(12) United States Patent
`(16) Patent N0.:
`US 6,486,832 B1
`
`Abramov et al.
`(:45) Date of Patent:
`Nov. 26, 2002
`
`IJSOO6486832B1
`
`(54) DIRECTION-AGILE ANTENNA SYSTEM
`FOR WIRELESS COMMUNICATIONS
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`(75)
`
`Inventors: Oleg Y. Abramov; Alexander G.
`’
`I
`’
`KashkarOV‘ AlexanderN Kirdin all
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`0f SLPCteerurgmU)
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`.
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`(73) ASSIgnee' AM GrouP’IrV1ne>CA(US)
`( * ) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154a,) by 0 days.
`
`4,881,081 A * 11/1989 Yoshihara ................... 342/359
`5,594,460 xx
`*
`1/1997 Eguchi u.”
`..u 343/765
`
`.........
`....342/359
`5,726,661 A *
`3/1998 Fuji
`9/2000 Jeon etaL .2
`.N. 343/711
`6,124,832 24
`*
`
`
`......
`6,229,480 B1 *
`5/2001 Shintani
`342/359
`.................... 343/359
`6,278,405 B1 *
`8/2001 Ha et a1.
`
`*
`
`’
`'t d b r
`c1 e
`3 examiner
`
`(21) Appl. NOJ 09/710,724
`
`(22)
`
`Filed:
`
`Nov. 10, 2000
`
`(51)
`(52)
`
`
`..... H01Q 1/36, H01Q 19/06
`.
`
`.
`............................... 343/700 MS; 343/754;
`343/766
`(58) Field of Search .......................... 343/700 MS, 765,
`343/766, 754, 757, 853, 872; 342/359,
`375
`
`Primary Examiner—Tan Ho
`(74) Attorney, Agent, or Firm—Leonard Tachner
`
`(57)
`
`ABSTRACT
`
`A direction-agile antenna system is implemented in a Wire-
`less network to allow Wireless communication devices to
`establish and maintain Wireless data links with each other.
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`US. Patent
`
`Nov. 26, 2002
`
`Sheet 1 0f 9
`
`US 6,486,832 B1
`
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`US. Patent
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`Nov. 26, 2002
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`US. Patent
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`Nov. 26, 2002
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`Sheet 6 0f 9
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`US 6,486,832 B1
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`US. Patent
`
`Nov. 26, 2002
`
`Sheet 8 0f 9
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`US 6,486,832 B1
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`
`
`SCANNING
`
`AN ANTENNA BEAM
`
`
`
`
`
`TRANSMITTING AT LEAST ONE POLLING REQUEST
`
`
`
`
`
`
`
`DETECTING A RESPONSE BY A
`SOURCE TO THE POLLING REQUEST
`
`DIRECTING THE ANTENNA BEAM
`
`TO THE SOURCE
`
`FIG. 9
`
`9
`
`

`

`US. Patent
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`Nov. 26, 2002
`
`Sheet 9 0f 9
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`US 6,486,832 B1
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`SCANNING AN ANTENNA BEAM OF THE
`ANTENNA OF A SLAVE DEVICE
`
`
`
`DETECTING A POLLING REQUEST
`
`BY A MASTER DEVICE
`
` DETERMINING A DESIRED DIRECTION
`
`OF THE ANTENNA BEAM
`
`
` DIRECTING THE ANTENNA BEAM
`
`
`TO THE MASTER DEVICE
`
`TRANSMITTING A RESPONSE TO
`
`THE MASTER DEVICE
`
`FIG.
`
`IO
`
`10
`
`10
`
`

`

`US 6,486,832 B1
`
`1
`DIRECTION-AGILE ANTENNA SYSTEM
`FOR WIRELESS COMMUNICATIONS
`
`10
`
`15
`
`’
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention relates to an antenna system, and
`more particularly, to an antenna system for communications
`in a wireless network.
