RFID TUNNEL READER
FIELD
The present invention relates to a tunnel reader for radio frequency identification (RFID) tags.
BACKGROUND
Radio frequency identification (RFID) tags are affixed to items for identification purposes. The tags comprise electric circuits and/or conductive tracks printed on the items themselves or on labels that can be affixed to the items. Passive RFID tags include no active circuit components, and when excited by electromagnetic radiation at a predetermined frequency respond with an excitation signal that includes a characteristic identification code of the tag. High frequency (HF) tags are produced by a number of suppliers, such as Tagsys. One of the applications of RFID technology is tracking and identifying blood products, such as blood bags, vials and specimens, using RFID tags. For example, the International Journal of Blood Transfusion Medicine has recently published guidelines for the use of RFID technology in transfusion medicine.
HF RFID tunnel readers are used to detect tags on items as the items are moved through a tunnel or path defined by the reader. One of the difficulties associated with reading identification codes from tags on blood products is that the products are normally required to be kept in a freezing environment, in temperatures as low as - 40°C.
It is desired to be able to provide a tunnel reader, or at least a useful alternative, that is capable of reading tags with a relatively high degree of accuracy as they move through the reader at temperatures as low as -40°C. Ideally such a reader should also be capable of reading HF Mode 1 and Mode 3 RFID tags.
SUMMARY
According to one aspect of the present invention there is provided a tunnel reader, including :
a frame defining an entry end and an exit end; and
radio frequency antennas in the frame tuned to resonate at a predetermined frequency and generate signals to interrogate HF RFID tags on items in a freezing environment moved in the reader from the entry end to the exit end.
The antennas may be dynamically tuned.
The antennas may be opposing pairs and the signals shifted in phase relative to one another so as to cause constructive interference of the interrogation signals.
At least one antenna may be active and at least one antenna may be parasitic and excited by the signals generated by the at least one active antenna.
The items may be blood products, such as blood bags, vials and specimens. The products may be read in a freezing environment. The environment may have a temperature as low as -40°C. The items may be placed in cooler containers as they move through the reader, and the cooler containers may include at least one parasitic antenna.
The antennas may be formed in a loop. The antennas may generate an elliptic radio frequency excitation field. The antennas may each comprise a loop that is substantially circular.
According to another aspect of the present invention there is provided a tunnel reader, including :
a frame defining an entry end and an exit end; and
radio frequency antennas in the frame tuned to resonate at a predetermined frequency and generate signals to interrogate HF RFID tags on blood products moved in the reader from the entry end to the exit end.
According to another aspect of the present invention there is provided a tunnel reader, including :
a frame defining an entry end and an exit end; and
radio frequency antennas tuned to resonate at a predetermined frequency and generate signals to interrogate HF RFID tags on items moved in the reader from the entry end to the exit end; and
wherein the antennas include opposing pairs and the signals driving the pairs are shifted in phase relative to one another so as to cause constructive interference of the interrogation signals.
DRAWINGS
Preferred embodiments of the present invention are hereinafter described, by way of example, with reference to the accompanying drawings, wherein :
Figure 1 is a perspective view of an embodiment of a tunnel reader;
Figure 2 is a schematic diagram of the tunnel reader showing a fi rst arrangement of antennas of the reader;
Figure 3 is a diagram illustrating interrogation signals generated by the reader;
Figure 4 is a schematic diagram of an alternative antenna arrangement for the reader;
Figure 5 is a perspective view of a further embodiment of the tunnel reader;
Figure 6 is a schematic view of the antennas of the further embodiment;
Figure 7 is a view of the electromagnetic field generated by one of the antennas; and
Figures 8 to 11 are schematic views of the further embodiment showing the possible axes of the radio frequency electromagnetic field in which an RFID tag may be energised or excited.
DESCRIPTION
A radio frequency identification (RFID) tunnel reader 100, as shown in Figure 1, comprises a frame 102 that has a cube shape, a rectangular prism shape (i.e. a cuboid) or similar shape. All sides of the frame 102 of the reader may be open, including the top 104 and the bottom 106. For the reader 100 shown in Figure 1, the top 104 and the bottom 106 are closed and so are the two opposing sides 108 and 110, so that the frame 102 has top, bottom and side walls. The only sides of the frame 102 that remain open are the two remaining opposing ends 112 and 114 which define entry and exit ends 112 and 114 for items that are passed through the reader 100. The ends 112 and 114 define entry and exit points of a tunnel of the reader 100 for the items. The frame 102 and any closed walls 108 and 110 and top or bottom 104 and 106 may be constructed of plastic material. By closing and opening different walls of the frame 102, different entry and exit ends are defined. For example, the first end 112 and the left side 108 may be open to define the entry and exit ends. Alternatively, only the top 104 may be open so that the entry and exit ends are the same with items lowered into the tunnel reader 100 to be read, and then lifted out of the top 104. For this embodiment all of the electronics circuits for the reader 100 can be placed on or embedded in the bottom 106.
