US20100053023A1 - Antenna Array - Google Patents

Abstract

A circuit board for wireless communications includes communication circuitry for modulating and/or demodulating a radio frequency (RF) signal and an antenna apparatus for transmitting and receiving the RF signal, the antenna apparatus having selectable antenna elements located near one or more peripheries of the circuit board. A first antenna element produces a first directional radiation pattern; a second antenna element produces a second directional radiation pattern offset from the first radiation pattern. The antenna elements may include one or more reflectors configured to provide gain and broaden the frequency response of the antenna element. A switching network couples one or more of the selectable elements to the communication circuitry and provides impedance matching regardless of which or how many of the antenna elements are selected. Selecting different combinations of antenna elements results in a configurable radiation pattern; alternatively, selecting several elements may result in an omnidirectional radiation pattern.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• The present application is a continuation and claims the priority benefit of U.S. patent application Ser. No. 11/714,707 filed Mar. 5, 2007 and now U.S. Pat. No. 7,525,486, which is a continuation and claims the priority benefit of U.S. patent application Ser. No. 11/022,080 filed Dec. 23, 2004 and now U.S. Pat. No. 7,193,562, which claims the priority benefit of U.S. provisional patent application No. 60/630,499 filed Nov. 22, 2004. The disclosure of each of these applications is incorporated herein by reference.
• The present application is related to U.S. patent application Ser. No. 11/010,076 filed Dec. 9, 2004, which is also incorporated herein by reference.
BACKGROUND
• 1. Field of the Invention
• The present invention relates generally to wireless communications, and more particularly to a circuit board having a peripheral antenna apparatus with selectable antenna elements.
• 2. Description of the Related Art
• In communications systems, there is an ever-increasing demand for higher data throughput and a corresponding drive to reduce interference that can disrupt data communications. For example, in an IEEE 802.11 network, an access point (i.e., base station) communicates data with one or more remote receiving nodes (e.g., a network interface card) over a wireless link. The wireless link may be susceptible to interference from other access points, other radio transmitting devices, changes or disturbances in the wireless link environment between the access point and the remote receiving node, and so on. The interference may be such to degrade the wireless link, for example by forcing communication at a lower data rate, or may be sufficiently strong to completely disrupt the wireless link.
• One solution for reducing interference in the wireless link between the access point and the remote receiving node is to provide several omnidirectional antennas for the access point, in a “diversity” scheme. For example, a common configuration for the access point comprises a data source coupled via a switching network to two or more physically separated omnidirectional antennas. The access point may select one of the omnidirectional antennas by which to maintain the wireless link. Because of the separation between the omnidirectional antennas, each antenna experiences a different signal environment, and each antenna contributes a different interference level to the wireless link. The switching network couples the data source to whichever of the omnidirectional antennas experiences the least interference in the wireless link.
• However, one limitation with using two or more omnidirectional antennas for the access point is that each omnidirectional antenna comprises a separate unit of manufacture with respect to the access point, thus requiring extra manufacturing steps to include the omnidirectional antennas in the access point. A further limitation is that the omnidirectional antenna typically comprises an upright wand attached to a housing of the access point. The wand typically comprises a rod exposed outside of the housing, and may be subject to breakage or damage.
• Another limitation is that typical omnidirectional antennas are vertically polarized. Vertically polarized radio frequency (RF) energy does not travel as efficiently as horizontally polarized RF energy inside a typical office or dwelling space, additionally, most laptop computer network interface cards have horizontally polarized antennas. Typical solutions for creating horizontally polarized RF antennas to date have been expensive to manufacture, or do not provide adequate RF performance to be commercially successful.
• A still further limitation with the two or more omnidirectional antennas is that because the physically separated antennas may still be relatively close to each other, each of the several antennas may experience similar levels of interference and only a relatively small reduction in interference may be gained by switching from one omnidirectional antenna to another omnidirectional antenna.
SUMMARY
• An exemplary embodiment of the present invention includes an antenna array.