`
`2. Background Art
`Omni-directional antennas have been implemented in
`various types of mobile communications devices in a con-
`ventional wireless network, for example, a digital mobile
`telephone network. In addition to voice communications,
`attempts have been made to provide high speed data com-
`munications between various types of apparatus including,
`for example, desktop computers, laptop computers, servers,
`peripherals and power management hubs in a wireless
`network. Compared to voice communications, data commu-
`nications typically require a large bandwidth, a very low bit
`error rate, and ability to communicate with multiple devices
`at different physical locations.
`To ensure high speed transmission of data at a very low
`bit error rate, a relatively high signal to noise ratio (SNR) at
`radio frequency (RF) is required to carry the data transmitted
`and received by the various apparatus in a conventional
`wireless network. Because of the spread of RF power over
`all directions in space by a typical omni-directional antenna
`in a conventional mobile wireless device, such as a mobile
`telephone, communications with such devices may occur
`only over relatively short distances. Furthermore, in a typi-
`cal mobile wireless network, the locations of at least some
`of the communications apparatus are not fixed with respect
`to each other, thereby further complicating the transmission
`and reception of data by different apparatus within the
`network.
`
`It is desirable that high speed data links be established in
`a mobile wireless network with a high degree of data
`integrity while obviating the need for high power RF trans-
`missions by mobile communications apparatus.
`Furthermore, it is desirable that high speed data links be
`maintained between different mobile communications appa-
`ratus in a wireless network even though the spatial locations
`of the apparatus may not be fixed with respect to each other.
`SUMMARY OF THE INVENTION
`
`40
`
`45
`
`The present invention provides a direction—agile antenna
`system for communications in a wireless network, generally
`comprising:
`an antenna capable of transmitting an electromagnetic
`signal in a direction having an antenna gain; and
`a controller connected to the antenna,
`the controller
`capable of generating a direction-selection signal to
`steer the electromagnetic signal to a selected direction
`corresponding to a high gain position in response to
`detecting an expected signal
`transmitted within the
`network.
`
`Advantageously, the direction-agile antenna system in an
`embodiment according to the present invention is capable of
`transmitting electromagnetic signals carrying digital data to
`an apparatus for which a transmission is intended with
`concentrated power density, thereby allowing a high rate of
`data transmission with a high degree of data integrity over
`a relatively long distance, while obviating the need for a
`high transmitted radio frequency (RF) power
`level.
`
`2
`the direction-agile antenna system in an
`Furthermore,
`embodiment according to the present invention allows dif-
`ferent apparatus to maintain instantaneous communications
`within a mobile wireless network even though the spatial
`positions of the apparatus may not be fixed with respect to
`each other.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The present invention will be described with particular
`embodiments thereof, and references will be made to the
`drawings in which:
`FIG. 1 is a partially cutaway perspective view of a
`direction-agile antenna system with mechanical beam steer-
`ing in an embodiment according to the present invention;
`FIG. 2A is a side-sectional view of the direction-agile
`antenna system of FIG. 1 obtained along sectional
`line
`2a—2a;
`FIG. 2B is another side-sectional view of the direction-
`
`agile antenna system of FIG. 1 obtained along sectional line
`2b—2b;
`FIG. 3 is a schematic block diagram showing an embodi-
`ment of a controller with digital signal processing for the
`direction-agile antenna system;
`FIG. 4 is a schematic block diagram showing an embodi-
`ment of an antenna control unit in a direction-agile antenna
`system with mechanical beam steering;
`FIG. 5 is a schematic representation of a mobile wireless
`network having a plurality of laptop computers equipped
`with direction-agile antenna systems in an embodiment
`according to the present invention;
`FIG. 6 shows a partially cutaway perspective view of a
`direction-agile antenna system with electronic beam steering
`in an embodiment according to the present invention;
`FIG. 7A is a side-sectional View of the direction-agile
`antenna system of FIG. 6 obtained along sectional
`line
`70—751 of FIG. 6;
`FIG. 7B is another side-sectional view of the direction-
`agile antenna system of FIG. 6 obtained along sectional line
`7b—7b of FIG. 6;
`FIG. 8 is a partially cutaway perspective view of a
`direction-agile antenna system with electronic beam steering
`in another embodiment according to the present invention;
`FIG. 9 is a flow chart illustrating a method of tracking a
`signal in a wireless network in an embodiment according to
`the present invention; and
`FIG. 10 is a flow chart illustrating a method of tracking a
`signal
`in a wireless network in an another embodiment
`according to the present invention.
