HK1180836B - Multiband omnidirectional planar antenna apparatus with selectable elements - Google Patents

Description

Multi-band omni-directional planar antenna apparatus with selectable elements

The present invention is a divisional application of an invention patent application having an application date of 12/4/2007 and an application number of "200780020943.9", entitled "multiband omnidirectional planar antenna apparatus with selectable elements".

Technical Field

The present invention relates generally to wireless communication networks and more particularly to a multi-band omni-directional planar antenna apparatus with selectable elements.

Background

In communication systems, there is an increasing demand for higher data throughput, and there is a corresponding drive to reduce interference that can disrupt data communications. For example, in a network of the IEEE802.11 standard, an access point (i.e., a base station) communicates data with one or more remote receiving nodes (i.e., a network interface card) via a wireless link. Wireless links may be susceptible to interference from other access points, other radio transmission devices, changes or disturbances in the wireless link environment between an access point and a remote receiving node, and so forth. The interference may degrade the wireless link, for example by forcing communication to occur at a lower data rate, or may be strong enough to completely disrupt the wireless link.

One solution for reducing interference in the wireless link between an access point and a remote receiving node is to provide several omnidirectional antennas for the access point in a "diversity" scheme. For example, a common configuration for an access point includes a data source coupled to two or more physically separated omnidirectional antennas via a switching network. The access point may select one of the omnidirectional antennas to thereby maintain the wireless link. Because of the separation between the omnidirectional antennas, each antenna is subject to a different signal environment, and each antenna provides a different interference level to the wireless link. The switching network couples the data source to any of the omnidirectional antennas that experiences the least interference in the wireless link.

However, one problem with using two or more omnidirectional antennas for an access point is that typical omnidirectional antennas are vertically polarized. Vertically polarized Radio Frequency (RF) energy does not propagate as efficiently in a typical office or living space as horizontally polarized RF energy, and in addition, most laptop computer wireless cards have horizontally polarized antennas. Heretofore, common solutions for manufacturing horizontally polarized RF antennas have been expensive to manufacture or have not provided sufficient RF performance to be commercially successful.

A further problem is that omni-directional antennas generally include an upstanding pole attached to the access point housing. The rod typically comprises a hollow metal rod exposed to the exterior of the housing and is subject to breakage or damage. Another problem is that each omnidirectional antenna comprises a separate manufacturing unit with respect to the access point, thus requiring additional manufacturing steps to include the omnidirectional antenna in the access point.

A further problem with using two or more omnidirectional antennas is that because physically separate antennas may still be relatively close to each other, each of the several antennas may suffer from similar interference levels, and by switching from one omnidirectional antenna to another, only a relatively small reduction in interference may be obtained.

Another solution to reduce interference involves beam steering using electronically controlled phased array antennas. However, phased array antennas are extremely expensive to manufacture. Further, phased array antennas require many phase tuning elements, which may drift or become detuned.

Further, it is not a trivial task to incorporate multi-band coverage into an access point having one or more omnidirectional antennas. Typically, antennas operate well in one frequency band but do not operate or give suboptimal performance in another frequency band. Providing multi-band coverage into an access point may require a large number of antennas, each tuned to operate at a different frequency.

The large number of antennas may cause the access point to appear as an unsightly "antenna field". Antenna fields are particularly unsuitable for home consumer applications because the large number of antennas that must be separated may require the overall size of the access point to be increased, which most consumers would like to be as small and unobtrusive as possible.

Disclosure of Invention

In one aspect, an antenna apparatus includes: the antenna device includes: a substrate having a first layer and a second layer; a plurality of antenna elements on a first layer, each active antenna element selectively coupled to a communication device, at least one active antenna element configured to form a first portion of a dipole having a directional radiation pattern with a polarization substantially in the plane of the substrate, a first active antenna element configured to operate at a first frequency; and a ground component on a second side of the substrate, the ground component forming a second portion of the first dipole, the second portion of the dipole being asymmetric with respect to a plane of symmetry between the first and second portions of the dipole.

In one aspect, a system comprises: communication means for generating a low band RF or a high band RF; first means for generating a first directional radiation pattern; second means for generating a second directional radiation pattern; and a selection device for receiving the low band RF or the high band RF from the communication device and selectively coupling the first device or the second device to the communication device.

In one aspect, a method comprises: generating a first radio frequency signal in a communication device; and coupling at least one of the plurality of co-planar antenna elements to the communication device to produce a first directional radiation pattern substantially in the plane of the antenna element, the plurality of co-planar antenna elements configured to be coupled to the communication device to provide a plurality of directional radiation patterns.

In one aspect, an antenna apparatus includes a substrate having a first layer and a second layer. The antenna element on the first layer includes: a first dipole component configured to radiate at a first radio frequency (e.g., a low band of approximately 2.4 to 2.4835 GHz); and a second dipole component configured to radiate at a second radio frequency (e.g., a high-band of approximately 4.9 to 5.825 GHz). The ground components on the second layer include respective portions of the first dipole component and respective portions of the second dipole component.

The antenna apparatus may include a plurality of antenna elements and an antenna element selector coupled to the plurality of antenna elements. The antenna element selector is configured to selectively couple the antenna element to a communication device for generating a first radio frequency and a second radio frequency. The antenna element selector may comprise a PIN diode network. The antenna element selector may be configured to simultaneously couple the first plurality of antenna elements to a first radio frequency and the second plurality of antenna elements to a second radio frequency.

