennae200 connected to areader unit120 through asingle transmission cable222. Thereader units120 controls the activation of theconnected antennae200 either sequentially, or simultaneously with a phase difference, to determine item information from RFID tags associated with respective items being inventoried. Therefore, thereader units120 are able to extract inventory related information for each of the RFID tagged items stored in the respective shelves. For simplicity,FIG. 3A shows only two groups of shelves, each group having its own reader unit, the groups being501a-501nand502a-502nrespectively. However, one skilled in the art would recognize that many such groups of shelves could be a part of an inventory control system provided by the present invention. For example, all the shelves in one or more warehouses could be grouped to provide hundreds or even thousands of groups of shelves that could be connected together to form an inventory control system as provided by the present invention.
• It should be understood that while the preferred embodiment of the inventory control system and method utilizes a multiple antenna RFID detection system with asingle transmission cable222 corresponding to the embodiment ofFIG. 6, all the other embodiments of the multiple antenna RFID system disclosed herein may also be used with the inventory control system and method according to the present invention. Therefore, for example, the RFID detection systems disclosed inFIGS. 7 and 8 may also be used with the inventory control system and method of the present invention. In such embodiments, for example, the unmodulated RF system may be used first to warm up the tags before the modulated RF system is used to extract the inventory related data from the RFID tags.
• As shown inFIG. 3A, the item information data collected by thereader units120 from each of the intelligent shelves501a-501nand502a-502nis transmitted to an inventorycontrol processing unit550. The inventorycontrol processing unit550 is typically configured to receive item information from the intelligent shelves501a-501nand502a-502n. The inventorycontrol processing unit550 is typically connected to the intelligent shelves over anelectronic network525 and is also associated with anappropriate data store555 that stores inventory related data including reference tables and also program code and configuration information relevant to inventory control or warehousing. The inventorycontrol processing unit550 is also programmed and configured to perform inventory control functions that well known to those skilled in the art. For example, some of the functions performed by an inventory control (or warehousing) unit include: storing and tracking quantities of inventoried items on hand, daily movements or sales of various items, tracking positions or locations of various items, etc.
• In operation, the inventory control system would determine item information from the intelligent shelves501a-501nand502a-502nthat are connected to the inventorycontrol processing unit550 through anelectronic network525. In one embodiment, the various intelligent shelves501a-501nand502a-502nwould be under the control of inventorycontrol processing unit550 that would determine when thereader units120 would poll theantennae200 to determine item information of items to be inventoried. In an alternate embodiment, thereader units120 may be programmed to periodically poll the connected multiple antennae for item information and then transmit the determined item information to the inventory control processing unit using a reverse “push” model of data transmission. In a further embodiment, the polling and data transmission of item information by thereader units120 may be event driven, for example, triggered by a periodic replenishment of inventoried items on the intelligent shelves. In each case, thereader unit120 would selectively energize the multiple antennae connected to it to determine item information from the RFID tags associated with the items to be inventoried.
• Once the item information is received from thereader units120 of the intelligent shelves501a-501nand502a-502nof the present invention, the inventorycontrol processing unit550 processes the received item information using programmed logic, code, and data at the inventorycontrol processing unit550 and at the associateddata store555. The processed item information is then typically stored at thedata store555 for future use in the inventory control system and method of the present invention.
• One skilled in the art would recognize that inventorycontrol processing unit550 could be implemented on a general purpose computer system connected to anelectronic network525, such as a computer network. The computer network can also be a public network, such as the Internet or Metropolitan Area Network (MAN), or other private network, such as a corporate Local Area Network (LAN) or Wide Area Network (WAN), or even a virtual private network. A computer system includes a central processing unit (CPU) connected to a system memory. The system memory typically contains an operating system, a BIOS driver, and application programs. In addition, the computer system contains input devices such as a mouse and a keyboard, and output devices such as a printer and a display monitor.
• The computer system generally includes a communications interface, such as an Ethernet card, to communicate to theelectronic network525. Other computer systems may also be connected to theelectronic network525. One skilled in the art would recognize that the above system describes the typical components of a computer system connected to an electronic network. It should be appreciated that many other similar configurations are within the abilities of one skilled in the art and all of these configurations could be used with the methods and systems of the present invention. Furthermore, it should be recognized that the computer system and network disclosed herein can be programmed and configured as an inventory control processing unit to perform inventory control related functions that are well known to those skilled in the art.
• In addition, one skilled in the art would recognize that the “computer” implemented invention described herein may include components that are not computers per se but also include devices such as Internet appliances and Programmable Logic Controllers (PLCs) that may be used to provide one or more of the functionalities discussed herein. Furthermore, while “electronic” networks are generically used to refer to the communications network connecting the processing sites of the present invention, one skilled in the art would recognize that such networks could be implemented using optical or other equivalent technologies. Likewise, it is also to be understood that the present invention utilizes known security measures for transmission of electronic data across networks. Therefore, encryption, authentication, verification, and other security measures for transmission of electronic data across both public and private networks are provided, where necessary, using techniques that are well known to those skilled in the art.
• Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification and the practice of the invention disclosed herein. It is intended that the specification be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

Claims (13)

1-96. (canceled)

97. An RFID reader, comprising:

a) a controller;

b) a transmitter for generating a transmitted RF signal operatively connected to said controller, said transmitter having an output;

c) a receiver for receiving a received RF signal operatively coupled to said controller, said receiver having an input;

d) a coupler operatively connected to said output of said transmitter and said input of said receiver;

e) at least one antenna for alternately radiating said transmitted RF signal and receiving said received RF signal operatively connected to said coupler;

f) means for sensing a loading condition of said at least one antenna and producing an output indicative of said loading condition; and

g) means for selectively altering tuning of said at least one antenna operatively connected thereto and responsive to said output of said means for sensing.

98. The RFID reader as recited inclaim 97, wherein at least one of said means for sensing and said means for selectively altering tuning is operatively connected to said controller.

99. The RFID reader as recited inclaim 98, wherein at least one antenna comprises an array of antennas.

100. The RFID reader as recited inclaim 99, further comprising:

h) an antenna switch operatively connected to said controller, said coupler, and said array of antennas for selecting at least one antenna from said array of antennas and electrically connecting said selected at least one antenna to said coupler responsive to a command from said controller.

101. The RFID reader as recited inclaim 100, wherein said array of antenna are disposed on at least one of the group: shelf, and other merchandise display fixture and said RFID reader forms part of a smart shelf system.

102. The RFID reader as recited inclaim 100, wherein said means for altering antenna tuning comprises at least one from the group: a switched capacitor bank and a switched varactor bank.

103. The RFID reader as recited inclaim 102, wherein said switched capacitor bank and said switched varactor bank are switched in response to a command from said controller.

104. The RFID reader as recited inclaim 103, wherein altering antenna tuning comprises a tuning operation and said tuning operation is performed periodically.

105. The RFID reader as recited inclaim 103, wherein altering antenna tuning comprises a tuning operation and said tuning operation is performed responsive to a sensed change in tuning of at least one of said array of antennas.

106. The RFID reader as recited inclaim 97, wherein said transmitter further comprises a modulator and said transmitted signal may switched between a continuous wave (CW) RF signal and a selectively modulated RF signal upon commanded from said controller.

107. The RFID reader as recited inclaim 106, wherein said selectively modulated RF signal comprises an amplitude modulated (AM) RF signal.

108. The RFID reader as recited inclaim 97, further comprising means for arbitrating a data collision.

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