CA2245737A1 - Method and apparatus for polarization diversity in a base station using a plurality of reception antennas - Google Patents

Abstract

A base station (300) for communicating with at least one mobile station in a cellular communications system includes a plurality of receive antennas (322a-322e) wherein each receive antenna is oriented to define a respective receive coverage area. The antennas are supported by a support structure (318) so that a first receive antenna defines a first receive coverage area (352) and a second receive antenna defines a second receive coverage area (354) overlapping a portion of the first receive coverage area (358). First and second wideband receivers (332a, b) are operatively connected to respective first and second antennas (322a, b). The first wideband receiver receives a first plurality of receive channels from the first receive coverage area, and the second wideband receiver receives a second plurality of receive channels from the second receive coverage area. The first and second pluralities of receive channels include at least one common receive channel. The base station also includes first and second channel splitters (336a, b) operatively connected to the respective first and second wideband receivers for separating the first and second pluralities of receive channels. A diversity combiner (338b) is operatively connected to the first and second channel splitters for combining the common receive channel from the first and second channel splitters. Accordingly, an enhanced quality output receive channel is produced.

Description

CA 0 2 2 4 ~ 7 3 7 1 9 9 8 - 0 8 - 0 4 . . ~ J ~ J I~

WIDEB~ND DIGITIZATION SYSTEMS ~N~
M~TI iO~ ~OR C~LLULAR RACI~TELEPHONE~S

Field o~ Ir3venffon The pr~erit imention is rel~ted to systems and methods fcr wireless communicaticns, 2nd mc~r2 particul~rly to system~ and meth~d~ ,or wireless cellul~r c~mmunications.

Bacl~groun~ of the Inventlon Cellular cemmunic~tlans ~y~t~ms aro c~mman,y employed to pr~vida voics and ~ta c~rnmunications to ~ plura!ity of m~bile units or ~ubs~ribers. Analo~ cellul~r Qys~sms, s~ch as designated AMPS, ETACS, NI~T-1G 450, and ~MT-~00, have been de~loyed suc~essfully throu~hout the world, Mcre recPnt~y, ~isibl ~llular systsms such ~s d~signated IS~4B in North America and the pan-Furope~n GSM system have bPan introduced. These ~ystems, and other~, 3r~ describeci, for ~xample, in th~ k titled Ce)/ular Rad~o Sy~tems by Balston, ~tal., pu~lished ~yArtech Hou~e, Nor~ood, MA., 19~3.
Frequency r~u~e is ~mmonly ernployed in ~l~ular techn~logy wherein 3roups cf fr~quencie8 are allo~at~d for us~ In re~ions of limit~d geo~raphic coverag~ knawn as C~!115, CBilS containlng equi~ alent groups of ~requencies are ~e~graphic311y separated to allow mobile units in ~ifFererlt cells to simultarieously u-Qe the same fr~uency without inter~rin~ wi~h each ~ther, By 20 ~ doin~, many thcusanci3 of su~crib~rs may b~ se~ed by a ~ys~m of only several hundred frequencies.

