Patent Publication Number: US-9837711-B2

Title: Antenna with selectable elements for use in wireless communications

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional and claims the priority benefit of U.S. patent application Ser. No. 11/877,465 filed Oct. 23, 2007 and entitled “Antenna with Selectable Elements for Use in Wireless Communications,” which is a continuation and claims the priority benefit of U.S. patent application Ser. No. 11/010,076 filed Dec. 9, 2004 and entitled “System and Method for an Omnidirectional Planar Antenna Apparatus with Selectable Elements,” which is now U.S. Pat. No. 7,292,198, which claims the priority benefit of U.S. Provisional Application No. 60/602,711 entitled “Planar Antenna Apparatus for Isotropic Coverage and QoS Optimization in Wireless Networks,” filed Aug. 18, 2004, and U.S. Provisional Application No. 60/603,157 entitled “Software for Controlling a Planar Antenna Apparatus for Isotropic Coverage and QoS Optimization in Wireless Networks,” filed Aug. 18, 2004. The disclosure of each of the aforementioned applications is incorporated by reference. 
    
    
     BACKGROUND OF INVENTION 
     Field of the Invention 
     The present invention relates generally to wireless communications networks, and more particularly to a system and method for an omnidirectional planar antenna apparatus with selectable elements. 
     Description of the Prior 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 problem with using two or more omnidirectional antennas for the access point 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 of the laptop computer wireless 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 further problem is that the omnidirectional antenna typically comprises an upright wand attached to a housing of the access point. The wand typically comprises a hollow metallic rod exposed outside of the housing, and may be subject to breakage or damage. Another problem 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 still further problem 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. 
     Another solution to reduce interference involves beam steering with an electronically controlled phased array antenna. However, the phased array antenna can be extremely expensive to manufacture. Further, the phased array antenna can require many phase tuning elements that may drift or otherwise become maladjusted. 
     SUMMARY OF INVENTION 
     In a first claimed embodiment, a network peripheral device is disclosed. The device includes a plurality of antennas and at least a single wireless module that is operable with the plurality of antennas. The single wireless module includes a single baseband operable with the plurality of antennas, an antenna selector control module operable with the baseband, and a processor. The device further includes a plurality of electronically controllable visual indicators and circuitry that activates and deactivates selected indicators from the plurality of indicators. The activation and deactivation corresponds to selection and deselection of respective antennas from among the plurality of antennas by the single wireless module as the single wireless module continues to operate. 
    
    
     
       BRIEF DESCRIPTION OF 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 a system comprising an omnidirectional planar antenna apparatus with selectable elements, in one embodiment in accordance with the present invention; 
         FIG. 2A  and  FIG. 2B  illustrate the planar antenna apparatus of  FIG. 1 , in one embodiment in accordance with the present invention; 
         FIGS. 2C and 2D  illustrate dimensions for several components of the planar antenna apparatus of  FIG. 1 , in one embodiment in accordance with the present invention; 
         FIG. 3A  illustrates various radiation patterns resulting from selecting different antenna elements of the planar antenna apparatus of  FIG. 2 , in one embodiment in accordance with the present invention; 
         FIG. 3B  illustrates an elevation radiation pattern for the planar antenna apparatus of  FIG. 2 , in one embodiment in accordance with the present invention; and 
         FIG. 4A  and  FIG. 4B  illustrate an alternative embodiment of the planar antenna apparatus  110  of  FIG. 1 , 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 communication device for generating an RF signal and a planar antenna apparatus for transmitting and/or receiving the RF signal. The planar antenna apparatus includes selectable antenna elements. Each of the antenna elements provides gain (with respect to isotropic) and a directional radiation pattern substantially in the plane of the antenna elements. Each antenna element may be electrically selected (e.g., switched on or off) so that the planar antenna apparatus may form a configurable radiation pattern. If all elements are switched on, the planar antenna apparatus forms an omnidirectional radiation pattern. In some embodiments, if two or more of the elements is switched on, the planar antenna apparatus may form a substantially omnidirectional radiation pattern. 