In one aspect, a method comprises: generating a low band RF; generating a high band RF; coupling low-band RF to a first plurality of planar antenna elements; and RF coupling the high-band RF to the second plurality of planar antenna elements. The first group may not include antenna elements included in the second group of antenna elements, and may include one or more of the antenna elements. The first set of antenna elements may be configured to radiate at a different orientation relative to the second set of antenna elements or may be configured to radiate at approximately the same orientation relative to the second set of antenna elements.

In one aspect, a multiband coupling network comprises: a feed port configured to receive a low band RF or a high band RF; a first filter configured to pass the low band RF and shift the low band RF with a predetermined delay; and a second filter connected in parallel with the first filter. The second filter is configured to pass and shift the high-band RF with a predetermined delay.

The predetermined delay may comprise 1/4 wavelengths or an odd multiple thereof. The multiband coupling network may include an RF switch network configured to selectively couple the feed port to the first filter or the second filter. The multiband coupling network may include: a first PIN diode network configured to selectively couple the feed port to the first filter; and a second PIN diode network configured to selectively couple the feed port to the second filter.

In one aspect, a multiband coupling network comprises: a feed port configured to receive a low band RF or a high band RF; a first switch coupled to the feed port; a second switch coupled to the feed port; a first set of coupled lines (e.g., curved traces) coupled to the first switch and configured to pass low band RF; and a second set of coupled lines coupled to the second switch and configured to pass the high band RF. The first switch and the first set of coupled lines may include a delay of 1/4 wavelengths for low band RF and the second switch and the second set of coupled lines may include a delay of 1/4 wavelengths for high band RF.

Drawings

The present invention will now be described with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. In the drawings, like parts have like reference numerals. The illustrated embodiments are intended to illustrate, but not to limit the invention. The drawings include the following figures:

fig. 1 illustrates a system including an omnidirectional planar antenna apparatus with selectable elements in accordance with one embodiment of the present invention;

fig. 2A and 2B illustrate the planar antenna apparatus of fig. 1 according to one embodiment of the present invention;

figures 2C and 2D (collectively figures 2 with figures 2A and 2B) illustrate dimensions of several components of the planar antenna apparatus of figure 1 in accordance with one embodiment of the present invention;

fig. 3A illustrates various radiation patterns resulting from selecting different antenna elements of the planar antenna apparatus of fig. 2, in accordance with one embodiment of the present invention;

fig. 3B (collectively fig. 3 with fig. 3A) illustrates a bottom radiation pattern for the planar antenna apparatus of fig. 2 in accordance with one embodiment of the present invention;

fig. 4A and 4B (collectively fig. 4) illustrate an alternative embodiment of the planar antenna apparatus 110 of fig. 1 in accordance with the present invention;

fig. 5 illustrates one element of a multiband antenna element for use in the planar antenna apparatus of fig. 1, according to one embodiment of the present invention;

FIG. 6 illustrates a multiband coupling network for coupling the multiband antenna element of FIG. 5 to the multiband communication device of FIG. 1, according to one embodiment of the invention;

fig. 7 illustrates an enlarged view of a partial PCB layout for a multiband coupling network between the multiband communication device of fig. 1 and the multiband antenna element of fig. 5, according to one embodiment of the invention; and

fig. 8 illustrates an enlarged view of a partial PCB layout for a multiband coupling network between the multiband communication device of fig. 1 and the multiband antenna element of fig. 5, according to one embodiment of the invention.

Detailed Description

A system for wireless (i.e., radio frequency or RF) linking to a remote receiving device comprises: communication means for generating an RF signal; and a planar antenna apparatus for transmitting and/or receiving RF signals. The planar antenna apparatus includes selectable antenna elements. Each antenna element provides gain (relative to isotropic) and a directional radiation pattern substantially in the plane of the antenna element. 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, the planar antenna apparatus may form a substantially omnidirectional radiation pattern if two or more elements are switched on.

Advantageously, the system may select a particular configuration of selected antenna elements that minimizes interference to the remote receiving device via the wireless link. If the wireless link is subject to interference, for example due to other radio transmitting devices or due to 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 the selected antenna elements that corresponds to a maximum gain between the system and the remote receiving device. Alternatively, the system may select a configuration of selected antenna elements that corresponds to a gain less than the maximum gain but corresponds to reduced interference in the wireless link.

As described further herein, the planar antenna apparatus radiates a directional radiation pattern substantially in the plane of the antenna elements. When horizontally mounted, RF signal transmission is horizontally polarized, so indoor RF signal transmission is enhanced compared to a vertically polarized antenna. Planar antenna devices are readily manufactured from common planar substrates such as FR4 Printed Circuit Boards (PCBs). Further, the planar antenna apparatus may be integrated into or conformally mounted to a housing of the system to minimize cost and provide support for the planar antenna apparatus.

Fig. 1 illustrates a system 100 including an omnidirectional planar antenna apparatus with selectable elements in accordance with one embodiment of the present invention. System 100 may include, for example and without limitation, a transmitter and/or receiver such as an 802.11 standard access point, an 802.11 standard 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 demonstrative embodiments, system 100 includes an access point for communicating with one or more remote receiving nodes (not shown) via a wireless link, e.g., in an 802.11-standard 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 remote receiving nodes. System 100 may also form part of a wireless local area network by enabling communication between several remote receiving nodes. While the present disclosure will focus on a particular embodiment of the system 100, the aspects of the present invention are applicable to a wide variety of installations and are not intended to be limited to the disclosed embodiments. For example, although system 100 may be described as being transmitted to a remote receiving node via a planar antenna apparatus, system 100 may also receive data from a remote receiving node via a planar antenna apparatus.