`DETAILED DESCRIPTION
`
`FIG. 1 shows a partially cutaway perspective view of an
`embodiment of a direction-agile antenna system for use in a
`mobile wireless communications network.
`In this
`
`embodiment, the antenna system includes a mechanically
`steered antenna 12 enclosed within a dielectric cover 11. A
`
`60
`
`65
`
`motor driver 13 is connected to a motor 14 which is capable
`of rotating the antenna 12 to a desired direction. In an
`embodiment, the motor 14 is capable of rotating the antenna
`12 through 360° in azimuth to scan the antenna beam in a
`horizontal plane.
`In a further embodiment, the motor driver 13 is capable of
`driving the antenna 12 to scan in both azimuth and elevation.
`In an embodiment, the antenna 12 is a planar microstrip
`antenna which comprises a plurality of microstrip antenna
`
`11
`
`11
`
`

`

`US 6,486,832 B1
`
`3
`elements capable of transmitting and receiving electromag-
`netic signals in a direction having a positive antenna gain.
`Other types of directional antennas with positive antenna
`gains in desired directions may also be implemented in the
`direction-agile antenna system within the scope of the
`present invention. For example, parabolic reflector antennas,
`cassegrain antennas, waveguide slot array antennas and
`phased array antennas capable of producing directional
`electromagnetic beam patterns may be implemented in the
`direction-agile antenna system. Various types of conven-
`tional antennas can be designed to produce desired beam
`patterns in a conventional manner apparent to a person
`skilled in the art.
`FIGS. 2A and 2B show side-sectional Views of the
`
`direction-agile antenna system with a mechanically steered
`antenna of FIG. 1 obtained along sectional lines 2a—2a and
`2b—2b, respectively.
`FIG. 3 shows a block diagram of an embodiment of a
`controller for selecting the direction of electromagnetic
`transmission and reception by the antenna in the direction-
`agile antenna system. The controller 20 is capable of geri-
`erating a direction-selection signal to steer the electromag-
`netic signal
`transmitted by the antenna 12 to a selected
`direction corresponding to a high gain position, in response
`to detecting an expected signal transmitted within the wire-
`less communications network. In an embodiment, the con-
`troller 20 has a drivc signal output 22 conncctcd to a motor
`14in a mechanically steered direction-agile antenna system.
`Furthermore, the controller 20 has a radio frequency (RF)
`input 24 and an RF output 26 connected to the antenna 12.
`In an embodiment, the controller 20 comprises a trans-
`ceiver 40 and an antenna control unit 30. The transceiver 40,
`which is connected to the antenna 12 through the RF input
`24 and the RF output 26, is capable of generating an antenna
`gain signal
`in response to detecting an expected signal
`transmitted by another wireless device within the wireless
`communications network. The antenna gain signal generated
`by the transceiver 40 is transmitted to the antenna control
`unit 30, which generates a direction—selection signal to steer
`the antenna 12 to a desired direction in response to the
`antenna gain signal.
`the transceiver 40 comprises a
`In an embodiment,
`demodulator 41 connected to the RF input 24 to convert the
`received RF signal to a baseband signal. In an embodiment,
`the demodulator 41 converts the received RF signal to the
`baseband signal in multiple stages in a manner apparent to
`a person skilled in the art. For example, the RF signal may
`be first converted to an intermediate frequency (IF) signal
`and then demodulated into a baseband signal. To reduce the
`effect of noise spectrum in the received RF signal, a low
`noise amplifier (LNA) 48 is connected between the antenna
`12 and the demodulator 41 in an embodiment.