RFPLACEilAENT PP.GE

CA 0 2 2 4 5 7 3 7 19 9 8 - 0 8 - 0 4 ~ '3 ' "J9 ~, 1 t,5

-2-~ n the lJnite~ States, for oxample, Federal allthoritie~ have allocated to cell~l~r ~cmm~lni~ati~ns a ~loc~ the UHF ~requen~y 3pectrum furtharsubdivlded Into pair~ of n~r~w frequency bandç called ~hannels. Channei pairing re~uits from the nequency dup!ex' arran~m~nt wh~rein ~he transmit and 5 recPiYe ~requencie~ in each p~ir are offset by 4~ MHz. At pres~nt the~ are ~32, 30-KI Iz wide, radio channsls allocated to cellular mcbile comrnunicatlons in the United Sta~s. To address th~ capacity iimitatians of thls ~nalog system ~ digital tr~nsmlssion ~tan~arci has been provi~ed, desi~nated IS-54B, wherein these frequ~ncy channels are further subdiYid~d into 3 time slots. 1~ th~ 1900 MHz 1~ bands, the ~CS1900 c~llular standard provi~es 200 KH~ channe!s each divid~d into aisht ~Ime slots.
As illu~;trated in Figure t, a cellular communication sys~m 20 as in the prior art includes, ~ne ~r rnors mobile stations or units 21, one or mcr~ bas~
~tatlons 23 and a mobile telephone switching office ~MTSO) 25. Although only 15 thr e cells 3B are shown in Figur& 1, a typical c~llular ne~ork may ~mprise h~zndreds of ba~e ~tations, thousa~ld~ of rnobil~ s~ations and more than vns MTS~. Each c~ll wiil have ailocated to it one or more dedicated contr~l channelsand one or more voi~ ch~nn~ls. A typical c~ll may haYe, for example, one ~ntrol channe!, aQd 21 ~oic31data. or tr~ffic, channels. ~he c~n~rol channsi is a 20 dedicated ch~nnel used for transmitting cell i~entificatlon and pagin~ infcrmation.
The trafflc cha~nels carry the Yoice and dzta in~orrnation.

~PLAC MEh~ PAG~

CA 0224~737 1998-08-04 ~ WO97/37441 PCT~S97/05105 The MTSO 25 ls the central coordinating element of the overal~ cellular network 20. It typically includes a cellular processor 28, a cellular switch 29 and also provides the interface to the public switched telephone network (PSTN) 30. Through the cellular network 20, a duplex radio communication link 32 may be effected between two mobile stations 21 or, between a mobile station 21 and a landline telephone user 33. The ~unction o~ the base station 23 is commonly to handle the radio communication with the mobile station 21. In this capacity, the base station 23 functions chiefly as a relay station for data and voice signals. The base station 23 also supervises the quality of the link 32 and monitors the received signal strength from the mobile station 21.
A typical base station 23 as in the prior art is schematically illustrated in Figure 2 which shows, as an example, the functional components of model number RBS 882 manufactured by Ericsson Telecom AB, Stockholm, Sweden for the CMS 8800 cellular mobile telephone system. A full description o~ this analog cellular network is provided in publication number EN/LZT 101 908 R2B, published by Erlcsson Telecom AB.
A now common sight along many highways, the base station 23 includes a control unit 34 and an antenna tower 35. The control unit 34 comprises the base station electronics and is usually positioned within a ruggedized enclosure at, or near, the base of the tower. Within this enclosure are the radio control group 37, or RCG, an exchange radio inter~ace (ERI) 38 and a primary power supply 41 for converting electric power from the AC grid to power the individual components within the base station 23, and a backup power supply 42.
The ERI 38 provides signals between the MTS0 25 and the base station 23. The ERI 38 receives data from the RCG 37 and transfers it to the MTSO 25 on a CA 0224~737 1998-08-04 W O 97/37441 PCTrUS97/05105 dedicated MTS0-BS link 45. In the reverse direction, the ERI 38 receives data from the MTSO 25 and sends it the RCG 37 for subsequent transmission to a mobile station 21.
The radio control group 37 includes the electronic equipment necessary to effect radio communications. A functional block diagram of an RCG
37 as in the prior art is shown in Figure 3. The con~iguration shown illustrates one control channel transmit/receive module (TRM) 51, a number of voice channel TRMs 52, and one signal strength receiver 53, as is a typical configuration required to serve one cell or sector of a cell. Each TRM 51, 52 includes a respective transmitter 54, receiver 55 and control unit 57. The TRMs 51, 52 are not typically frequency agile and operate instead on only one predetermined channel.
Control signals ~rom the ERI 38 are received by the individual control units 57. Voice and data traffic signals are routed over a separate interface to the ERI
38.
Each individual transmitter 54 for control and voice is connected to a transmit combiner 58. The transmit combiner combines all of the input signals onto a single output coupled through~a coaxial cable 62 to the transmit antenna 63. Through the use of the combiner 58, up to 16 transmitters 54 can typically be connected to a common transmit antenna 63. The combiner 58 is used because there is often a premium for space on the masts and towers used to support the antennas. In an extreme case, one mast may be required to support over 100 radio channels.
On the receive side, each o~ two receive antennas 65 is coupled to a respective receive combiner 66A, 66B where the signals received are separated according to ~requency and passed on to the individual receivers 55 in each of the TRMs 51, 52. The two receive antennas 65 are typically spaced 3 to 5 meters _ CA 0224~737 1998-08-04 WO97/37441 PCT~S97/05105 apart on the tower so that they may receive signals with uncorrelated fading patterns to thereby provide space diversity reception. There are many conventional techniques for both pre-detection and post-detection diversity which are described, ~or example, in Chapter 10 of the book entitled "Mobil e Communica~ions Engineering", by William C.Y. Lee, published by McGraw-Hill, ~992.
One visible feature of a typical base station 23 is the antenna tower 35. In order to achieve a reasonable coverage area, the antennas 63, 65 are desirably mounted at some distance above the ground.
Referring now addltionally to the prior art schematic plan view illustration of Figure 4A, in rural areas the towers 35 are commonly located at the center of a cell 36 thereby providing omni-directional coverage. In an omni-directional cell, the control channel(s) and the active voice channel(s) are broadcast in all areas of the cell -- usually ~rom a single antenna. Where base stations 23 are more densely located, a sectorized antenna system may be employed as in the prior art, and shown by the schematic diagram of Figure 4B.
Sectorization requires directional antennas 7~ having, ~or example, a 120 degree radiation pattern as illustrated in Figure 4B. Each sector 71 is itself a cell having its own control channel(s) and tra~fic channel(s). Note that "channel" may refer to a specific carrier frequency in an analog system or to a specific carrier/slot combination in a hybrid TDMA/FDMA
system, such as IS-54 and GSM.
Figure 5A illustrates a typical antenna system as in the prior art and as discussed above.
Figure 5B illustrates two types of prior art antennas that have been hereto~ore discussed -- an omni-directional antenna, such as a dipole 66, and a directional sector antenna 70 which further includes a reflector 64, ~or example. It being understood that - ~ CA 02245737 1998 - 08 - 04 " I .J_~ t;.~