The system 100 includes a communication device 120 (e.g., a transceiver) and a planar antenna apparatus 110. Communication device 120 includes virtually any device for generating and/or receiving RF signals. The communication device 120 may include, for example, a radio modulator/demodulator for converting data received into the system 100 (e.g., from a router) into RF signals for transmission to one or more remote receiving nodes. For example, in some embodiments, the communication device 120 includes well-known circuitry for receiving video data packets from a router and circuitry for converting the data packets into RF signals conforming to the 802.11 standard.

As further described herein, the planar antenna apparatus 110 includes a plurality of individually selectable planar antenna elements. Each antenna element has a directional radiation pattern with a gain (compared to an omni-directional antenna). Each antenna element also has a polarization substantially in the plane of the planar antenna apparatus 110. The planar antenna apparatus 110 may include an antenna element selection device configured to selectively couple one or more antenna elements to the communication device 120.

Fig. 2A and 2B illustrate the planar antenna apparatus 110 of fig. 1 according to one embodiment of the present invention. The planar antenna apparatus 110 of this embodiment includes a substrate (considered to be the plane of fig. 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, Rogers4003, or other dielectric material.

On the first side of the substrate, the planar antenna apparatus 110 of fig. 2A comprises a radio frequency feed port 220 and four antenna elements 205a-205 d. As described with respect to fig. 4, although four antenna elements are depicted, it is contemplated that more or fewer antenna elements may be used. Although the antenna elements 205a-205d of fig. 2A are oriented substantially on the diagonals of a square planar antenna in order to minimize the size of the planar antenna apparatus 110, other shapes are contemplated. Further, although the antenna elements 205a-205d form a radially symmetric layout with respect to the radio frequency feed port 220, many asymmetric layouts, rectangular layouts, and layouts that are symmetric about only one axis are contemplated. Further, the antenna elements 205a-205d need not be the same size, 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 member 225. It will be appreciated that a portion (e.g., 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 resulting bent dipole provides a directional radiation pattern substantially in the plane of the planar antenna apparatus 110, as further described with respect to fig. 3.

Fig. 2C and 2D illustrate dimensions of several components of the planar antenna apparatus 110 according to one embodiment of the present invention. It will be appreciated that the dimensions of the various components of the planar antenna apparatus 110 (e.g., the antenna element 205a, the portion 230a of the ground component 205) are dependent upon the desired operating frequency of the planar antenna apparatus 110. The dimensions of the various components may be established using RF simulation software such as IE3D from zelandsoftwareffremont, CA. For example, a planar antenna apparatus 110 comprising components of dimensions according to fig. 2C and 2D is designed to operate around 2.4GHz based on a substrate PCB of Rogers4003 material, but a state of the art antenna designer will appreciate that different substrates with different dielectric properties, such as FR4, may require different dimensions compared to those shown in fig. 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., Y-shaped reflector 235B depicted in fig. 2B and 2D). The directors 210, the gain directors 215, and the Y-shaped reflectors 235 include passive elements that concentrate the directional radiation pattern of the dipoles formed by the antenna elements 205a-205d in conjunction with the sections 230a-230 d. In one embodiment, providing the directors 210 for each of the antenna elements 205a-205d results in an additional 1-2dB of gain for each dipole. It will be appreciated that the directors 210 and/or the gain directors 215 may be disposed on either side of the substrate. In some embodiments, the portion of the substrate for the directors 210 and/or gain directors 215 is marked so that the directors 210 and/or gain directors 215 may be removed. It will also be appreciated that additional directors (depicted in the location shown by dashed line 211 for the antenna element 205 b) and/or additional gain directors (depicted in the location shown by dashed line 216) may be included to further concentrate the directional radiation pattern of one or more dipoles. The Y-shaped reflector 235 will be further described herein.

The radio frequency feed port 220 is configured to receive RF signals from the communication device 120 of fig. 1 and/or transmit RF signals 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 205a-205 d. The antenna element selector may include an RF switch (not shown) such as a PIN diode, GaAsFET, or virtually any RF switching device, as is well known in the art.

In the embodiment of fig. 2A, the antenna element selector includes four PIN diodes, each PIN diode connecting one of the antenna elements 205a-205d to the radio frequency feed port 220. In this embodiment, the PIN diode includes a single pole, single throw switch to turn each antenna element on or off (i.e., to couple or decouple each of the antenna elements 205a-205d to the radio frequency feed port 220). In one embodiment, a series of control signals (not shown) are used to bias each PIN diode. With the PIN diode forward biased and conducting DC current, the PIN diode switch turns on and the corresponding antenna element is selected. With the PIN diode reverse biased, the PIN diode switch is open. In this embodiment, the radio frequency feed port 220 and the PIN diode of the antenna element selector are located on the side of the substrate having the antenna elements 205a-205d, however, other embodiments separate the radio frequency feed port 220, the antenna element selector and the antenna elements 205a-205 d. In some embodiments, the antenna element selector comprises one or more single-pole, multi-throw switches. In some embodiments, one or more light emitting diodes (not shown) are coupled to the antenna element selector as a visual indicator of which of the antenna elements 205a-205d is on or off. In one embodiment, the light emitting diodes are in circuit with the PIN diodes so that the light emitting diodes are illuminated when the corresponding antenna element 205 is selected.

In some embodiments, the antenna components (e.g., the antenna elements 205a-205d, the ground component 225, the director 210 and the gain director 215) are formed of an RF conductive material. For example, the antenna elements 205a-205d and the ground component 225 may be formed from metal or other RF conductive foil. Rather than being provided on opposite sides of the substrate as shown in fig. 2A and 2B, each of the antenna elements 205a-205d 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 an embodiment, the antenna element selector includes a separate structure (not shown) from the antenna elements 205a-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 205a-205 d. In some embodiments, the switch PCB is soldered directly to the antenna elements 205a-205 d.