`
`In an embodiment, the transceiver 40 further comprises a
`baseband processor 42 connected to the demodulator 41 to
`generate the antenna gain signal which is transmitted to the
`antenna control unit 30. In an embodiment, the baseband
`processor 42 is capable of processing data transmitted and
`received by the direction-agile antenna system in addition to
`generating the antenna gain signal for steering the antenna
`beam to a desired direction to communicate with another
`wireless device within the wireless network.
`In this
`
`the data transmitted and received by the
`embodiment,
`direction-agile antenna system are transferred between the
`bascband proccssor 42 and a computcr 46, which is capablc
`of further transferring the data to peripherals through an
`interface, for example, a universal serial bus (USB) inter-
`face.
`
`10
`
`15
`
`,
`
`40
`
`45
`
`60
`
`65
`
`4
`In an embodiment, the transceiver 40 further comprises a
`modulator 44 connected to the baseband processor 42,
`which generates baseband signals carrying the data to be
`transmitted by the direction-agile antenna system to another
`wireless device within the wireless network. The modulator
`44 modulates the baseband signals generated by the base-
`band processor 42 to generate RF signals.
`In an
`embodiment, the RF signals generated by the modulator 44
`are amplified by a power amplifier 43, which is connected
`between the modulator 44 and the antenna 12. The demodu-
`lation of RF signals into baseband signals and the modula-
`tion of baseband signals into RF signals can be performed in
`a conventional manner apparent to a person skilled in the art.
`FIG. 4 shows a block diagram of an embodiment of an
`antenna control unit which is applicable to a direction-agile
`antenna system with a mechanically steered antenna. In this
`embodiment, the antenna control unit 30 comprises a digital
`signal processor (DSP) 32 which is connected to receive the
`antenna gain signal from the baseband processor 42 Via
`signal path 36. In an embodiment, the digital signal proces-
`sor 32 is also connected to flash and random access memory
`(RAM) 33. In an embodiment, the memory 33 stores appli-
`cation software which embeds the algorithm for generating
`a direction-selection signal
`for
`the antenna.
`In an
`embodiment, the digital signal processor 32 generates the
`direction-selection signal based upon the instant gain of the
`antenna in the desired direction,
`the instant angle of the
`antenna and the parameters of the driving motor.
`In an embodiment in which the direction-agile antenna is
`mechanically steered by a step motor, the antenna control
`unit 30 further comprises a step motor driver 38 connected
`between the digital signal processor 32 and the motor 14 for
`rotating the antenna 12. The motor 14 is capable of rotating
`the antenna 12 to the selected direction in response to the
`direction-selection signal received by the step motor driver
`38.
`In a further embodiment, a DC/DC regulator 31 is
`connected to the digital signal processor 32 and the motor
`14. In an embodiment, a feedback path 37 is provided
`between the antenna 12 and the digital signal processor 32
`to indicate the current angular position of the antenna to the
`processor 32, thereby allowing the processor 32 to track the
`movement of the antenna with better accuracy.
`FIG. 5 illustrates a mobile wireless network which
`
`includes a plurality of mobile wireless devices using
`direction-agile antennas. In FIG. 5, three laptop computers
`51, 52 and 53 are equipped with direction—agile antennas 65,
`66 and 67, respectively. One of the wireless communication
`devices which seeks to initiate a wireless data link is called
`a master device, whereas another wireless communication
`device which responds to the request to establish the data
`link is called a slave device. For example,
`the mobile
`wireless communication device 51 may be a master device
`which seeks to establish a wireless data link with either the
`wireless communication device 52 or the wireless commu-
`nication device 53.