     Advantageously, the system may select a particular configuration of selected antenna elements that minimizes interference over the wireless link to the remote receiving device. If the wireless link experiences interference, for example due to other radio transmitting devices, or changes or disturbances in the wireless link between the system and the remote receiving device, the system may select a different configuration of selected antenna elements to change the resulting radiation pattern and minimize the interference. The system may select a configuration of selected antenna elements corresponding to a maximum gain between the system and the remote receiving device. Alternatively, the system may select a configuration of selected antenna elements corresponding to less than maximal gain, but corresponding to reduced interference in the wireless link. 
     As described further herein, the planar antenna apparatus radiates the directional radiation pattern substantially in the plane of the antenna elements. When mounted horizontally, the RF signal transmission is horizontally polarized, so that RF signal transmission indoors is enhanced as compared to a vertically polarized antenna. The planar antenna apparatus is easily manufactured from common planar substrates such as an FR4 printed circuit board (PCB). Further, the planar antenna apparatus may be integrated into or conformally mounted to a housing of the system, to minimize cost and to provide support for the planar antenna apparatus. 
       FIG. 1  illustrates a system  100  comprising an omnidirectional planar antenna apparatus with selectable elements, in one embodiment in accordance with the present invention. The system  100  may comprise, for example without limitation, a transmitter and/or a receiver, such as an 802.11 access point, an 802.11 receiver, a set-top box, a laptop computer, a television, a PCMCIA card, a remote control, and a remote terminal such as a handheld gaming device. In some exemplary embodiments, the system  100  comprises an access point  130  for communicating to one or more remote receiving nodes  140   a - 140   d  over a wireless link  150 , for example in an 802.11 wireless network. Typically, the system  100  may receive data from a router connected to the Internet (not shown), and the system  100  may transmit the data to one or more of the remote receiving nodes  140   a - 140   d . The system  100  may also from 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 the system  100 , 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 the system  100  may be described as transmitting to the remote receiving node via the planar antenna apparatus, the system  100  may also receive data from the remote receiving node via the planar antenna apparatus. 
     The system  100  includes a communication device  120  (e.g., a transceiver) and a planar antenna apparatus  110 . The communication device  120  comprises virtually any device for generating and/or receiving an RF signal. The communication device  120  may include, for example, a radio modulator/demodulator for converting data received into the system  100  (e.g., from the router) into the RF signal for transmission to one or more of the remote receiving nodes. In some embodiments, for example, the communication device  120  comprises well-known circuitry for receiving data packets of video from the router and circuitry for converting the data packets into 802.11 compliant RF signals. 
     As described further herein, the planar antenna apparatus  110  comprises a plurality of individually selectable planar antenna elements. Each of the antenna elements has a directional radiation pattern with gain (as compared to an omnidirectional antenna). Each of the antenna elements also has a polarization substantially in the plane of the planar antenna apparatus  110 . The planar antenna apparatus  110  may include an antenna element selecting device configured to selectively couple one or more of the antenna elements to the communication device  120 . 
       FIG. 2A  and  FIG. 2B  illustrate the planar antenna apparatus  110  of  FIG. 1 , in one embodiment in accordance with the present invention. The planar antenna apparatus  110  of this embodiment includes a substrate (considered as the plane of  FIGS. 2A and 2B ) having a first side (e.g.,  FIG. 2A ) and a second side (e.g.,  FIG. 2B ) substantially parallel to the first side. In some embodiments, the substrate comprises a PCB such as FR4, Rogers 4003, or other dielectric material. 