BRIEF DESCRIPTION OF THE DRAWINGS
• The present invention will now be described with reference to drawings that represent a preferred embodiment of the invention. In the drawings, like components have the same reference numerals. The illustrated embodiment is intended to illustrate, but not to limit the invention. The drawings include the following figures:
• FIG. 1 illustrates an exemplary schematic for a system incorporating a circuit board having a peripheral antenna apparatus with selectable elements, in one embodiment in accordance with the present invention;
• FIG. 2 illustrates the circuit board having the peripheral antenna apparatus with selectable elements ofFIG. 1, in one embodiment in accordance with the present invention;
• FIG. 3A illustrates a modified dipole for the antenna apparatus ofFIG. 2, in one embodiment in accordance with the present invention;
• FIG. 3B illustrates a size reduced modified dipole for the antenna apparatus ofFIG. 2, in an alternative embodiment in accordance with the present invention;
• FIG. 3C illustrates an alternative modified dipole for the antenna apparatus ofFIG. 2, in an alternative embodiment in accordance with the present invention;
• FIG. 3D illustrates a modified dipole with coplanar strip transition for the antenna apparatus ofFIG. 2, in an alternative embodiment in accordance with the present invention;
• FIG. 4 illustrates the antenna element ofFIG. 3A, showing multiple layers of the circuit board, in one embodiment of the invention;
• FIG. 5A illustrates the antenna feed port and the switching network ofFIG. 2, in one embodiment in accordance with the present invention;
• FIG. 5B illustrates the antenna feed port and the switching network ofFIG. 2, in an alternative embodiment in accordance with the present invention; and
• FIG. 5C illustrates the antenna feed port and the switching network ofFIG. 2, in an alternative embodiment in accordance with the present invention.
DETAILED DESCRIPTION
• A system for a wireless (i.e., radio frequency or RF) link to a remote receiving device includes a circuit board comprising communication circuitry for generating an RF signal and an antenna apparatus for transmitting and/or receiving the RF signal. The antenna apparatus includes two or more antenna elements arranged near the periphery of the circuit board. Each of the antenna elements provides a directional radiation pattern. In some embodiments, the antenna elements may be electrically selected (e.g., switched on or off) so that the antenna apparatus may form configurable radiation patterns. If multiple antenna elements are switched on, the antenna apparatus may form an omnidirectional radiation pattern.
• Advantageously, the circuit board interconnects the communication circuitry and provides the antenna apparatus in one easily manufacturable printed circuit board. Including the antenna apparatus in the printed circuit board reduces the cost to manufacture the circuit board and simplifies interconnection with the communication circuitry. Further, including the antenna apparatus in the circuit board provides more consistent RF matching between the communication circuitry and the antenna elements. A further advantage is that the antenna apparatus radiates directional radiation patterns substantially in the plane of the antenna elements. When mounted horizontally, the radiation patterns are horizontally polarized, so that RF signal transmission indoors is enhanced as compared to a vertically polarized antenna.
• FIG. 1 illustrates an exemplary schematic for asystem100 incorporating a circuit board having a peripheral antenna apparatus with selectable elements, in one embodiment in accordance with the present invention. Thesystem100 may comprise, for example without limitation, a transmitter/receiver such as an 802.11 access point, an 802.11 receiver, a set-top box, a laptop computer, a television, a cellular telephone, a cordless telephone, a wireless VoIP phone, a remote control, and a remote terminal such as a handheld gaming device. In some exemplary embodiments, thesystem100 comprises an access point for communicating to one or more remote receiving nodes over a wireless link, for example in an 802.11 wireless network.
• Thesystem100 comprises acircuit board105 including a radio modulator/demodulator (modem)120 and aperipheral antenna apparatus110. Theradio modem120 may receive data from a router connected to the Internet (not shown), convert the data into a modulated RF signal, and theantenna apparatus110 may transmit the modulated RF signal wirelessly to one or more remote receiving nodes (not shown). Thesystem100 may also form a part of a wireless local area network by enabling communications among several remote receiving nodes. Although the disclosure will focus on a specific embodiment for thesystem100 including thecircuit board105, aspects of the invention are applicable to a wide variety of appliances, and are not intended to be limited to the disclosed embodiment. For example, although thesystem100 may be described as transmitting to a remote receiving node via theantenna apparatus110, thesystem100 may also receive RF-modulated data from the remote receiving node via theantenna apparatus110.
• FIG. 2 illustrates thecircuit board105 having theperipheral antenna apparatus110 with selectable elements ofFIG. 1, in one embodiment in accordance with the present invention. In some embodiments, thecircuit board105 comprises a printed circuit board (PCB) such as FR4, Rogers 4003, or other dielectric material with four layers, although any number of layers is comprehended, such as six.