In the embodiment of fig. 2B, a Y-shaped reflector 235 (e.g., reflector 235 a) may be included as part of the ground component 225 to broaden the frequency response (i.e., bandwidth) of the bent dipole (e.g., the antenna element 205a in conjunction with the portion 230a of the ground component 225). For example, in some embodiments, the planar antenna apparatus 110 is designed to operate over a frequency range of approximately 2.4GHz to 2.4835GHz for a wireless LAN in accordance with the IEEE802.11 standard. Reflectors 235a-235d broaden the frequency response of each dipole to approximately 300MHz (12.5% of center frequency) to 500MHz (20% of center frequency). Coupling more than one antenna element 205a-205d to the radio frequency feed port 220 results in a combined operating bandwidth of the planar antenna apparatus 110 that is less than the bandwidth resulting from coupling only one of the antenna elements 205a-205d to the radio frequency feed port 220. For example, where all four antenna elements 205a-205d are selected to produce an omnidirectional radiation pattern, the combined frequency response of the planar antenna apparatus 110 is about 90 MHz. In some embodiments, the coupling of more than one antenna element 205a-205d to the radio frequency feed port 220 can maintain a match with less than 10dB return loss over 802.11 standard wireless LAN frequencies, regardless of the number of antenna elements 205a-205d that are switched on.

Fig. 3A illustrates various radiation patterns resulting from the selection of different antenna elements of the planar antenna apparatus 110 of fig. 2, in accordance with one embodiment of the present invention. Fig. 3A depicts a radiation pattern in azimuth (e.g., substantially in the plane of the substrate of fig. 2). Line 300 shows the generally cardioid directional radiation pattern resulting from selecting a single antenna element (e.g., antenna element 205 a). As shown, the antenna element 205a alone achieves a gain of approximately 5 dBi. The dashed line 305 shows a similar directional radiation pattern offset by approximately 90 degrees resulting from selecting an adjacent antenna element (e.g., the antenna element 205 b). The line 310 shows the combined radiation pattern resulting from the selection of the two adjacent antenna elements 205a and 205 b. In this embodiment, selecting two adjacent antenna elements 205a and 205b results in higher directivity in azimuth, with approximately 5.6dBi gain, than selecting either of the antenna elements 205a or 205b alone.

The radiation pattern of fig. 3A illustrates in azimuth how the selectable antenna elements 205a-205d may be combined to produce various radiation patterns for the planar antenna apparatus 110. As shown, coupling two or more adjacent antenna elements (e.g., antenna element 205a and antenna element 205 b) to the radio frequency feed port results in a combined radiation pattern that is more directional than the radiation pattern of a single antenna element.

Not shown in fig. 3A for improved readability, the selectable antenna elements 205a-205d may be combined to produce 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 205a-205d may result in a substantially omnidirectional radiation pattern that is less directional than the radiation pattern of a single antenna element. Similarly, selecting two or more antenna elements (e.g., antenna element 205a and antenna element 205c on opposite diagonals of the substrate) may result in a substantially omnidirectional radiation pattern. In this manner, selecting a subset of the antenna elements 205a-205d or substantially all of the antenna elements 205a-205d 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 205a-205d 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 205a-205d in azimuth.

Fig. 3A also shows how the planar antenna apparatus 110 may be advantageously configured, for example, to reduce interference in a wireless link between the system 100 of fig. 1 and a remote receiving node. For example, if the remote receiving node is located at zero degrees in azimuth with respect to system 100 (at the center of fig. 3A), antenna element 205a corresponding to line 300 gains approximately the same gain in the direction of the remote receiving node as antenna element 205b corresponding to line 305. However, as can be seen by comparing line 300 with line 305, if the interfering signal is located twenty degrees in azimuth with respect to the system 100, selecting the antenna element 205a results in an approximately 4dB signal strength reduction for the interfering signal, as opposed to selecting the antenna element 205 b. Advantageously, depending on the signal environment surrounding the system 100, the planar antenna apparatus 110 may be configured to reduce interference in the wireless link between the system 100 and one or more remote receiving nodes (e.g., by switching one or more of the antenna elements 205a-205d on or off).

Fig. 3B illustrates an elevation radiation pattern for the planar antenna apparatus 110 of fig. 2. In the drawing, the plane of the planar antenna apparatus 110 corresponds to a line from 0 to 180 degrees in the drawing. 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 205a-205d in azimuth. 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. The inclusion of the further directors 211 and/or the gain directors 216 in the planar antenna apparatus 110 further concentrates the wireless links to substantially the same floor and minimizes interference from RF sources on other floors of the building.

Fig. 4A and 4B illustrate alternative embodiments 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., antenna element 405). On the second side of the substrate, as shown in fig. 4B, the planar antenna apparatus 110 comprises a grounding part 425, the grounding part 425 comprising a number of Y-shaped reflectors 435. It will be appreciated that a portion (e.g., portion 430) of the ground component 425 is configured to form an arrow-shaped bent dipole in conjunction with the antenna element 405. Similar to the embodiment of fig. 2, the resulting 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.