`
`The direction-agile antenna 65 of the master device 51
`initially scans through successive angular positions such as
`those indicated by arrows 55, 56 and 57 until it arrives at a
`direction corresponding to the high gain position for a slave
`device with which a wireless data link is intended to be
`
`established. During the scanning of the direction-agile
`antenna 65, polling requests are transmitted repeatedly until
`the master device 51 receives a response to the polling
`request by one of the slave devices. If the slave device 52 is
`not thc onc intcndcd to cstablish a wirclcss data link with tho
`
`then the direction-agile
`master device 51, for example,
`antenna 66 of the slave device 52 does not
`transmit a
`response to the polling request.
`
`12
`
`12
`
`

`

`US 6,486,832 B1
`
`10
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`5
`On the other hand, if the slave device 53 is the one
`intended to establish a wireless data link with the master
`device 51, then the direction—agile antenna 67 of the slave
`device 53 is directed toward the direction-agile antenna 65
`of the master device 51, and a response is transmitted from
`the slave device 53 to the master device 51 to accomplish a
`handshake signifying the establishment of a wireless data
`link between the master device 51 and the slave device 53.
`
`When the response to the polling request is detected by
`the master device 51, the direction-agile antenna 65 of the
`master device 51 is directed toward the slave device 53, with
`an antenna beam pattern illustrated by the main lobe 58 of
`electromagnetic radiation generated by the antenna 65. In a
`similar manner, the direction-agile antenna 67 of the slave
`device 53 is directed toward the master device 51, with an
`antenna beam pattern illustrated by the main lobe 59 of
`electromagnetic radiation generated by the antenna 67.
`FIG. 6 shows an embodiment of a partially cutaway
`perspective view of a direction-agile antenna with electronic
`beam scanning. In this embodiment, the antenna need not be
`rotated mechanically to scan the antenna beam in all direc-
`tions. In the embodiment shown in FIG. 6, the electronically
`steered antenna comprises four antenna surfaces or planes to
`cover all azimuth angles, each of the antenna surfaces
`having a plurality of antenna elements capable of electroni-
`cally steering electromagnetic signals to a selected direction
`in response to the direction—selection signal generated by the
`antenna control unit 30. In an embodiment,
`the antenna
`elements on each surface comprise an array of microstrip
`radiators. In an embodiment, the circuitry of the antenna
`control unit 30 is integrated with one of the antenna surfaces
`on which the arrays of microstrip radiators are disposed. In
`FIG. 6, for example, four antenna planes are arranged at 90°
`to one another, with each of the antenna planes having two
`arrays of antenna elements, such as arrays 61 and 62.
`FIGS. 7A and 7B are side-sectional views of the elec-
`
`tronically steered direction-agile antenna of FIG. 6 obtained
`along sectional
`lines 7a—7a and 7b—7b,
`respectively.
`Power delivery lines 63 and 64 are provided to supply power
`to the antenna arrays such as antenna arrays 61 and 62 for
`transmitting electromagnetic signals.
`FIG. 8 shows another embodiment of a direction-agile
`antenna system with electronic beam steering. Three
`antenna surfaces 81, 82 and 83 are implemented to cover all
`azimuth angles. In the embodiment shown in FIG. 8, each
`antenna surface has two arrays of microstrip radiator ele-
`ments similar to the arrangement shown in FIGS. 6, 7A and
`7B and described above. In an embodiment in which a
`
`40
`
`45
`
`direction-agile antenna with electronic beam steering is
`implemented, at least some of the antenna elements are
`capable of being activated or switched on while other
`antenna elements are switched off,
`to allow the mobile
`wireless device to adjust the RF power level of transmitted
`electromagnetic signals.
`FIG. 9 shows a flow chart illustrating an embodiment of
`a method of tracking a signal in a wireless communications
`network by a master communications device using a
`direction-agile antenna system. The method generally com-
`prises the steps of scanning an antenna beam in multiple
`directions, transmitting at least one polling request during
`the step of scanning the antenna beam, detecting a response
`by a source within the wireless network to the polling
`request, and directing the antenna beam to the source. The
`source which transmits a response to the polling request is
`a slave device that is intended to establish a wireless data
`link with the master device. In an embodiment in which
`
`6
`mechanically steered direction-agile antennas are
`implemented, the antennas of the master and slave devices
`may rotate at different speeds and different angular incre—
`ments which are optimized to reduce the time for establish-
`ing a wireless data link.
`When the antenna of the master device is scanning over
`360° in azimuth, for example, polling requests are transmit-
`ted intermittently to seek a slave device which intends to
`establish a wireless data link with the master device. During
`the scanning of the direction-agile antenna of the master
`device,
`the transceiver of the master device awaits a
`response by a slave device within the network. The master
`device determines a desired direction of the antenna beam of
`
`the master device to the slave device by detecting a beam
`pattern of the RF signal carrying the response transmitted by
`the slave device and generating an antenna gain signal based
`upon the RF signal transmitted by the slave device.
`In an embodiment, the RF signal received by the master
`device is demodulated into an IF signal which is then
`converted into a baseband signal. The baseband signal is
`processed by a baseband processor to generate an antenna
`gain signal, which is in turn processed by the antenna control
`unit to generate a motor drive signal. In an embodiment in
`which a mechanically steered antenna is implemented, the
`antenna is rotated by a motor to the desired direction in
`response to the motor drive signal. Once the antenna beam
`of the master device is directed toward the slave device, the
`rotation of the antenna stops. In an embodiment, the position
`of the antenna is memorized by the antenna control unit of
`the master device while the master device starts to exchange
`data with the slave device.
`
`fine tuning is performed by the
`In an embodiment,
`direction-agile antenna system of the master device to
`maximize the gain of received RF signals as soon as the
`wireless data link is established between the master device
`and the slave device. Fine tuning of the antenna position is
`accomplished by slightly changing the direction of the
`antenna beam and measuring the strength of received RF
`signals.
`If the master device or the slave device is moving with
`respect to each other, the desired direction of the antenna
`beam of the master device may change over time. If the
`antenna control unit in the direction-agile antenna system of
`the master device determines that the strength of received
`RF signals is getting weaker, it drives the antenna to slightly
`different positions in an attempt to increase the strength of
`received RF signals. If the wireless data link is lost, the
`antenna beam is scanned in all directions until an RF signal
`from the slave device is detected to restore the wireless data
`link. In mobile wireless communications, the antenna beam
`may be scanned either continuously or in small steps in
`different directions to maintain the wireless data link
`
`between the master and slave devices, which may have
`constantly changing angular positions with respect to each
`other.
`
`The method of signal tracking in a wireless network is
`also applicable to embodiments in which at least some of the
`wireless communication devices in the network use elec-
`tronically steered direction-agile antennas instead of
`mechanically steered antennas for wireless data links.
`Instead of generating motor drive signals to rotate the
`antenna, the direction of the antenna beam is switched by
`selectively applying RF power to the most properly oriented
`antenna elements.
`
`60
`
`65
`
`In an embodiment, the direction of the antenna beam is
`changed by shifting the phases of RF signals transmitted by
`
`13
`
`13
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`

`

`US 6,486,832 B1
`
`8
`corresponding to a high gain position in response to
`detecting an expected signal
`transmitted within the
`network,
`wherein the antenna comprises a plurality of antenna
`elements capable of electronically steering the electro-
`magnetic signal to the selected direction in response to
`the direction-selection signal, and
`wherein the antenna elements are arranged in a plurality
`of arrays disposed on different planes.
`2. The system of claim 1, wherein the antenna elements
`are disposed on at least three planes to form an electronically
`steered radiation pattern.
`3. Adirection-agile antenna system for communication in
`a wireless network, comprising:
`an antenna capable of transmitting an electromagnetic
`signal in a direction having an antenna gain;
`a transceiver connected to the antenna, the transceiver
`capable of detecting an expected signal
`transmitted
`within the network and in response generating an
`antenna gain signal; and
`an antenna control unit connected to the transceiver, the
`antenna control unit capable of generating a direction-
`selection signal to steer the electromagnetic signal to a
`selected direction corresponding to a high gain position
`in response to the antenna gain signal,
`wherein the antenna comprises a plurality of antenna
`elements capable of electronically steering the electro-
`magnetic signal to the selected direction in response to
`the direction-selection signal, and
`wherein the antenna elements are arranged in a plurality
`of arrays disposed on different planes.
`4. The system of claim 3, wherein the antenna elements
`are disposed on at least three planes to form an electronically
`steered radiation pattern.
`5. Adirection-agile antenna system for communication in
`a wireless network, comprising:
`an antenna comprising a plurality of antenna elements
`capable of transmitting an electromagnetic signal in a
`selected direction;
`a transceiver connected to the antenna, the transceiver
`capable of detecting an expected signal
`transmitted
`within the network and in response generating an
`antenna gain signal; and
`an antenna control unit connected to the transceiver, the
`antenna control unit capable of generating a direction-
`selection signal
`to steer the electromagnetic signal
`electronically to the selected direction in response to
`the antenna gain signal,
`wherein the antenna elements are arranged in a plurality
`of arrays disposed on different planes.
`6. The system of claim 5, wherein the antenna elements
`are disposed on at least three planes to form an electronically
`steered radiation pattern.
`
`7
`different antenna eleme 1ts in a planar array using the prin-
`ciple of phased array radiation known to a person skilled in
`the art. Before a signal
`rom the slave device is detected by
`the master device, RF power is applied to the antenna arrays
`on all surfaces of the an enna of the master device to radiate
`polling requests in all directions. Once a response by a slave
`device is detected, one of the antenna surfaces of the master
`device is selected to
`ransmit RF signals in a selected
`direction at a desired power level. In a further embodiment,
`the power level of the transmitted RF signals is adjusted by
`activating only some 0 the antenna elements in the array
`while switching off other antenna elements.
`FIG. 10 shows a flow chart of an embodiment of a method
`
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`10
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`15
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`of tracking a signal wi hin a wireless network by a slave
`device. The method generally comprises the steps of scan—
`ning the antenna beam of the slave device in multiple
`directions, detecting a polling request by the master device,
`determining a desired direction of the antenna beam to the
`master device, directing the antenna beam to the master
`device, and transmitting a response to the master device. In '
`an embodiment, the desired direction of the antenna beam of
`the slave device is determined by detecting a beam pattern
`of an RF signal carrying the polling request by the master
`device and generating an antenna gain signal based upon the
`RF signal carrying the polling request. In an embodiment,
`the scanning and fine tuning of the antenna beam for the
`slave communication device is performed in a manner
`similar to that of the master device in a wireless network to
`establish and maintain a wireless data link.
`
`Direction-agile antennas with electronic beam scanning
`typically have very fast switching times, for example, on the
`order of about 50 ns. These antennas can be implemented in
`wireless devices serving as access points in a wireless local
`area network (WLAN), for example. Mechanically steered
`antennas with a rotating speed of about 120 rotations per
`minute, for example, can be implemented in mobile devices
`with relatively small dimensions. The transmission and
`reception of polling requests and responses to establish
`handshakes between master and slave communication
`
`devices in a wireless network may be performed using an
`industry-standard protocol according to IEEE 802.11, for
`example. Other types of protocols may also be used for
`establishing wireless data links between different wireless
`devices using direction-agile antenna systems within the
`scope of the present invention.
`The present invention has been described with respect to
`particular embodiments thereof, and numerous modifica-
`tions can be made which are within the scope of the
`invention as set forth in the claims.
`What is claimed is:
`1. Adirection-agile antenna system for communication in
`a wireless network, comprising:
`an antenna capable of transmitting an electromagnetic
`signal in a direction having an antenna gain; and
`a controller connected to the antenna,
`the controller
`capable of generating a direction-selection signal to
`steer the electromagnetic signal to a selected direction
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