• Thecircuit board105 includes anarea210 for interconnecting circuitry including for example apower supply215, anantenna selector220, adata processor225, and a radio modulator/demodulator (modem)230. In some embodiments, thedata processor225 comprises well-known circuitry for receiving data packets from a router connected to the Internet (e.g., via a local area network). Theradio modem230 comprises communication circuitry including virtually any device for converting the data packets processed by thedata processor225 into a modulated RF signal for transmission to one or more of the remote receiving nodes, and for reception therefrom. In some embodiments, theradio modem230 comprises circuitry for converting the data packets into an 802.11 compliant modulated RF signal.
• From theradio modem230, thecircuit board105 also includes amicrostrip RF line234 for routing the modulated RF signal to anantenna feed port235. Although not shown, in some embodiments, anantenna feed port235 is configured to distribute the modulated RF signal directly toantenna elements240A-240G of the peripheral antenna apparatus110 (not labeled) by way of antenna feed lines. In the embodiment depicted inFIG. 2, theantenna feed port235 is configured to distribute the modulated RF signal to one or more of theselectable antenna elements240A-240G by way of aswitching network237 andmicrostrip feed lines239A-239G. Although described as microstrip, the feed lines239 may also comprise coupled microstrip, coplanar strips with impedance transformers, coplanar waveguide, coupled strips, and the like.
• Theantenna feed port235, theswitching network237, and the feed lines239 comprise switching and routing components on thecircuit board105 for routing the modulated RF signal to theantenna elements240A-240G. As described further herein, theantenna feed port235, theswitching network237, and the feed lines239 include structures for impedance matching between theradio modem230 and the antenna elements240. Theantenna feed port235, theswitching network237, and the feed lines239 are further described with respect toFIG. 5.
• As described further herein, the peripheral antenna apparatus comprises a plurality ofantenna elements240A-240G located near peripheral areas of thecircuit board105. Each of the antenna elements240 produces a directional radiation pattern with gain (as compared to an omnidirectional antenna) and with polarization substantially in the plane of thecircuit board105. Each of the antenna elements may be arranged in an offset direction from the other antenna elements240 so that the directional radiation pattern produced by one antenna element (e.g., theantenna element240A) is offset in direction from the directional radiation pattern produced by another antenna element (e.g., theantenna element240C). Certain antenna elements may also be arranged in substantially the same direction, such as theantenna elements240D and240E. Arranging two or more of the antenna elements240 in the same direction provides spatial diversity between the antenna elements240 so arranged.
• In embodiments with theswitching network237, selecting various combinations of the antenna elements240 produces various radiation patterns ranging from highly directional to omnidirectional. Generally, enabling adjacent antenna elements240 results in higher directionality in azimuth as compared to selecting either of the antenna elements240 alone. For example, selecting theadjacent antenna elements240A and240B may provide higher directionality than selecting either of theantenna elements240A or240B alone. Alternatively, selecting every other antenna element (e.g., theantenna elements240A,240C,240E, and240G) or all of the antenna elements240 may produce an omnidirectional radiation pattern.
• The operating principle of the selectable antenna elements240 may be further understood by review of co-pending U.S. patent application Ser. No. 11/010,076, entitled “System and Method for an Omnidirectional Planar Antenna Apparatus with Selectable Elements,” filed Dec. 9, 2004, and previously incorporated herein by reference.
• FIG. 3A illustrates theantenna element240A ofFIG. 2, in one embodiment in accordance with the present invention. Theantenna element240A of this embodiment comprises a modified dipole with components on both exterior surfaces of the circuit board105 (considered as the plane ofFIG. 3A). Specifically, on a first surface of thecircuit board105, theantenna element240A includes afirst dipole component310. On a second surface of thecircuit board105, depicted by dashed lines inFIG. 3, theantenna element240A includes asecond dipole component311 extending substantially opposite from thefirst dipole component310. Thefirst dipole component310 and thesecond dipole component311 form theantenna element240A to produce a generally cardioid directional radiation pattern substantially in the plane of the circuit board.
• In some embodiments, such as theantenna elements240B and240C ofFIG. 2, thedipole component310 and/or thedipole component311 may be bent to conform to an edge of thecircuit board105. Incorporating the bend in thedipole component310 and/or thedipole component311 may reduce the size of thecircuit board105. Although described as being formed on the surface of thecircuit board105, in some embodiments thedipole components310 and311 are formed on interior layers of the circuit board, as described herein.