Similar 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 gain directors 415 include passive elements that concentrate the directional radiation pattern of the antenna element 405. In one embodiment, providing a director for each antenna element results in an additional 1-2dB of gain for each element. It will be appreciated that directors and/or 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 fig. 2-4 is that the antenna elements (e.g., the antenna elements 205a-205 d) are each selectable and can be switched on or off to form various combined radiation patterns for the planar antenna apparatus 110. For example, the system 100 communicating with a remote receiving node via a wireless link may select a particular configuration of selected antenna elements that minimizes interference over the wireless link. If the wireless link is subject to interference, for example due to other radio transmission means or due to changes or disturbances in the wireless link between the system 100 and a 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. System 100 may select a configuration of selected antenna elements that corresponds to a maximum gain between the system and a remote receiving node. Alternatively, the system may select a configuration of selected antenna elements that corresponds to a gain less than the maximum gain but corresponds 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 can be better propagated indoors using horizontally polarized signals. Typically, Network Interface Cards (NICs) are horizontally polarized. Providing a horizontally polarized signal to the planar antenna apparatus 110 improves interference rejection (potentially up to 20 dB) for RF sources using commonly available vertically polarized antennas.

Another advantage of the system 100 is that the planar antenna apparatus 110 includes switching in an RF manner, as opposed to switching in a baseband manner. Switching in RF mode means that only one RF up/down converter is required for the communication device 120. Switching in RF mode also requires a significantly simplified interface between the communication device 120 and the planar antenna apparatus 110. For example, the planar antenna apparatus provides impedance matching under all configurations of selected antenna elements regardless of which antenna elements are selected. In one embodiment, over the range of frequencies of the 802.11 standard, a match with less than 10dB return loss is maintained under all configurations of selected antenna elements, regardless of which antenna elements are selected.

A still further advantage of the system 100 is that the switching for the planar antenna apparatus 110 can be performed by merely switching antenna elements on or off to form a combined radiation pattern, as compared to, for example, a phased array antenna with relatively complex phase switching elements. Phase variations with attendant phase matching complexity are not required in the planar antenna apparatus 110.

Yet another advantage of the planar antenna apparatus 110 on a PCB is that the planar antenna apparatus 110 does not require a three-dimensional fabrication structure, as would be required by the multiple "patch" antennas required to form an omnidirectional antenna. Another advantage is that the planar antenna apparatus 110 may be constructed on a PCB, so the entire planar antenna apparatus 110 can be easily manufactured at low cost. One embodiment or layout of the planar antenna apparatus 110 includes a square or rectangular shape, so the planar antenna apparatus 110 is easily planarized.

Multiband antenna apparatus

Fig. 5 illustrates one element of a multiband antenna element 510 for use in the planar antenna apparatus 110 of fig. 1, according to one embodiment of the invention. In embodiments for multi-band operation (e.g., dual bands with low and high bands; tri-bands with low, mid, and high bands; etc.), communication device 120 includes a "multi-band" device that has the ability to generate and/or receive RF signals at frequencies of more than one band.

As described further herein, in some embodiments (e.g., for a network interface card or NIC), the communication device 120 alternates operation (e.g., for the 802.11 standard) between a low frequency band of approximately 2.4 to 2.4835GHz or a high frequency band of approximately 4.9 to 5.35GHz and/or 5.725 to 5.825GHz, and switches between frequency bands at a relatively low rate on the order of minutes or days. The multiband antenna element 510 and the multiband coupling networks of fig. 6-8 allow the NIC to operate on the configuration of the selected antenna element 510. For example, the NIC may transmit low band RF in a directional or omnidirectional pattern by selecting a set of one or more multiband antenna elements 510.

In some embodiments, such as in an access point for the 802.11 standard, the communication device 120 switches between frequency bands at a relatively high rate (e.g., changes from a low frequency band to a high frequency band for each packet to be transmitted such that the switch requires time on the order of milliseconds). For example, the access point may transmit a first packet to a receiving node at low-band RF on a selected multiband antenna element 510 of a first configuration (directional or omnidirectional mode). The access point may then switch to the selected multiband antenna element 510 of the second configuration to transmit the second packet.

In other embodiments, the multiband communication device 120 comprises multiple MACs to allow simultaneous independent operation of multiple bands through the independently selectable multiband antenna element 510. In simultaneous operation for multiple bands, the multi-band communication device 120 may, for example, generate low and high band RF to increase the data rate to a remote receiving node. With simultaneous multiband capability, system 100 (fig. 1) may transmit a low-band to a first remote receiving node via a first configuration (set) of selected multiband antenna elements 510 while transmitting a high-band to a second remote receiving node via a second configuration (set) of selected multiband antenna elements 510. The selected multiband antenna elements 510 of the first and second configurations or sets may be the same or different.

For ease of illustration of the multiband antenna element 510, only a single multiband antenna element 510 is shown in fig. 5. The multiband antenna element 510 may be used in place of one or more of the antenna elements 205a-d, the portions 230a-d of the respective ground component 225, and the reflectors 235a-d of fig. 2. Alternatively, the multiband antenna element 510 may be used in place of one or more of the antenna element 405 and the portion 430 of the ground component 425 of fig. 4. As described with respect to fig. 2 to 4, configurations other than the 4-element configuration and the 6-element configuration may be considered for use.

In some embodiments, the multiband antenna element 510 comprises a substrate (considered to be the plane of fig. 5) having two layers. In a preferred embodiment, the substrate may have four layers, although the substrate may have any number of layers. Fig. 5 illustrates the multiband antenna element 510 as it would appear in an X-ray film of the substrate.

In some embodiments, the substrate comprises a PCB such as FR4, Rogers4003, or other dielectric material, wherein the multiband antenna element 510 is formed from traces on the PCB. Although the remainder of this description will focus on the multiband antenna element 510 being formed on separate layers of the PCB, in some embodiments, the multiband antenna element 510 is formed of RF conductive material such that the components of the multiband antenna element 510 can be coplanar or on a single layer so that the antenna apparatus 110 can be conformally mounted, for example.