transmit and rec~ive antenna~ are ty,~lcally ~f the same type f~r a givQn base ~tation.
The use of sc~nnin~ ph~g~c array ant~n~s in c~llul~
cs:rnmunic~tions systern~ has Deen pr~po~d. Fcr ~Xample, ~t~pleton, ~t al" A
~e~ JarBase Ph~sgdAr~yA~2nna System, Proc~din3s of the 93rd IEEE
VTC, pp. ~3-96 de~clibe a circular array o~ mono,~le ra~iating elements t~
pro~Ade 3~0 dPgr~e sc~nning c~pability. Stapleton's antenna is desiQnatec~ such that eac~ radi~ting el~mer.t has the poten7i~1 of tr~nsrnittlng on every channelalloc~ted to the cell.
It should be noted th~t pa~ive micrc~trlp arrays ar~ curr~ntly avali~ble for use with c~llular bas~ s~aticn~. F~r ~arnple, type no. 1309.41.00C9 manufact~red by H~b~r~Suhner AG of Hericau, 3witzerand i~ a ~even element linearly pola~ized flat panel pa~ive antenna with a shaped elevati~n ~eam for use in c~lluiar b~se stations. l~his arr~y ~an r~pla~ ths typical dip~le antenna1~ and is mor~ suitable fcr locat,sns on the sides of buildin~s or Gther Rat surfaca~.
In appiicaticn note 20.3, published by Huber~Suhner, it is shown that wide are~
covera~e may be obtained via the us~ of pGwer~splitters whereby pcrtions of the signals are di~/erted tG sev~r~l indi~id~al panel~.
A sectorized c~llular radIo base statlon antenna is discu~sed in Eur~pe~n Publication hlo. ~ 5~1 770 A2 to Dumbnll et al. and published Apnl 13, 1994. A~ discussed, a ~ctori~ed cel!ul~r radio b~s2 stati~n compris~s a plurality cf an~ul~rly sep~rated direc~onal transmit antennas, ~ p3urality of angularly separated directional re~iYe antPnnas, and diversi~ mbinin~ means ~r combining ~i~nals from adjac~nt r~c~ive ant~nn2s.
l'he per~rm~nce of diver~ity r~ception inc. e~ses a~ the number of diversi~y antennas i8 increased. However, there may not be spaGe on the ~nt~nna tcwer to provide a plur~lity o~ diversity ant~nnas for each 120~ or ~0~
~ctor. Mor~oover, th~ need for a co~ ,pondlng plurality o~ divergity r~elving s~annels ~or each r~io ~ nnel rnay Increase ~sts. In ad~it,on, the ori~ntatlon of the lineariy polsrlzed m~bil~ ant~nna may not 21way~ be in ~lignment wlth thetypic~lly verticail~J polarized reoeive antenn~ at the ba~e station. Furthermore, recAptlon at ~he moblle station ~ay also be subje~t to fadin~.