• Theantenna element240A may optionally include one or more reflectors (e.g., the reflector312). Thereflector312 comprises elements that may be configured to concentrate the directional radiation pattern formed by thefirst dipole component310 and thesecond dipole component311. Thereflector312 may also be configured to broaden the frequency response of theantenna component240A. In some embodiments, thereflector312 broadens the frequency response of each modified dipole to about 300 MHz to 500 MHz. In some embodiments, the combined operational bandwidth of the antenna apparatus resulting from coupling more than one of the antenna elements240 to theantenna feed port235 is less than the bandwidth resulting from coupling only one of the antenna elements240 to theantenna feed port235. For example, with four antenna elements240 (e.g., theantenna elements240A,240C,240E, and240G) selected to result in an omnidirectional radiation pattern, the combined frequency response of the antenna apparatus is about 90 MHz. In some embodiments, coupling more than one of the antenna elements240 to theantenna feed port235 maintains a match with less than 10 dB return loss over 802.11 wireless LAN frequencies, regardless of the number of antenna elements240 that are switched on.
• FIG. 3B illustrates theantenna element240A ofFIG. 2, in an alternative embodiment in accordance with the present invention. Theantenna element240A of this embodiment may be reduced in dimension as compared to theantenna element240A ofFIG. 3A. Specifically, theantenna element240A of this embodiment comprises afirst dipole component315 incorporating a meander, asecond dipole component316 incorporating a corresponding meander, and areflector317. Because of the meander, theantenna element240A of this embodiment may require less space on thecircuit board105 as compared to theantenna element240A ofFIG. 3A.
• FIG. 3C illustrates theantenna element240A ofFIG. 2, in an alternative embodiment in accordance with the present invention. Theantenna element240A of this embodiment includes one or more components on one or more layers internal to thecircuit board105. Specifically, in one embodiment, afirst dipole component321 is formed on an internal ground plane of thecircuit board105. Asecond dipole component322 is formed on an exterior surface of thecircuit board105. As described further with respect toFIG. 4, areflector323 may be formed internal to thecircuit board105, or may be formed on the exterior surface of thecircuit board105. An advantage of this embodiment of theantenna element240A is that vias through thecircuit board105 may be reduced or eliminated, making theantenna element240A of this embodiment less expensive to manufacture.
• FIG. 3D illustrates theantenna element240A ofFIG. 2, in an alternative embodiment in accordance with the present invention. Theantenna element240A of this embodiment includes a modified dipole with a microstrip to coplanar strip (CPS)transition332 andCPS dipole arms330A and330B on a surface layer of thecircuit board105. Specifically, this embodiment provides that theCPS dipole arm330A may be coplanar with theCPS dipole arm330B, and may be formed on the same surface of thecircuit board105. This embodiment may also include areflector331 formed on one or more interior layers of thecircuit board105 or on the opposite surface of thecircuit board105. An advantage of this embodiment is that no vias are needed in thecircuit board105.
• It will be appreciated that the dimensions of the individual components of theantenna elements240A-G (e.g., thefirst dipole component310, thesecond dipole component311, and the reflector312) depend upon a desired operating frequency of the antenna apparatus. Furthermore, it will be appreciated that the dimensions of wavelength depend upon conductive and dielectric materials comprising thecircuit board105, because speed of electron propagation depends upon the properties of thecircuit board105 material. Therefore, dimensions of wavelength referred to herein are intended specifically to incorporate properties of the circuit board, including considerations such as the conductive and dielectric properties of thecircuit board105. The dimensions of the individual components may be established by use of RF simulation software, such as IE3D from Zeland Software of Fremont, Calif.
• FIG. 4 illustrates theantenna element240A ofFIG. 3A, showing multiple layers of thecircuit board105, in one embodiment of the invention. Thecircuit board105 of this embodiment comprises a 60 mil thick stackup with three dielectrics and four metallization layers A-D, with an internal RF ground plane at layer B (10 mils from top layer A to the internal ground layer B). Layer B is separated by a 40 mil thick dielectric to the next layer C, which may comprise a power plane. Layer C is separated by a 10 mil dielectric to the bottom layer D.
• Thefirst dipole component310 andportions412A of thereflector312 is formed on the first (exterior) surface layer A. In the second metallization layer B, which includes a connection to the ground layer (depicted as an open trace), correspondingportions412B of thereflector312 are formed. On the third metallization layer C, correspondingportions412C of thereflector312 are formed. Thesecond dipole component411D is formed along with corresponding portions of thereflector412D on the fourth (exterior) surface metallization layer D. Thereflectors412A-D and the second dipole component411B-D on the different layers are interconnected to the ground layer B by an array of metallized vias415 (only one via415 shown, for clarity) spaced less than 1/20th of a wavelength apart, as determined by an operating RF frequency range of 2.4-2.5 GHz for 802.11. It will be apparent to a person or ordinary skill that thereflector312 comprises four layers, depicted as412A-D.