     On the first side of the substrate, the planar antenna apparatus  110  of  FIG. 2A  includes a radio frequency feed port  220  and four antenna elements  205   a - 205   d . As described with respect to  FIG. 4 , although four antenna elements are depicted, more or fewer antenna elements are contemplated. Although the antenna elements  205   a - 205   d  of  FIG. 2A  are oriented substantially on diagonals of a square shaped planar antenna so as to minimize the size of the planar antenna apparatus  110 , other shapes are contemplated. Further, although the antenna elements  205   a - 205   d  form a radially symmetrical layout about the radio frequency feed port  220 , a number of non-symmetrical layouts, rectangular layouts, and layouts symmetrical in only one axis, are contemplated. Furthermore, the antenna elements  205   a - 205   d  need not be of identical dimension, although depicted as such in  FIG. 2A . 
     On the second side of the substrate, as shown in  FIG. 2B , the planar antenna apparatus  110  includes a ground component  225 . It will be appreciated that a portion (e.g., the portion  230   a ) of the ground component  225  is configured to form an arrow-shaped bent dipole in conjunction with the antenna element  205   a . The resultant bent dipole provides a directional radiation pattern substantially in the plane of the planar antenna apparatus  110 , as described further with respect to  FIG. 3 . 
       FIGS. 2C and 2D  illustrate dimensions for several components of the planar antenna apparatus  110 , in one embodiment in accordance with the present invention. It will be appreciated that the dimensions of the individual components of the planar antenna apparatus  110  (e.g., the antenna element  205   a , the portion  230   a  of the ground component  205 ) depend upon a desired operating frequency of the planar antenna apparatus  110 . The dimensions of the individual components may be established by use of RF simulation software, such as IE3D from Zeland Software of Fremont, Calif. For example, the planar antenna apparatus  110  incorporating the components of dimension according to  FIGS. 2C and 2D  is designed for operation near 2.4 GHz, based on a substrate PCB of Rogers 4003 material, but it will be appreciated by an antenna designer of ordinary skill that a different substrate having different dielectric properties, such as FR4, may require different dimensions than those shown in  FIGS. 2C and 2D . 
     As shown in  FIG. 2 , the planar antenna apparatus  110  may optionally include one or more directors  210 , one or more gain directors  215 , and/or one or more Y-shaped reflectors  235  (e.g., the Y-shaped reflector  235   b  depicted in  FIGS. 2B and 2D ). The directors  210 , the gain directors  215 , and the Y-shaped reflectors  235  comprise passive elements that concentrate the directional radiation pattern of the dipoles formed by the antenna elements  205   a - 205   d  in conjunction with the portions  230   a - 230   d . In one embodiment, providing a director  210  for each antenna element  205   a - 205   d  yields an additional 1-2 dB of gain for each dipole. It will be appreciated that the directors  210  and/or the gain directors  215  may be placed on either side of the substrate. In some embodiments, the portion of the substrate for the directors  210  and/or gain directors  215  is scored so that the directors  210  and/or gain directors  215  may be removed. It will also be appreciated that additional directors (depicted in a position shown by dashed line  211  for the antenna element  205   b ) and/or additional gain directors (depicted in a position shown by a dashed line  216 ) may be included to further concentrate the directional radiation pattern of one or more of the dipoles. The Y-shaped reflectors  235  will be further described herein. 
     The radio frequency feed port  220  is configured to receive an RF signal from and/or transmit an RF signal to the communication device  120  of  FIG. 1 . An antenna element selector (not shown) may be used to couple the radio frequency feed port  220  to one or more of the antenna elements  205   a - 205   d . The antenna element selector may comprise an RF switch (not shown), such as a PIN diode, a GaAs FET, or virtually any RF switching device, as is well known in the art. 
     In the embodiment of  FIG. 2A , the antenna element selector comprises four PIN diodes  240   a - 240   d , each PIN diode  240   a - 240   d  connecting one of the antenna elements  205   a - 205   d  to the radio frequency feed port  220 . In this embodiment, the PIN diode comprises a single-pole single-throw switch to switch each antenna element either on or off (i.e., couple or decouple each of the antenna elements  205   a - 205   d  to the radio frequency feed port  220 ). In one embodiment, a series of control signals (not shown) is used to bias each PIN diode  240   a - 240   d . With the PIN diode forward biased and conducting a DC current, the PIN diode switch is on, and the corresponding antenna element is selected. With the diode reverse biased, the PIN diode switch is off. In this embodiment, the radio frequency feed port  220  and the PIN diodes  240   a - 240   d  of the antenna element selector are on the side of the substrate with the antenna elements  205   a - 205   d , however, other embodiments separate the radio frequency feed port  220 , the antenna element selector, and the antenna elements  205   a - 205   d . In some embodiments, the antenna element selector comprises one or more single-pole multiple-throw switches. In some embodiments, one or more light emitting diodes (LEDs)  241   a - 241   d  are coupled to the antenna element selector as a visual indicator of which of the antenna elements  205   a - 205   d  is on or off. In one embodiment, a light emitting diode is placed in circuit with the PIN diode so that the light emitting diode is lit when the corresponding antenna element  205  is selected. 
     In some embodiments, the antenna components (e.g., the antenna elements  205   a - 205   d , the ground component  225 , the directors  210 , and the gain directors  215 ) are formed from RF conductive material. For example, the antenna elements  205   a - 205   d  and the ground component  225  may be formed from metal or other RF conducting foil. Rather than being provided on opposing sides of the substrate as shown in  FIGS. 2A and 2B , each antenna element  205   a - 205   d  is coplanar with the ground component  225 . In some embodiments, the antenna components may be conformally mounted to the housing of the system  100 . In such embodiments, the antenna element selector comprises a separate structure (not shown) from the antenna elements  205   a - 205   d . The antenna element selector may be mounted on a relatively small PCB, and the PCB may be electrically coupled to the antenna elements  205   a - 205   d . In some embodiments, the switch PCB is soldered directly to the antenna elements  205   a - 205   d.    
     In the embodiment of  FIG. 2B , the Y-shaped reflectors  235  (e.g., the reflectors  235   a ) may be included as a portion of the ground component  225  to broaden a frequency response (i.e., bandwidth) of the bent dipole (e.g., the antenna element  205   a  in conjunction with the portion  230   a  of the ground component  225 ). For example, in some embodiments, the planar antenna apparatus  110  is designed to operate over a frequency range of about 2.4 GHz to 2.4835 GHz, for wireless LAN in accordance with the IEEE 802.11 standard. The reflectors  235   a - 235   d  broaden the frequency response of each dipole to about 300 MHz (12.5% of the center frequency) to 500 MHz (˜20% of the center frequency). The combined operational bandwidth of the planar antenna apparatus  110  resulting from coupling more than one of the antenna elements  205   a - 205   d  to the radio frequency feed port  220  is less than the bandwidth resulting from coupling only one of the antenna elements  205   a - 205   d  to the radio frequency feed port  220 . For example, with all four antenna elements  205   a - 205   d  selected to result in an omnidirectional radiation pattern, the combined frequency response of the planar antenna apparatus  110  is about 90 MHz. In some embodiments, coupling more than one of the antenna elements  205   a - 205   d  to the radio frequency feed port  220  maintains a match with less than 10 dB return loss over 802.11 wireless LAN frequencies, regardless of the number of antenna elements  205   a - 205   d  that are switched on. 
       FIG. 3A  illustrates various radiation patterns resulting from selecting different antenna elements of the planar antenna apparatus  110  of  FIG. 2 , in one embodiment in accordance with the present invention.  FIG. 3A  depicts the radiation pattern in azimuth (e.g., substantially in the plane of the substrate of  FIG. 2 ). A line  300  displays a generally cardioid directional radiation pattern resulting from selecting a single antenna element (e.g., the antenna element  205   a ). As shown, the antenna element  205   a  alone yields approximately 5 dBi of gain. A dashed line  305  displays a similar directional radiation pattern, offset by approximately 90 degrees, resulting from selecting an adjacent antenna element (e.g., the antenna element  205   b ). A line  310  displays a combined radiation pattern resulting from selecting the two adjacent antenna elements  205   a  and  205   b . In this embodiment, enabling the two adjacent antenna elements  205   a  and  205   b  results in higher directionality in azimuth as compared to selecting either of the antenna elements  205   a  or  205   b  alone, with approximately 5.6 dBi gain. 
     The radiation pattern of  FIG. 3A  in azimuth illustrates how the selectable antenna elements  205   a - 205   d  may be combined to result in various radiation patterns for the planar antenna apparatus  110 . As shown, the combined radiation pattern resulting from two or more adjacent antenna elements (e.g., the antenna element  205   a  and the antenna element  205   b ) being coupled to the radio frequency feed port is more directional than the radiation pattern of a single antenna element. 
     Not shown in  FIG. 3A  for improved legibility, is that the selectable antenna elements  205   a - 205   d  may be combined to result in a combined radiation pattern that is less directional than the radiation pattern of a single antenna element. For example, selecting all of the antenna elements  205   a - 205   d  results in a substantially omnidirectional radiation pattern that has less directionality than that of a single antenna element. Similarly, selecting two or more antenna elements (e.g., the antenna element  205   a  and the antenna element  205   c  on opposite diagonals of the substrate) may result in a substantially omnidirectional radiation pattern. In this fashion, selecting a subset of the antenna elements  205   a - 205   d , or substantially all of the antenna elements  205   a - 205   d , may result in a substantially omnidirectional radiation pattern for the planar antenna apparatus  110 . 
     Although not shown in  FIG. 3A , it will be appreciated that additional directors (e.g., the directors  211 ) and/or gain directors (e.g., the gain directors  216 ) may further concentrate the directional radiation pattern of one or more of the antenna elements  205   a - 205   d  in azimuth. Conversely, removing or eliminating one or more of the directors  211 , the gain directors  216 , or the Y-shaped reflectors  235  expands the directional radiation pattern of one or more of the antenna elements  205   a - 205   d  in azimuth. 
       FIG. 3A  also shows how the planar antenna apparatus  110  may be advantageously configured, for example, to reduce interference in the wireless link between the system  100  of  FIG. 1  and a remote receiving node. For example, if the remote receiving node is situated at zero degrees in azimuth relative to the system  100  (at the center of  FIG. 3A ), the antenna element  205   a  corresponding to the line  300  yields approximately the same gain in the direction of the remote receiving node as the antenna element  205   b  corresponding to the line  305 . However, as can be seen by comparing the line  300  and the line  305 , if an interferer is situated at twenty degrees of azimuth relative to the system  100 , selecting the antenna element  205   a  yields approximately a 4 dB signal strength reduction for the interferer as opposed to selecting the antenna element  205   b . Advantageously, depending on the signal environment around the system  100 , the planar antenna apparatus  110  may be configured (e.g., by switching one or more of the antenna elements  205   a - 205   d  on or off) to reduce interference in the wireless link between the system  100  and one or more remote receiving nodes. 
       FIG. 3B  illustrates an elevation radiation pattern for the planar antenna apparatus  110  of  FIG. 2 . In the figure, the plane of the planar antenna apparatus  110  corresponds to a line from 0 to 180 degrees in the figure. Although not shown, it will be appreciated that additional directors (e.g., the directors  211 ) and/or gain directors (e.g., the gain directors  216 ) may advantageously further concentrate the radiation pattern of one or more of the antenna elements  205   a - 205   d  in elevation. For example, in some embodiments, the system  110  may be located on a floor of a building to establish a wireless local area network with one or more remote receiving nodes on the same floor. Including the additional directors  211  and/or gain directors  216  in the planar antenna apparatus  110  further concentrates the wireless link to substantially the same floor, and minimizes interference from RF sources on other floors of the building. 
       FIG. 4A  and  FIG. 4B  illustrate an alternative embodiment of the planar antenna apparatus  110  of  FIG. 1 , in accordance with the present invention. On the first side of the substrate as shown in  FIG. 4A , the planar antenna apparatus  110  includes a radio frequency feed port  420  and six antenna elements (e.g., the antenna element  405 ). On the second side of the substrate, as shown in  FIG. 4B , the planar antenna apparatus  110  includes a ground component  425  incorporating a number of Y-shaped reflectors  435 . It will be appreciated that a portion (e.g., the portion  430 ) of the ground component  425  is configured to form an arrow-shaped bent dipole in conjunction with the antenna element  405 . Similarly to the embodiment of  FIG. 2 , the resultant bent dipole has a directional radiation pattern. However, in contrast to the embodiment of  FIG. 2 , the six antenna element embodiment provides a larger number of possible combined radiation patterns. 
     Similarly with respect to  FIG. 2 , the planar antenna apparatus  110  of  FIG. 4  may optionally include one or more directors (not shown) and/or one or more gain directors  415 . The directors and the gain directors  415  comprise passive elements that concentrate the directional radiation pattern of the antenna elements  405 . In one embodiment, providing a director for each antenna element yields an additional 1-2 dB of gain for each element. It will be appreciated that the directors and/or the gain directors  415  may be placed on either side of the substrate. It will also be appreciated that additional directors and/or gain directors may be included to further concentrate the directional radiation pattern of one or more of the antenna elements  405 . 
     An advantage of the planar antenna apparatus  110  of  FIGS. 2-4  is that the antenna elements (e.g., the antenna elements  205   a - 205   d ) are each selectable and may be switched on or off to form various combined radiation patterns for the planar antenna apparatus  110 . For example, the system  100  communicating over the wireless link to the remote receiving node may select a particular configuration of selected antenna elements that minimizes interference over the wireless link. If the wireless link experiences interference, for example due to other radio transmitting devices, or changes or disturbances in the wireless link between the system  100  and the remote receiving node, the system  100  may select a different configuration of selected antenna elements to change the radiation pattern of the planar antenna apparatus  110  and minimize the interference in the wireless link. The system  100  may select a configuration of selected antenna elements corresponding to a maximum gain between the system and the remote receiving node. Alternatively, the system may select a configuration of selected antenna elements corresponding to less than maximal gain, but corresponding to reduced interference. Alternatively, all or substantially all of the antenna elements may be selected to form a combined omnidirectional radiation pattern. 
     A further advantage of the planar antenna apparatus  110  is that RF signals travel better indoors with horizontally polarized signals. Typically, network interface cards (NICs) are horizontally polarized. Providing horizontally polarized signals with the planar antenna apparatus  110  improves interference rejection (potentially, up to 20 dB) from RF sources that use commonly-available vertically polarized antennas. 
     Another advantage of the system  100  is that the planar antenna apparatus  110  includes switching at RF as opposed to switching at baseband. Switching at RF means that the communication device  120  requires only one RF up/down converter. Switching at RF also requires a significantly simplified interface between the communication device  120  and the planar antenna apparatus  110 . For example, the planar antenna apparatus provides an impedance match under all configurations of selected antenna elements, regardless of which antenna elements are selected. In one embodiment, a match with less than 10 dB return loss is maintained under all configurations of selected antenna elements, over the range of frequencies of the 802.11 standard, regardless of which antenna elements are selected. 
     A still further advantage of the system  100  is that, in comparison for example to a phased array antenna with relatively complex phase switching elements, switching for the planar antenna apparatus  110  is performed to form the combined radiation pattern by merely switching antenna elements on or off. No phase variation, with attendant phase matching complexity, is required in the planar antenna apparatus  110 . 
     Yet another advantage of the planar antenna apparatus  110  on PCB is that the planar antenna apparatus  110  does not require a 3-dimensional manufactured structure, as would be required by a plurality of “patch” antennas needed to form an omnidirectional antenna. Another advantage is that the planar antenna apparatus  110  may be constructed on PCB so that the entire planar antenna apparatus  110  can be easily manufactured at low cost. One embodiment or layout of the planar antenna apparatus  110  comprises a square or rectangular shape, so that the planar antenna apparatus  110  is easily panelized. 
     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.