On a first layer of the substrate, depicted with solid lines (e.g., traces on a PCB), the multiband antenna element 510 includes a first dipole component 515 and a second dipole component 525. The second dipole component 525 is configured to form a dual resonance structure with the first dipole component 515. The dual resonance structure widens the frequency response of the multiband antenna element 510.

Further, the second dipole component 525 can optionally include a notch or "stair-step" structure 530. The stepped structure 530 further widens the frequency response of the second dipole component 525. In some embodiments, the stepped structure 530 widens the frequency response of the second dipole component 525 such that it can radiate over a wide range of frequencies from about 4.9 to 5.825 GHz.

On the second, third and/or fourth layers of the substrate, the multiband antenna element 510 has a ground component depicted with a dashed line in fig. 5. The grounding component includes a corresponding portion 535 for the first dipole component 515 and a corresponding portion 545 for the second dipole component 525. As depicted in fig. 5, the dipole component and the respective portions of the ground component need not be 180 degrees opposite each other so that the dipole component forms a "T," but rather the dipole component can be angled so as to create an arrow shape. For example, the first dipole component 515 is angled approximately 120 degrees relative to the corresponding portion 535 for inclusion within a hexagonal substrate having six multiband antenna elements 510.

The ground members optionally include a first reflector member 555, the first reflector member 555 configured to concentrate the radiation pattern and broaden the frequency response (bandwidth) of the first dipole member 515 and corresponding portion 535. The ground component further comprises a second reflector component 565, the second reflector component 565 configured to concentrate the radiation pattern and broaden the frequency response (bandwidth) of the second dipole component 525 and the corresponding portion 545.

Optional directors and/or gain directors oriented relative to the multiband antenna element 510 are not shown in fig. 5. Passive elements such as those described with respect to fig. 2-4 may be included on the substrate to concentrate the directional radiation pattern of a first dipole formed by first dipole component 515 in conjunction with corresponding portion 535 and/or to concentrate the directional radiation pattern of a second dipole formed by second dipole component 525 in conjunction with corresponding portion 545.

In operation, low-band and/or high-band RF energy to/from the multi-band communication device 120 is coupled into the point labeled "a" in fig. 5 via the multi-band coupling network described further with respect to fig. 6-8. The first dipole component 515 and corresponding portion 535 are configured to radiate at a first frequency of a lower frequency band of approximately 2.4 to 2.4835 GHz. The second dipole component 525 and corresponding portion 545 are configured to radiate at a second frequency. In some embodiments, the second frequency is in the range of about 4.9 to 5.35 GHz. In other embodiments, the second frequency is in the range of approximately 5.725 to 5.825 GHz. In still other embodiments, the second frequency is within a wide range of about 4.9 to 5.825 GHz.

RF simulation software such as IE3D may be used to determine the dimensions of the individual components of the multiband antenna element 510, as described herein. As is well known to those skilled in the art, the dimensions of the individual components depend, among other factors, on the desired operating frequency.

Fig. 6 illustrates a multiband coupling network 600 for coupling the multiband antenna element 510 of fig. 5 to the multiband communication device 120 of fig. 1, according to one embodiment of the invention. For clarity, only a single multiband antenna element 510 and multiband coupling network 600 are shown, although multiband coupling network 600 is generally included for each multiband antenna element 510 in the planar antenna apparatus 110 of fig. 1. Although described as a dual-band embodiment, the multiband coupling network 600 may be modified to implement virtually any number of frequency bands.

As described with respect to fig. 2-4, the radio frequency feed port 220 provides an interface to the multiband communication device 120, for example, as an accessory to a coaxial cable from the communication device 120. In the low band RF path, a first RF switch 610, such as a PIN diode, GaAsFET, or virtually any RF switching device known in the art (shown schematically as a PIN diode), selectively couples the radio frequency feed port 220 to point a of the multiband antenna element 510 through a low band filter (also referred to as a band pass filter or BPF) 620. The low band filter 620 includes well known circuits including resistors, capacitors, and/or inductors configured to pass low band frequencies and not pass high band frequencies. The low band control signal (LBCTRL) may be pulled or biased low to turn on the RF switch 610.

In the high-band RF path, a second RF switch 630 (shown schematically as a PIN diode) selectively couples the radio frequency feed port 220 to point a of the multiband antenna element 510 through the high-band filter 640. The high-band filter 640 includes well-known circuits including resistors, capacitors, and/or inductors configured to pass high-band frequencies and not pass low-band frequencies. The high-band control signal (HBCTRL) may be "pulled low" to turn on the RF switch 630. A DC blocking capacitor (not labeled) prevents the control signal from interfering with the RF path.

As further described with respect to fig. 7 and 8, the low band RF path and the high band RF path may have the same predetermined path delay. Having the same path delay, e.g., 1/4 wavelengths for both the low band and the high band, simplifies matching in the multiband coupling network 600.

The multiband coupling network 600 allows for full-duplex, simultaneous and independent selection of multiband antenna elements 510 for low and high frequency bands. For example, in a 4-element configuration similar to fig. 2, where each antenna element includes a multiband coupling network 600 and multiband antenna elements 510, a first set of two multiband antenna elements 510 may be selected for the low band, while at the same time a different set of three multiband antenna elements 510 may be selected for the high band. In this manner, low-band RF can be transmitted in one radiation pattern or directional orientation for a first packet and high-band RF can be simultaneously transmitted in another radiation pattern or directional orientation for a second packet (assuming multi-band communication device 120 includes two separate MACs).

Fig. 7 illustrates an enlarged view of a partial PCB layout for the multiband coupling network 700 between the multiband communication device 120 of fig. 1 and the multiband antenna element 510 of fig. 5, according to one embodiment of the invention. For clarity, only one multiband antenna element 510 is shown, although the multiband coupling network 700 may be used for each multiband antenna element 510 included in the planar antenna apparatus 110. The embodiment of fig. 7 may be used for a multi-band communication device 120 that uses full duplex, simultaneous operation for the low and high frequency bands, as described with respect to fig. 6, for the multi-band communication device 120. Although described as a dual-band embodiment, it will be apparent to those skilled in the art that the multiband coupling network 700 may be modified to implement virtually any number of frequency bands.

In general, the multiband coupling network 700 is similar in principle to the multiband coupling network of fig. 6, however, the bandpass filter includes coupled lines (traces) 720 and 740 on a substrate (PCB). The coupled lines 720 include curved lines configured to pass low-band frequencies from about 2.4 to 2.4835 GHz. The physical length of the coupled line 720 is determined such that the low-band frequency of the coupled line 720 at the output of point a is delayed 1/4 wavelengths (or an odd multiple thereof) relative to the radio frequency feed port 220.

Coupled line 740 is also formed from traces on the PCB and is configured as a BPF to pass high-band frequencies from about 4.9 to 5.825 GHz. The physical length of the coupled line 740 is determined such that the coupled line 740 is delayed 1/4 wavelengths (or an odd multiple thereof) relative to the radio frequency feed port 220 at the low-band frequency at the output of point a.

A first RF switch 710, such as a PIN diode, GaAsFET, or nearly any RF switching device known in the art (shown schematically as a PIN diode), selectively couples the radio frequency feed port 220 to point a of the multiband antenna element 510 through the low band coupled line 720. The low band control signal (LBCTRL) and the DC blocking capacitor (not labeled) are configured to turn on/off the RF switch 710.

A second RF switch 730, such as a PIN diode, GaAsFET, or virtually any RF switching device known in the art, selectively couples the radio frequency feed port 220 to the point a of the multiband antenna element 510 through the high-band coupled line 740. The high band control signal (HBCTRL) and DC blocking capacitor (not labeled) are configured to turn on/off the RF switch 740.

An advantage of multiband coupling network 700 is that coupled lines 720 and 740 comprise traces on the substrate, so that the coupled lines can be fabricated within a very small area on the substrate. Further, the coupled lines 720 and 740 do not require components such as resistors, capacitors, and/or inductors or duplexers, and are substantially freely included on the substrate.

Another advantage is that the 1/4 wavelength of coupled line 720 is located at the same point as the 1/4 wavelength of coupled line 740. For example, if the RF switch 710 or 730 is open, indicating a high impedance, there is no or minimal effect at point A. The multiband coupling network 700 thus allows for independent coupling of low-band and/or high-band to the multiband antenna element 510.

Further, in one embodiment, only one DC blocking capacitor is included after RF switches 710 and 730 because coupled lines 720 and 740 are effective in blocking DC. Such a configuration further reduces the size and cost of the multiband coupling network 700.

Fig. 8 illustrates an enlarged view of a partial PCB layout for the multiband coupling network 800 between the multiband communication device 120 of fig. 1 and the multiband antenna element 510 of fig. 5, according to one embodiment of the invention. For clarity, only one multiband antenna element 510 is shown, although the multiband coupling network 800 may be used for each multiband antenna element 510 included in the planar antenna apparatus 110. The embodiment of fig. 8 may be used for a multi-band communication device 120, which multi-band communication device 120 may alternatively use one frequency band instead of using full duplex for multiple frequency bands, operating simultaneously. Although described as a dual-band embodiment, it will be apparent to those skilled in the art that the multiband coupling network 800 may be modified to implement virtually any number of frequency bands.

In contrast to the series RF switches in the multiband coupling network 700 of fig. 7, the RF switch 810 is configured to bypass operation such that the selected signal, when pulled low or biased low, turns on the RF switch 810. The coupled lines 820 and 840 are configured such that point a is 1/4 wavelengths from the radio frequency feed port 220 for both the low band and the high band.

Thus, if the RF switch 810 is open or off (high impedance to ground), the radio frequency feed port 220 "sees" a low impedance through the coupled lines 820 or 840 to the multiband antenna element 510, and the multiband antenna element 510 is turned on. If the RF switch 810 is closed or on (low impedance to ground), the radio frequency feed port 220 sees a high impedance and the multiband antenna element 510 is open. In other words, if the multiband antenna element 510 is DC biased low, at 1/4 wavelengths from the input of the coupled lines 820 and 840, the radio frequency feed port 220 sees open, so the multiband antenna element 510 is disconnected.

An advantage of the multiband coupling network 800 is less insertion loss because the RF switch 810 is not in the energy path from the radio frequency feed port 220 to the multiband antenna element 510. Further, because the RF switch 810 is not in the energy path from the radio frequency feed port 220 to the multiband antenna element 510, isolation may be improved compared to series RF switching. Isolation improvements may be particularly important in embodiments where the multiband communication apparatus 120 and the planar antenna apparatus 110 are capable of multiple-input multiple-output (MIMO) operation, as described in co-pending U.S. application No. 11/190,288 entitled "wireless systems having multiple antenna and multiple radios" filed on 26, 7/2005, which is incorporated herein by reference.

Another advantage of the multiband coupling network 800 is that only a single RF switch 810 is required to enable the multiband antenna element 510 for low band or high band operation. Further, in embodiments where a PIN diode is used as RF switch 810, the PIN diode has a stray capacitance of 0.17 pF. In the case where the RF switch 810 is not in the energy path from the radio frequency feed port 220 to the multiband antenna element 510, especially at frequencies above about 4-5GHz, matching problems may be reduced due to stray capacitance.