Within the frame 102 of the reader 100 is included at least one RFID antenna 202, 204, 206, 208, 210 and 212. The RFID antennas 202 to 212 each include conductive loops of copper or coaxial cable connected to a tuning circuit 220. The tuning circuit 220 includes capacitors and resistors to tune the antenna to a resonant frequency depending on the items to be read. The tuning circuit 220 of an antenna 202 to 212 may be placed in any convenient location such that it is electrically connected to its respective conductive loop. The resonant frequency includes a frequency band centred on a predetermined high frequency (HF) in the MHz range. For example, the antennas 202 to 212 operate at a resonant frequency of 13.56MHz ± 7kHz. The six antennas generate RFID interrogation signals at the resonant frequency when triggered and powered by a RFID reader circuit (not shown) connected to each of the antennas. The RFID reader circuit includes a channel multiplexer module that enables it to cycle through each antenna so as to excite one antenna at a time while the remaining act as parasitic antennas. The electromagnetic fields of the interrogation signals generated by the antennas are represented by the concentric circles shown in Figure 3. The conductive loops of the antennas shown in Figure 2 follow the perimeters of each of the frame 102 and are effectively square in shape for a cube shape reader 100. For example, one antenna 212 follows the perimeter of the top 104, a second antenna 204 follows the perimeter of the bottom 106, a third antenna 210 follows the perimeter of the side 108, a fourth antenna 202 follows the perimeter of the other side 110, a fifth antenna 206 follows the first end 112 and a sixth antenna 208 follows the perimeter of the second end 114. A cube shaped reader 100 is about 500 mm2.
By arranging the antennas 202 to 212 in opposing pairs, e.g. directly opposite one another, the signals provided by the RFID reader circuit to drive each of pairs can be shifted in phase relative to one another so as to cause constructive interference of the interrogation signals produced by the pairs.
The reader 100 is able to accurately read RFID tags of items moved through the ends 112 and 114 so as to pass through the tunnel of the reader 100. The reader 100 is able to read Mode 1 and Mode 3 HF RFID tags, as defined by the ISO 18000 Standard . The antennas 202 to 212 receive the backscattered response signals from the excited tags and pass them to the connected RFID reader circuit for decoding. In particular, the reader 100 is able to read standard passive HF RFID tags when placed on or incorporated into blood products, such as blood bags, vials and specimens. The blood products may be placed in a cooler container, such as a Coleman Esky, and passed through the tunnel of the reader 100. The environment in which the reader 100 operates may be freezing, and at temperatures as lows as -40°C. The passive HF RFID tags may be of similar size to a credit card and have anti -collision capabilities so that multiple tags can be read at once.
Blood products collected at a blood donation centre can be placed in a cooler container and read by the tunnel reader 100 when exiting the premises. Blood bags and cooler containers or cool boxes can be read at a blood processing centre by the tunnel reader 100, again when entering and exiting premises. At a blood bank, the blood items in cool boxes can be read by the tunnel reader when exiting and entering, and similarly for a hospital, blood bags in cool boxes can be read by the tunnel reader when entering and exiting the premises before being distributed to patients.
In other embodiments of the tunnel reader 450, as shown in Figure 4, the antennas 400 and 402 can be arranged differently so as to be diagonal, such that the upper part of one loop of an antenna 400 is adjacent to the top of one end 112, whereas the bottom of the loop of the antenna 400 is across the bottom of the opposing end 114. An opposing antenna 402 that can constructively interfere with the first diagonal antenna 400 can then be placed so that the upper end of the loop of the antenna 400 is at the top of second end 114 and the bottom of the loop is at the bottom of the first end 112.
The RFID antennas used in the readers 100 and 450 may also be dynamically and digitally tuned so they can be adjusted depending on the tagged items to be read . This dynamic and digital tuning would involve automatically adjusting the resonant frequencies of the antennas as required.
Another embodiment of the tunnel reader 500, as shown in Figures 5 and 6, has a larger frame 502 so that whilst the entry end 112 and exit end 114 are the same size, the distance between a side 504 of the tunnel and the corners 506 of the frame 502 are greater so as to accommodate antennas 510, that are formed as loops instead of quadrilaterals. The loops 510 can be circular or elliptical.
The reader 500 includes eight antenna loops 510, 512, 514, 516, 518, 520, 522 and 524 disposed within the frame 502. As shown in Figure 6, four loops 510, 512, 514 and 516 are respectively coplanar with the side walls of the frame. One loop 518 is coplanar with the top of the frame, another loop 520 is coplanar with the bottom of the frame and two loops 522 and 524 extend diagonally across, over and under the tunnel defined by the ends 112 and 114. The interrogation signals generated by each loop 510 to 524 provides an elliptical or toroidal excitation electromagnetic field, as shown in Figure 7.
Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention.