United States Patent
`US 6,473,036 B2
`(10) Patent No.:
`(12)
`Proctor, Jr.
`(45) Date of Patent:
`Oct. 29, 2002
`
`
`US006473036B2
`
`(54) METHOD AND APPARATUS FOR ADAPTING
`ANTENNA ARRAY TO REDUCE
`ADAPTATION TIME WHILE INCREASING
`ARRAY PERFORMANCE
`
`(75)
`
`Inventor:
`
`James Arthur Proctor, Jr., Indialantic,
`FL (US)
`Lo
`.
`.
`(73) Assignee: Tantivy Communications, Inc.,
`Melbourne, FL (US)
`.
`.
`oo,
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`US.C. 154(b) by 0 days.
`
`.
`(*) Notice:
`
`4,516,126 A *
`5/1985 Masak et al. oo... 343/383
`4,631,546 A
`12/1986 Dumasetal.
`tenn, A . tologs wane
`349/178
`>
`>
`ODSONL ..sscceeseseceseeeeees
`4,872,016 A * 10/1989 Kress... 342/380
`(List continued on nextpage.)
`
`OTHER PUBLICATIONS
`
`Harrington “Reactively Controlled Antenna Arrays” Dept.
`of Electrical and Computer Engineering, Syracuse Univer-
`sity, Syracuse NY 13210 pp. 62-65.
`
`(List continued on next page.)
`
`(21) Appl. No.: 09/776,558
`oa.
`Filed:
`(22)
`Feb. 2, 2001
`(65)
`Prior Publication Data
`US 2001/0020915 Al Sep. 13, 2001
`
`Related U.S. Application Data
`
`of application
`
`No.
`
`,117,
`
`filed on
`
`Dec.11,
`
`, NOW
`
`t
`
`itt
`
`i
`
`t.T
`
`ight
`
`Primary Examiner—Dao Phan
`(74) Attorney, Agent, or Firm—John L. DeAngelis, Jr;
`Beusse Brownlee Bowdoin & Wolter, P.A.
`(57)
`ABSTRACT
`oo.
`.
`An antenna apparatus that can increase capacity in a cellular
`communication system is disclosed. The antenna operates in
`conjunction with a mobile subscriber unit and comprises a
`plurality of antenna elements, each coupled to a respective
`(63) Continuation-in-part of application No. 09/579,084,filed on
`weight com component 0providea weight to the Signal
`May 25, 2000,nowSot6.304215,whichis&division
`foreach.
`lenme (or reat..
`y) «te‘d k ooh
`° vias
`Pat. No. 6,100,843, which is a continuation of application
`or each
`antenna element
`1s adjusted
`to achieve opuimum
`No. 09/157,736,filed on Sep. 21, 1998, now abandoned.
`reception during, for example, an idle mode whenapilot
`7
`signal is received. The antenna array creates a beam former
`for signals to be transmitted from the mobile subscriber unit,
`and a directional receiving array to more optimally detect
`and receive signals transmitted from the base station. By
`directionally receiving and transmitting signals, multipath
`fading and intercell interference are greatly reduced. The
`weights are adjusted in a coarse and a fine mode. In the
`coarse mode all the weight control components are jointly
`adjusted or changed so that the antenna beam scans through
`a predetermined sector of a circle until a signal quality
`metric of the received signal
`is optimized. The coarse
`adjustment mode is followed by a fine adjustment mode
`during which the weights of are independently adjusted to
`further optimize the signal quality metric.
`
`(51)
`Int. Cl.
`See eee eweeneee seenseen eee eeeee seesseen eee eees H01Q 3/24
`
`(52)
`:
`.. 342/372, 342/373
`(58) Field of Search 0.0.0.0... eee 342/367, 368,
`342/372, 373; 455/422, 426
`.
`References Cited
`U.S. PATENT DOCUMENTS
`
`(56)
`
`2/1971 Himmelet al.
`3,560,978 A
`4/1973 Blacketal.
`3,725,938 A
`3,766,559 A * 10/1973 Butcheretal. ....... 343/100 SA
`3,846,799 A
`11/1974 Gueguen
`3,950,753 A
`4/1976 Chisholm
`4,236,158 A * 11/1980 Daniel... 343/100 LE
`4,260,994 A
`4/1981 Parker
`4,387,378 A
`6/1983 Henderson
`
`42 Claims, 5 Drawing Sheets
`
`
`
`100
`
`«170
`4
`
`,
`
`
`
`Ut | pee 12|pee t13|pe 4|pet t8 420
`
`[a pt p
`pla,
`p
`Q
`
`
`
`
`
`
`
`
`
`
`
`fs
`fs
`fs
`fs
`fs
`TT
`
`180
`170be
`
`[01
`.
`480
`179
`104 180
`a,
`
`
`
`
`
`
`
`\435 & oT140
`
`
`180
`
`110
`
`APPLE ETAL. 1028
`
`APPLE ET AL. 1028
`
`1
`
`

`

`US 6,473,036 B2
`
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`Preston et al “Size Reduction of Switched Parasitic Direc-
`
`6/1993 Minamisono............... 342/383
`5,218,359 A *
`8/1993 Audrenetal.
`5,235,343 A
`3/1994 Sanford et al.
`5,294,939 A
`4/1996 Applebaum .............. 342/162
`5,510,796 A *
`4/1997 Prater
`5,617,102 A
`6/1998 Pritchett
`5,767,807 A
`5/1999 Taenzer
`5,905,473 A
`3/2000 Thieletal.
`6,034,638 A
`3/2000 Koscicaet al.
`6,037,905 A
`8/2000 Proctor, Jr. et al.
`6,100,843 A
`9/2000 Upadhyayetal. .......... 375/144
`6,115,409 A *
`OTHER PUBLICATIONS
`
`Luzwick et al “A reactively Loaded Aperture Antenna
`Array” IEEE Transactions on Antennas and Propagation,
`vol. AP-26, No. 4, Jul. 1978 pp. 543-547.
`Milne “A Small Adaptive Array Antenna For Mobile Com-
`munications”, CH2128—7/85/0000-0797$01.00 IEEE pp.
`797-800.
`
`Sibille “Circular Switched Monopole Arrays For Beam
`Steering Wireless Communications”, Electronics Letters,
`27” Mar. 1997 vol. 33 No. 7 pp. 551, 552.
`Chelouah “Angular Diversity Based on Beam Switching of
`Circular Arrays for HIPERLAN Terminals”, Electronic Let-
`ters, 2” Mar. 2000 vol. 36 No. 5 pp. 387, 388.
`Vaughan “Switched Parasitic Elements for Antenna Diver-
`sity”, IEEE Transactions on Antennas and Propagation,vol.
`47, No. 2 Feb. 1999 pp. 399-405.
`Harrington “Reactively Controller Directive Arrays”, IEEE
`Transactions on Antennas and Propagation, vol. AP-26 No.
`3 May 1978 pp. 390-395.
`James et al “Electrically Short Monopole Antennas With
`Dielectric or Ferrite Coatings”, Proc. IEEE vol. 125 No. 9
`Sep. 1978 pp. 793-803.
`Scott et al “Diversity Gain from a Single—Port Adaptive
`Antenna Using Switched Parasitic Elements Illustrated with
`a Wife and Monopole Prototype”, IEEE Transactions on
`Antennas and Propagation, vol. 47 No. 6 Jun. 1999 pp.
`1066-1070.
`
`Preston et al “Base-Station Tracking in Mobile Communi-
`cations Using a Switched Parasitic Antenna Array”, IEEE
`Transactions on Antennas and Propagation, vol. 46 No. 6
`Jun. 1998 pp. 841-844.
`Preston et al “Electronic Beam Steering Using Switched
`Parasitic Patch Elements”, Electronic Letters 2”? Jan. 1997
`vol. 33 No. 1 pp. 7,8.
`Preston et al “Systematic Approach to the Design of Direc-
`tional Antennas Using Switched Parasitic and Switched
`Active Elements”, 1998 Asia—Pacific Microwave Confer-
`ence pp. 531-534.
`
`tional Antennas Using General Algorithm Optimisation
`Techniques”, 1998 Asia—Pacific Microwave Conference pp.
`1401-1404.
`
`Preston et al A Multibeam Antenna Using Switched Parasitic
`and Switched Active Elements for Space—Division Mulitple
`Access Applications IEICE Trans., Electron., vol. E82—C
`No. 7 Jul. 1999 pp. 1202-1210.
`Matsumoto “Gradients of a Performance Index Arising from
`Network Optimisation in the Frequency Domain”, Electron-
`ics Letters 27” Jun. 1974 vol. 10 No. 13 pp. 263-265.
`Knight
`“Low-Frequency Behaviour of
`the Beverage
`Aerial”, Electronics Letters 6” Jan. 1977 vol. 13 No. 1 pp.
`21, 22.
`King “The Many Faces of the Insulate Antenna”, Proceed-
`ings of the IEEE, vol. 64 No. 2 Feb. 1976 pp. 228-238.
`Long et al “The Resonant Cylindrical Dielectric Cavity
`Antenna”, IEEE Transactions on Antennas and Propagation
`vol. AP-31 No. 3 May 1983 pp. 406-412.
`Mc Allister et al “Resonant Hemispherical Dielectric
`Antenna”, Electronics Letters 2”“ Aug. 1984 Vo.20 No. 16.
`Lu et al “Multibeam Switched Parasitic Antenna Embed-
`ded in Dielectric for Wireless Communications Systems”,
`Electronics Letters 5Jul. 2001 vol. 37 No. 14 pp. 871, 872.
`Mc Allister
`et
`al
`“Rectangular Dielectric Resonator
`Antenna”, Electronics Letters 17 Mar. 1983 vol. 19 No. 6
`pp. 218, 219.
`Kingsley et al “Beam Steering and Monopulse Processing of
`Probe—fed Dielectric Resonator Antennas”, IEEE Proc.—jRa-
`dar, Sonar Navig., vol. 146 No. 3 Jun. 1999 pp. 121-125.
`Giger “Low—Angle Microwave Propagation: Physics and
`Modeling” 1991 Artech House, Inc. 685 Canton St., Nor-
`wood, MA 02062 Intl. Standard Book No. 0-89006-584—5
`Library of Congress Catalog Card No. 91-20581.
`in a
`Ruze “Contributions: Lateral-Feed Displacement
`Paraboloid”, IEEE Transactions on Antennas and Propaga-
`tion Sep. 1965 pp. 660-665.
`Durnan “Switched Parasitic Feeds for Parabolic Antenna
`
`Angle Diversity”, School of Microelectronic Engineering,
`Gniffith University, Brisbane Qld.4111, Australia.
`Durnan “Optimization of Microwave Parabolic Antenna
`Systems Using Switched Parasitic Feed Structures”, School
`of Microelectronic Engineering, Griffith University, Bris-
`bane Qld.4111, Australia.
`Preston “Direction Finding Using a Switched Parasitic
`Antenna Array”, 0-7803-4178-/3/97/$10.00 1997 IEEE pp.
`1024-1027.
`
`* cited by examiner
`
`2
`
`

`

`U.S. Patent
`
`Oct. 29, 2002
`
`Sheet 1 of 5
`
`US 6,473,036 B2
`
`
`
`3
`
`

`

`U.S. Patent
`
`O91
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`(10d)LF061aOh
`
`OL081
`
`08!081
`
`Oct. 29, 2002
`
`Sheet 2 of 5
`
`US 6,473,036 B2
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`

`U.S. Patent
`
`Oct. 29, 2002
`
`Sheet 3 of 5
`
`US 6,473,036 B2
`
`
`
`ENTER IDLE MODE |30
`
`2
`
`SET WEIGHT VALUES |39
`
`
`
`3
`
`304
`
`9
`
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`“MEASUREPILOT SIGNAL
`METRIC: SAVE RESULT
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`BY NEXTSETTING
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`305
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`306
`L DETERMINE BEST SETTING
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`4FIG. 3 [corFINEADUPROCESS|39g
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`BEST METRIC
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`
`5
`
`

`

`U.S. Patent
`
`Oct. 29, 2002
`
`Sheet 4 of 5
`
`US 6,473,036 B2
`
`SELECT ONE WEIGHT
`CONTROL COMPONENT
`
`~~ADJUST OTHER WEIGHT
`SETTINGS
`
`“MEASURE SIGNAL QUALITY
`
`METRIC AND SAVE RESULT
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`r
`
`DONE ve
`
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`
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`
`DONE s
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`DETERMINE OPTIMUM
`SETTING
`
`SET WEIGHTS FOR
`OPTIMUMMETRIC
`
`
`
`FIG. 4
`
`401
`
`402
`
`406
`
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`
`414
`
`6
`
`

`

`U.S. Patent
`
`Oct. 29, 2002
`
`Sheet 5 of 5
`
`US 6,473,036 B2
`
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`

`US 6,473,036 B2
`
`1
`METHOD AND APPARATUS FOR ADAPTING
`ANTENNA ARRAY TO REDUCE
`ADAPTATION TIME WHILE INCREASING
`ARRAY PERFORMANCE
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application is a Continuation-In-Part of U.S. patent
`application Ser. No. 09/579,084 filed May 25, 2000 entitled
`“Adaptive Antenna For Use In Same Frequency Networks,”
`now USS. Pat. No. 6,304,215, which is a divisional appli-
`cation Ser. No. 09/210,117 filed Dec. 11, 1998 of Issued U.S.
`Pat. No. 6,100,843 entitled “Adaptive Antenna for use in
`Same Frequency Networks,” which is a continuation appli-
`cation of U.S. patent application Ser. No. 09/157,736 filed
`Sep. 21, 1998 now abn. entitled “Method and Apparatus
`Providing an Adaptive Antenna For Use in Same Frequency
`Networks,” the entire teachings of which are incorporated
`herein by reference.
`
`FIELD OF THE INVENTION
`
`This invention relates to mobile (or portable) cellular
`communication systems, and moreparticularly to an antenna
`apparatus for use by mobile subscriber units to provide beam
`forming transmission and reception capabilities.
`
`BACKGROUND OF THE INVENTION
`
`Code division multiple access (CDMA) communication
`systems provide wireless communications between a base
`station and one or more mobile subscriber units. The base
`
`station is typically a computer controlled set of transceivers
`that are interconnected to a land-based public switched
`telephone network (PSTN). The base station includes an
`antenna apparatus for sending forward link radio frequency
`signals to the mobile subscriber units. The base station
`antenna also receives reverse link radio frequency signals
`transmitted from each mobile unit. Each mobile subscriber
`
`unit also contains an antenna apparatus for the reception of
`the forward link signals and for transmission of the reverse
`links signals. A typical mobile subscriber unit is a digital
`cellular telephone handsetor a personal computer coupled to
`a cellular modem. In CDMAcellular systems, multiple
`mobile subscriber units may transmit and receive signals on
`the same frequency, but with different modulation codes, to
`distinguish signals sent to or received from individual sub-
`scriber units.
`
`The most common type of antenna for transmitting and
`receiving signals at a mobile subscriber unit is a monopole
`or omnidirectional antenna. This type of antenna consists of
`a single wire or antenna element
`that
`is coupled to a
`transceiver within the subscriber unit. The transceiver
`
`receives reverse link signals to be transmitted from circuitry
`within the subscriber unit and modulates the signals onto a
`carrier signal at a specific frequency assigned to that sub-
`scriber unit. The modulated carrier signal is transmitted by
`the antenna element. Forward link signals received by the
`antenna elementat a specific frequency are demodulated by
`the transceiver and supplied to processing circuitry within
`the subscriber unit.
`
`The signal transmitted from a monopole antennais omni-
`directional in nature. Thatis, the signalis sent with the same
`signal strength in all directions in a generally horizontal
`plane. Reception of a signal with a monopole antenna
`element is likewise omnidirectional. A monopole antenna
`does not differentiate in its ability to detect a signal in one
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`direction versus detection of the same or a different signal
`coming from another direction. Generally, a monopole
`antenna doesnot produce significant radiation in the azimuth
`direction. The antenna pattern is commonly referred to as a
`donut shape with the antenna elementlocated at the center
`of the donut hole.
`
`A second type of antenna that may be used by mobile
`subscriber units is described in U.S. Pat. No. 5,617,102. The
`system described therein provides a directional antenna
`comprising two antenna elements mounted onthe outer case
`of a laptop computer, for example. The system includes a
`phase shifter attached to each element. The phase shifter
`may be switched on or off to effect the phase of signals
`transmitted or received during communications to and from
`the computer. By switching the phase shifters on and regu-
`lating the amount of phase shift imparted to the signals input
`thereto,
`the antenna pattern (which applies to both the
`receive and transmit modes) may be modified to provide a
`concentrated signal or beam in the selected direction. This is
`referred to as an increase in antenna gain or directionality.
`The dual element antennaof the cited patent thereby directs
`the transmitted signal into predetermined quadrantsor direc-
`tions to allow for changes in orientation of the subscriber
`unit relative to the base station, while minimizing signal loss
`due to the orientation change.
`In accordance with the
`antenna reciprocity theorem, the antenna receive character-
`istics are similarly effected by the use of the phase shifters.
`CDMAcellular systems are also recognized as being
`interference limited systems. That is, as more mobile sub-
`scriber units become active in a cell and in adjacentcells,
`frequency interference becomes greater and thus error rates
`increase. As error rates increase,
`to maintain signal and
`system integrity, the operator must decrease the maximum
`data rates allowable. Thus, another method by which data
`rate can be increased in a CDMAsystem is to decrease the
`numberof active mobile subscriber units, thus clearing the
`airwavesof potential interference. For instance, to increase
`the maximum available data rate by a factor of two, the
`number of active mobile subscriber units can be decreased
`
`by one half. However, this is rarely an effective mechanism
`to increase data rates due to the lack of priority assignments
`to the system users.
`
`SUMMARYOF THE INVENTION
`
`Problemsof the Prior Art
`
`Various problemsare inherent in prior art antennas used
`on mobile subscriber units in wireless communications
`
`systems. One such problem is called multipath fading. In
`multipath fading, a radio frequency signal transmitted from
`a sender(either a basestation or mobile subscriber unit) may
`encounter interference on route to the intended receiver. The
`
`signal may, for example, be reflected from objects, such as
`buildings that are not in the direct path of transmission, but
`that redirect a reflected version of the original signal to the
`receiver. In such instances, the receiver receives two ver-
`sions of the same radio signal; the original version and a
`reflected version. Each received signal
`is at
`the same
`frequency, but the reflected signal may be out of phase with
`the original due to the reflection and consequent longer
`transmission path. As a result,
`the original and reflected
`signals may partially cancel each other out (destructive
`interference), resulting in fading or dropoutsin the received
`signal, hence the term multipath fading.
`Single element antennas are highly susceptible to multi-
`path fading. A single element antenna has no way of
`
`8
`
`8
`
`

`

`US 6,473,036 B2
`
`3
`determining the direction from which a transmitted signalis
`sent and cannot be tuned or attenuated to more accurately
`detect and receive a signal in any particular direction. Its
`directional pattern is fixed by the physical structure of the
`antenna components.
`The dual element antenna described in the aforemen-
`tioned reference is also susceptible to multipath fading, due
`to the symmetrical and opposing nature of the hemispherical
`lobes formed by the antenna pattern when the phase shifter
`is activated. Since the lobes created in the antenna pattern
`are more or less symmetrical and opposite from one another,
`a signal reflected in a reverse direction from its origin can be
`received with as much poweras the original signal that is
`received directly. That is, if the original signal reflects from
`an object beyond or behind the intended receiver (with
`respect to the sender) and reflects back at the intended
`receiver from the opposite direction as the directly received
`signal, a phase difference in the two signals can create
`destructive interference due to multipath fading.
`Another problem present in cellular communication sys-
`tems is inter-cell interference. Most cellular systems are
`divided into individual cells, with each cell having a base
`station located at its center. The placement of each base
`station is arranged such that neighboring base stations are
`located at approximately sixty degree intervals from each
`other. In essence, each cell may be viewed as a six sided
`polygon with a base station at the center. The edges of each
`cell adjoin each other and a group of cells form a
`honeycomb-like imageif each cell edge were to be drawn as
`a line and all cells were viewed from above. The distance
`
`from the edge of a cell to its base station is typically driven
`by the maximum amount of powerthat is to be required to
`transmit an acceptable signal from a mobile subscriber unit
`located near the edge of the cell to that cell’s base station
`(i.e., the power required to transmit an acceptable signal a
`distance equal to the radius of onecell).
`Intercell interference occurs when a mobile subscriber
`
`unit near the edge of one cell transmits a signal that crosses
`over the edge into a neighboring cell and interferes with
`communications taking place within the neighboring cell.
`Typically,
`intercell interference occurs when similar fre-
`quencies are used for communications in neighboringcells.
`The problem ofintercell interference is compounded by the
`fact that subscriber units near the edges of a cell typically
`use higher transmit powers so that the signals they transmit
`can be effectively received by the intended base station
`located at
`the cell center. Consider that the signal from
`another mobile subscriber unit located beyond or behind the
`intended receiver may be arrive at the base station at the
`same powerlevel, representing additional interference.
`The intercell
`interference problem is exacerbated in
`CDMAsystems,since the subscriber units in adjacent cells
`may typically be transmitting on the same frequency. For
`example, generally, two subscriber units in adjacent cells
`operating at the same carrier frequency but transmitting to
`different base stations will interfere with each other if both
`
`signals are received at one of the base stations. One signal
`appears as noise relative to the other. The degree of inter-
`ference and the receiver’s ability to detect and demodulate
`the intended signal is also influenced by the powerlevelat
`which the subscriber units are operating. If one of the
`subscriber units is situated at the edge of a cell, it transmits
`at a higher powerlevel, relative to other units within its cell
`and the adjacentcell, to reach the intended basestation. But,
`its signal is also received by the unintended basestation,1.e.,
`the base station in the adjacent cell. Depending on the
`relative power level of two same-carrier frequency signals
`
`4
`received at the unintended basestation, it may not be able to
`properly identify a signal transmitted from within its cell
`from the signal transmitted from the adjacent cell. What is
`needed is a way to reduce the subscriber unit antenna’s
`apparentfield of view, which can have a markedeffect on the
`operation of the forward link (base to subscriber) by reduc-
`ing the apparent number of interfering transmissions
`received at a base station. A similar improvementis needed
`for the reverse link, so that the transmitted signal power
`needed to achieve a particular receive signal quality can be
`reduced.
`
`BRIEF DESCRIPTION OF THE PRESENT
`INVENTION
`
`The present invention provides an inexpensive antenna
`apparatus for use with a mobile or portable subscriber unit
`in a wireless same-frequency communications system, such
`as a CDMAcellular communications system.
`The invention provides a mechanism and method for
`efficiently configuring the antenna apparatus to maximize
`the effective radiated and/or received energy. The antenna
`apparatus includes multiple antenna elements and a like
`numberof adjustable weight control components. As is well
`known in the art, the weight control components are con-
`trollable to adjust the phase, amplitude and/or delay of the
`signal coupled to each of the antenna elements. The weight
`control components (e.g., phase shifter, delay line, amplifier
`with variable gain) are jointly and independently operable to
`affect the direction of reverse link signals transmitted from
`the subscriber unit on each of the antenna elements and the
`
`direction of forward link signals transmitted from the sub-
`scriber unit.
`
`The antenna controller provides a coarse and a fine
`adjustment for the weight control components. First, the
`controller jointly controls each of the weight control com-
`ponentsto effect the phase of the signal input to each of the
`antenna elements so that the antenna is pointed generally in
`a given direction. The controller then shifts to an indepen-
`dent mode where each of the weight control components is
`independently adjusted to fine tune the antenna pointing
`direction. The proper adjustment of the weight control
`components in the independent mode can, for example, be
`determined by monitoring an optimum responseto a pilot
`signal transmitted from the base station and received by the
`subscriber unit when operative in anidle state (i.e., during
`which no information or payload data is being transmitted
`from or received by the subscriber unit). The antenna
`apparatus thus acts as a beam former for transmission of
`signals from the subscriber unit and acts as a directional
`antenna for signals received by the subscriber unit.
`Through the use of an array of antenna elements, each
`having a programmable weight control componentfor form-
`ing the antenna beam as desired,
`the antenna apparatus
`increases the effective transmit power per bit transmitted.
`Thus, the numberof active subscriber units in a cell may
`remain the same while the antenna apparatus of this inven-
`tion increases data rates for each subscriber unit beyond
`those achievable by prior art antennas. Alternatively, if data
`rates are maintained at a given rate, more subscriber units
`may becomesimultaneously active in a single cell using the
`antenna apparatus described herein.
`In either case,
`the
`capacity of a cell is increased, as measured by the sum total
`of data being communicated at any given time.
`Forward link communications capacity can be increased
`as well, due to the directional reception capabilities of the
`antenna apparatus. Since the antenna apparatusis less sus-
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`5
`ceptible to interference from adjacent cells, the forward link
`system capacity can be increased by adding more users or by
`increasing cell radius size.
`subscriber units 60 in a cell 50 by way of example only and
`implementation of the
`With respect
`to the physical
`for ease of description of the invention. The invention is
`antenna apparatus, one embodimentof the invention speci-
`applicable to systems in which there are typically many
`fies that first, second, and third antenna elements are posi-
`more subscriber units communicating with one or more base
`tioned at locations corresponding to corners of an equilateral
`stations in an individual cell, such as the cell 50.
`triangle and are aligned orthogonal to a plane defined by the
`triangle. Another embodiment specifies that first, second,
`It is also to be understood by those skilled in the art that
`10
`third, and fourth antenna elements are positioned at loca-
`FIG. 1 may beastandard cellular type communications
`tions corresponding to the corners of a rectangle or square,
`system employing signaling schemes such as a CDMA,
`with a fifth antenna element positioned at a location corre-
`TDMA, GSM or others in which the radio channels are
`sponding to the approximate center of the rectangle or
`assigned to carry data and/or voice betweenthe base stations
`square.
`104 and subscriber units 60. In a preferred embodiment,
`FIG. 1 is a CDMA-like system, using code division multi-
`plexing principles such as those defined in the IS-95B
`standards for the air interface.
`
`US 6,473,036 B2
`
`6
`from the basestation of the exiting cell to the base station of
`the entering cell.
`FIG. 1 illustrates one base station 160 and three mobile
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`15
`
`The foregoing and other objects, features and advantages
`of the invention will be apparent from the following more
`particular description of preferred embodiments of the
`invention, as illustrated in the accompanying drawings in
`which like reference characters refer to the same parts
`throughout the different views. The drawings are not nec-
`essarily to scale, emphasis instead being placed upon illus-
`trating the principles of the invention.
`FIG. 1 illustrates a cell of a CDMAcellular communica-
`tions system.
`FIG. 2 illustrates a preferred configuration of an antenna
`apparatus used by a mobile subscriber unit in a cellular
`system according to this invention.
`FIG. 3 is a flow chart of the processing steps performed
`to optimally set the weight value for the signal transmitted
`from or received by each antenna element.
`FIG. 4 is a flow chart of steps performed by a perturba-
`tional algorithm to optimally determine the arrangement of
`antenna elements.
`
`The invention provides the mobile subscriber units 60
`with an antenna 100 that provides directional reception of
`forward link radio signals transmitted from the base station
`160, as well as directional
`transmission of reverse link
`signals, via a process called beam forming, from the mobile
`subscriber units 60 to the base station 160. This concept is
`illustrated in FIG. 1 by the example beam patterns 71
`through 73 that extend outwardly from each mobile sub-
`scriber unit 60 moreorless in a direction for best propaga-
`tion toward the base station 160. By being able to direct
`transmission more or less toward the base station 160, and
`by being able to directively receive signals originating more
`or less from the location of the base station 160, the antenna
`apparatus 100 reduces the effects of intercell interference
`and multipath fading for the mobile subscriber units 60.
`Moreover, since the transmission beam patterns 71, 72 and
`73 extend outwardin the direction of the base station 160 but
`are attenuated in most other directions,
`less power
`is
`required for transmission of effective communications sig-
`nals from the mobile subscriber units 60-1, 60-2 and 60-3 to
`the base station 160.
`FIG. 2 illustrates a detailed isometric view of a mobile
`subscriber unit 60 and an associated antenna apparatus 100
`configured according to one embodiment of the present
`invention. Antenna apparatus 100 includes a platform or
`housing 110 upon which are mounted five antenna elements
`101 through 105. Within housing 110, the antenna apparatus
`100 includes weight control components 111 through 115 for
`adjusting the amplitude, phase or both the amplitude and
`phase of the signal received by or transmitted from each
`element 101 through 105, a bi-directional summation net-
`work or splitter/combiner 120, a transceiver 130, and a
`controller 140, which are all interconnected via a bus 135.
`As illustrated, the antenna apparatus 100 is coupled via the
`transceiver 130 to a laptop computer 150 (not drawn to
`scale). The antenna 100 allows the laptop computer 150 to
`perform wireless data communications via forward link
`signals 180 transmitted from the base station 160 and
`reverse link signals 170 transmitted to the base station 160.
`In one embodiment, each antenna element 101 through
`105 is disposed on the surface of the housing 110 as
`illustrated in FIG. 2. Here, four elements 101, 102, 104 and
`over any number of different available communications
`105 are respectively positioned at locations correspondingto
`protocols such as primary rate ISDN, or other LAPD based
`the corners of a rectangle (in one embodimentthe rectangle
`protocols such as IS-634 or V5.2, or even TCP/IP if network
`is a square), andafifth antenna element 103is positioned at
`75 is a packet based Ethernet network such as the Internet.
`The subscriber units 60 may be mobile in nature and may
`a location corresponding to the center of the rectangle. The
`travel from one location to another while communicating
`distance between each element 101 through 105 is great
`with the base station 160. As the subscriber units leave one
`enoughso that the relationship between a signal received by
`cell and enter another, the communicationslink is handed off
`more than one element 101 through 105 will be out of phase
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`FIG. 5 illustrates flow diagram for a perturbational com-
`putational algorithm for computing the weights to be
`assigned to each antenna element.
`FIG. 6 illustrates another antenna embodiment to which
`
`the teachings of the present invention can be applied.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`FIG. 1 illustrates one cell 50 of a typical CDMAcellular
`communication system. The cell 50 represents a geographi-
`cal area in which mobile subscriber units 60-1 through 60-3
`communicate with a centrally located base station 160. Each
`subscriber unit 60 is equipped with an antenna 100 config-
`ured according to the present invention. The subscriber units
`60 are provided with wireless data and/or voice services by
`the system operator and can connect devices such as, for
`example, laptop computers, portable computers, personal
`digital assistants (PDAs)orthelike through basestation 160
`to a network 75, which can be the public switched telephone
`network (PSTN), a packet switched computer network, such
`as the Internet, a public data network or a private intranet.
`The base station 160 can communicate with the network 75
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`US 6,473,036 B2
`
`7
`with other elements that also receive the same signal,
`assuming all elements 101 through 105 have the same
`setting for their respective weight control components 111
`through 115.
`However, accordingto the operation of the antenna 100 in
`this invention, the weight control components 111 through
`115 are both dependently and independently adjustable to
`affect the directionality of signals to be transmitted and/or
`received to or from the subscriber unit (i.e., laptop computer
`150 in this example). By properly adjusting the weight
`control components (i.e., the weights) for each element 101
`through 105 during signal transmission, a composite beam is
`formed that is positionally directed toward the base station
`160. Thatis, the optimal arrangement for the weight control
`components for sending a reverse link signal 170 from the
`antenna 100 is a setting for each antenna element 101
`through 105 that creates a directional reverse link signal
`beam former. The result is an antenna 100 that directs a
`
`stronger reverse link signal pattern in the direction of the
`intended receiver base station 160, reducing the likelihood
`that an unintended base station in an adjacent cell will also
`receive the reverse link signal 170.
`The weight control componentsettings used for transmis-
`sion of signals over the reverse link 170 also cause the
`elements 101 to 105 to optimally receive forward link
`signals 180 transmitted from the base station 160, and
`reduce the reception of signals from other adjacent base
`stations. Due to the controllable nature and the indepen-
`dence of the weight control components for each antenna
`element 101 through 105, only forward link signals 180
`arriving from a direction that is moreorless in the location
`of the base station 160 are optimally received. The elements
`101 through 105 naturally reject other signals that are not
`transmitted from directions proximate the intended forward
`link signals 180. In other words, a di