Although not shown, the RF switch of fig. 2-8 may be improved by placing one or more inductors in parallel with the RF switch, as described in co-pending U.S. patent application No. 11/413,670, filed on 28/4/2006, which is incorporated herein by reference.

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 become 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 following claims, which are intended to embrace all such alternatives, modifications, variations and equivalents as fall within the true spirit and scope of the invention.

Claims (25)

1. A multi-band antenna apparatus comprising:

a substrate having a first layer and a second layer;

a plurality of antenna elements on the first layer, each antenna element selectively coupled to a communication device, each antenna element configured to form a first portion of a first dipole having a directional radiation pattern polarized in a plane of the substrate, the first dipole configured to operate at a first radio frequency;

a ground component on a second layer of the substrate, the ground component forming a second portion of the first dipole, the second portion of the first dipole being asymmetric with respect to a plane of symmetry between a first portion and a second portion of the first dipole; and

a second dipole configured to radiate at a second radio frequency, the ground component comprising a respective portion of the second dipole.

2. The multiband antenna apparatus of claim 1, further comprising an antenna element selector coupled to the plurality of antenna elements, the antenna element selector configured to selectively couple the antenna elements to a communication device for generating the first and second radio frequencies.

3. The multiband antenna apparatus of claim 2, wherein the antenna element selector comprises a PIN diode network.

4. The multiband antenna apparatus of claim 3, wherein the plurality of antenna elements are configured to radiate with an omnidirectional radiation pattern when two or more of the antenna elements are coupled to the communication device.

5. The multiband antenna device of claim 2, wherein the antenna element selector is configured to simultaneously couple a first set of the plurality of antenna elements to the first radio frequency and a second set of the plurality of antenna elements to the second radio frequency.

6. The multiband antenna apparatus of claim 2, wherein a combined radiation pattern resulting from coupling two or more antenna elements to the communication device is more directional than a radiation pattern of a single antenna element.

7. The multiband antenna apparatus of claim 1, wherein the first radio frequency is in a range of 2.4 to 2.4835GHz and the second radio frequency is in a range of 4.9 to 5.825 GHz.

8. The multiband antenna device of claim 1, wherein the ground component comprises a reflector configured to concentrate a directional radiation pattern of the first dipole.

9. The multiband antenna device of claim 1, wherein the ground component comprises a reflector configured to broaden a frequency response of the first dipole.

10. The multiband antenna apparatus of claim 1, wherein the first and second dipoles comprise a dual-resonance structure.

11. The multiband antenna apparatus of claim 1, wherein the first portion of the first dipole and the second portion of the first dipole comprise arrow-shaped bent dipoles.

12. A system for implementing a multi-band antenna, comprising:

communication means for generating a low band RF or a high band RF;

first means for generating a first directional radiation pattern;

second means for generating a second directional radiation pattern; and

selecting means for receiving the low band RF or high band RF from the communication device and selectively coupling the first device or the second device to the communication device,

wherein the second directional radiation pattern is directionally offset from the first directional radiation pattern,

wherein the first means is for generating a first directional radiation pattern for the low band RF and the second means is for generating a second directional radiation pattern for the high band RF,

wherein the selecting means comprises means for simultaneously coupling the low band RF to the first means and the high band RF to the second means, and

wherein the first and second devices are antenna elements, respectively, and each antenna element comprises a first dipole element and a second dipole element.

13. The system of claim 12, wherein the first and second apparatuses form an omnidirectional radiation pattern when coupled to the communication apparatus.

14. The system of claim 12, further comprising means for expanding a directional radiation pattern of the first means.

15. The system of claim 12, further comprising means for concentrating the directional radiation pattern of the first means.

16. A method for implementing a multi-band antenna apparatus, comprising:

generating a first radio frequency signal in a communication device; and

coupling at least one of a plurality of co-planar antenna elements to the communication device to produce a directional radiation pattern in the plane of the antenna elements, wherein the plurality of co-planar antenna elements are configured to be coupled to the communication device to provide a plurality of different directional radiation patterns,

wherein each of the plurality of co-planar antenna elements comprises a co-planar antenna element and a ground component, wherein coupling at least one of the plurality of co-planar antenna elements to the communication device comprises enabling the co-planar antenna element and ground component to provide a plurality of directional radiation patterns, and wherein each of the plurality of co-planar antenna elements comprises a first dipole and a second dipole.

17. The method of claim 16, wherein the coplanar antenna element and ground component comprise a bent dipole.

18. The method of claim 16, further comprising coupling two or more of the plurality of co-planar antenna elements to the communication device to produce an omnidirectional radiation pattern.

19. The method of claim 16, further comprising concentrating the directional radiation pattern with one or more reflectors.

20. The method of claim 16, further comprising concentrating the directional radiation pattern with one or more Y-shaped reflectors.

21. The method of claim 16, further comprising concentrating the directional radiation pattern with one or more directors.

22. The method of claim 16, wherein coupling at least one of the plurality of coplanar antenna elements to the communication device comprises biasing a PIN diode.

23. The method of claim 16, further comprising coupling at least two of the plurality of co-planar antenna elements to the communication device to produce a more directional radiation pattern.

24. The method of claim 16, further comprising coupling at least two of the plurality of co-planar antenna elements to the communication device to produce a less directional radiation pattern.

25. The method of claim 16, further comprising coupling at least two of the plurality of co-planar antenna elements to the communication device to produce a radiation pattern that is directionally offset from an original radiation pattern.