• An advantage of theantenna element240A ofFIG. 4 is that transitions in the RF path are avoided. Further, because of the cutaway portion of thereflector412A and the array of vias interconnecting the layers of thecircuit board105, theantenna element240A of this embodiment offers a good ground plane for theground dipole311 and thereflector element312.
• FIG. 5A illustrates theantenna feed port235 and theswitching network237 ofFIG. 2, in one embodiment in accordance with the present invention. Theantenna feed port235 of this embodiment receives theRF line234 from theradio modem230 into adistribution point235A. From thedistribution point235A, impedance matched RF traces515A-G extend toPIN diodes520A-G. In one embodiment, the RF traces515A-G comprise 20 mils wide traces, based upon a 10 mil dielectric from the internal ground layer (e.g., the ground layer B ofFIG. 4).Feed lines239A-G (only portions of the feed lines239 are shown for clarity) extend from thePIN diodes520A-G to each of the antenna elements240.
• Each PIN diode520 comprises a single-pole single-throw switch to switch each antenna element240 either on or off (i.e., couple or decouple each of the antenna elements240 to the antenna feed port235). In one embodiment, a series of control signals (not shown) is used to bias each PIN diode520. With the PIN diode520 forward biased and conducting a DC current, the PIN diode520 is switched on, and the corresponding antenna element240 is selected. With the PIN diode520 reverse biased, the PIN diode520 is switched off.
• In one embodiment, the RF traces515A-G are of length equal to a multiple of one half wavelength from theantenna feed port235. Although depicted as equal length inFIG. 5A, the RF traces515A-G may be unequal in length, but multiples of one half wavelength from theantenna feed port235. For example, theRF trace515A may be of zero length so that thePIN diode520A is directly attached to theantenna feed port235. TheRF trace515B may be one half wavelength, theRF trace515C may be one wavelength, and so on, in any combination. ThePIN diodes520A-G are multiples of one half wavelength from theantenna feed port235 so that disabling one PIN diode (e.g. thePIN diode520A) does not create an RF mismatch that would cause RF reflections back to thedistribution point235A and to other traces515 that are enabled (e.g., thetrace515B). In this fashion, when the PIN diode540A is “off,” theradio modem230 sees a high impedance on thetrace515A, and the impedance of thetrace515B that is “on” is virtually unaffected by the PIN diode540A. In some embodiments, thePIN diodes520A-G are located at an offset from the one half wavelength distance. The offset is determined to account for stray capacitance in thedistribution point235A and/or thePIN diodes520A-G.
• FIG. 5B illustrates theantenna feed port235 and theswitching network237 ofFIG. 2, in an alternative embodiment in accordance with the present invention. Theantenna feed port235 of this embodiment receives theRF line234 from theradio modem230 into adistribution point235B. Thedistribution point235B of this embodiment is configured as a solder pad for thePIN diodes520A-G. ThePIN diodes520A-G are soldered between thedistribution point235B and the ends of thefeed lines239A-G. In essence, thedistribution point235B of this embodiment acts as a zero wavelength distance from theantenna feed port235. An advantage of this embodiment is that the feed lines extending from thePIN diodes520A-G to theantenna elements240A-G offer unbroken controlled impedance.
• FIG. 5C illustrates the antenna feed port and the switching network ofFIG. 2, in an alternative embodiment in accordance with the present invention. This embodiment may be considered as a combination of the embodiments depicted inFIGS. 5A and 5B. ThePIN diodes520A,520C,520E, and520G are connected to the RF traces515A,515C,515E, and515G, respectively, in similar fashion to that described with respect toFIG. 5A. However, thePIN diodes520B,520D, and520F are soldered to adistribution point235C and to thecorresponding feed lines239B,239D, and239F, in similar fashion to that described with respect toFIG. 5B.
• Although theswitching network237 is described as comprising PIN diodes520, it will be appreciated that theswitching network237 may comprise virtually any RF switching device such as a GaAs FET, as is well known in the art. In some embodiments, theswitching network237 comprises one or more single-pole multiple-throw switches. In some embodiments, one or more light emitting diodes (not shown) are coupled to theswitching network237 or the feed lines239 as a visual indicator of which of the antenna elements240 is on or off. In one embodiment, a light emitting diode is placed in circuit with each PIN diode520 so that the light emitting diode is lit when the corresponding antenna element240 is selected.
• Referring toFIG. 2, because in some embodiments theantenna feed port235 is not in the center of thecircuit board105, which would make the antenna feed lines239 of equal length and minimum loss, the lengths of the antenna feed lines239 may not comprise equivalent lengths from theantenna feed port235. Unequal lengths of the antenna feed lines239 may result in phase offsets between the antenna elements240. Accordingly, in some embodiments not shown inFIG. 2, each of the feed lines239 to the antenna elements240 are designed to be as long as the longest of the feed lines239, even for antenna elements240 that are relatively close to theantenna feed port235. In some embodiments, the lengths of the feed lines239 are designed to be a multiple of a half-wavelength offset from the longest of the feed lines239. In still other embodiments, the lengths of the feed lines239 which are odd multiples of one half wavelength from the other feed lines239 incorporate a “phase-inverted” antenna element240 to compensate. For example, referring toFIG. 2, theantenna elements240C and240F are inverted by 180 degrees because thefeed lines239C and239F are 180 degrees out of phase from thefeed lines239A,239B,239D,239E, and239G. In an antenna element240 that is phase inverted, the first dipole component (e.g., surface layer) replaces the second dipole component (e.g., ground layer). It will be appreciated that this provides the 180 degree phase shift in the antenna element to compensate for the 180 degree feed line phase shift.
• An advantage of the system100 (FIG. 1) incorporating thecircuit board105 having the peripheral antenna apparatus with selectable antenna elements240 (FIG. 2) is that the antenna elements240 are constructed directly on thecircuit board105, therefore theentire circuit board105 can be easily manufactured at low cost. As depicted inFIG. 2, one embodiment or layout of thecircuit board105 comprises a substantially square or rectangular shape, so that thecircuit board105 is easily panelized from readily available circuit board material. As compared to a system incorporating externally-mounted vertically polarized “whip” antennas for diversity, thecircuit board105 minimizes or eliminates the possibility of damage to the antenna elements240.
• A further advantage of thecircuit board105 incorporating the peripheral antenna apparatus with selectable antenna elements240 is that the antenna elements240 may be configured to reduce interference in the wireless link between thesystem100 and a remote receiving node. For example, thesystem100 communicating over the wireless link to the remote receiving node may select a particular configuration of selected antenna elements240 that minimizes interference over the wireless link. For example, if an interfering signal is received strongly via theantenna element240C, and the remote receiving node is received strongly via theantenna element240A, selecting only theantenna element240A may reduce the interfering signal as opposed to selecting theantenna element240C. Thesystem100 may select a configuration of selected antenna elements240 corresponding to a maximum gain between the system and the remote receiving node. Alternatively, thesystem100 may select a configuration of selected antenna elements240 corresponding to less than maximal gain, but corresponding to reduced interference. Alternatively, the antenna elements240 may be selected to form a combined omnidirectional radiation pattern.
• Another advantage of thecircuit board105 is that the directional radiation pattern of the antenna elements240 is substantially in the plane of thecircuit board105. When thecircuit board105 is mounted horizontally, the corresponding radiation patterns of the antenna elements240 are horizontally polarized. Horizontally polarized RF energy tends to propagate better indoors than vertically polarized RF energy. Providing horizontally polarized signals improves interference rejection (potentially, up to 20 dB) from RF sources that use commonly-available vertically polarized antennas.
• The invention has been described herein in terms of several preferred embodiments. Other embodiments of the invention, including alternatives, modifications, permutations and equivalents of the embodiments described herein, will be apparent to those skilled in the art from consideration of the specification, study of the drawings, and practice of the invention. The embodiments and preferred features described above should be considered exemplary, with the invention being defined by the appended claims, which therefore include all such alternatives, modifications, permutations and equivalents as fall within the true spirit and scope of the present invention.

Claims (1)

1. An antenna array for increasing wireless coverage, comprising:

a radio frequency (RF) signal modulator configured to generate a modulated RF signal;

a plurality of modulated RF signal emission points arranged in a substantially circular pattern around the periphery of the antenna array; and

a switching network configured to control a modulated RF signal radiation pattern emitted by each of the plurality of modulated RF signal emission points, wherein each of the plurality of modulated RF signal emission points emits a directional radiation pattern offset from the directional radiation pattern of each of the other modulated RF signal emission points, the directional radiation patterns emitted by the plurality of modulated RF signal emission points collectively generating a substantially 360-degree coverage pattern.

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