REPLACEM~I~iT PAG~

CA 0224~737 1998-08-04 - WO 97/37441 PCT~US97/05105 Summarv o~ the Invention In view of the ~oregoing background, it is therefore an ob~ect of the present invention to provide an economic cellular communications system base station capable of providing enhanced communication with a mobile station, particularly in view of fading and/or misorientation of the antenna.
This and other objects, advantages and features of the present invention are provided by a base station comprising a plurality of antennas including a first receive antenna defining a first receive coverage area and a second receive antenna defining a second receive coverage area overlapping a portion of the first receive coverage area. Respective wideband receivers are connected to each o~ the ~irs~
and second antennas, and each wideband receiver receives a plurality of receive channels from the respective receive coverage area. Furthermore, a~
least one channel from each plurality of receive channels received by the wideband receivers is a common receive channel.
Accordingly, a mobile station transmitting from the overlap coverage area on the common receive channel is received by both the firs~ and second wideband receivers thereby providing for diversity combination. In addition, the wideband receivers provide that a plurality of channels operating on a plurality of frequencies are received by each antenna without requiring a plurality of receivers.
The base station also includes first and second channel splitters operatively connected to the respective wideband receivers for separating the first and second pluralities of receive channels. In particular, the common receive channel is separated from each plurality o~ receive channels. A diversity combiner is operatively connected to each of the ch~nn~l splitters and combines the common receive CA 0224~737 1998-08-04 ~ W O 97/37441 PCT~US97105105 channel from the first and second channel splitters in order to produce an enhanced quality output receive channel.
The first antenna may receive signals having a ~irst polarization and the second antenna may receive signals having a second polarization allowing the diversity combiner to combine the common receive channel by polarization diversity combination.
Furthermore, the first polarization may be right-hand-circular polarization and the second polarization maybe le~t-hand-circular polarization. Accordingly, each antenna may be implemented as an array of patch antenna elements on an elongate substrate.
Furthermore, the different polarizations allow each antenna to both receive and transmit by using polarization isolation. For example the ~irst antenna may define a ~irst transmit coverage area and transmit signals having the second polarization, and the second antenna may de~ine a second transmit coverage area and transmit signals having the first polarization. In addition, the first and second antennas may be adjacent antennas. Accordingly, the base station can include a plurality of circularly arranged antennas wherein every other antenna receives signals having the same polarization and adjacent antennas have overlapping receive coverage areas. This arrangement allows the base station to receive signals from any direction while providing diversity combination.
Each of the receive channels may operate on a predetermined ~requency, and the first and second pluralities of receive channels may each comprise receive channels operating on consecutive predetermined ~re~uencies. Accordingly, the bandwidth o~ the first and second wideband receivers may be reduced thereby reducing the cost o~ the base station.

CA 0224~737 1998-08-04 W O 97/37441 PCTrUS97/OSlOS
_g _ Higher order diversity combination can be accommodated by providing more antennas on the base station which define receive coverage areas overlapping the overlap receive coverage area. For example, a third receive antenna may define a third receive coverage area overlapping portions o~ the first and second receive coverage areas. In addition, a third wideband receiver operatively connected to the third antenna may be adapted to receive a third plurality o~
receive channels ~rom the third receive coverage area and the third plurality of receive channels may include the at least one common receive channel. A third channel splitter may separate the third plurality of receive channels and the diversity combiner may combine the common receive channel from the ~irst, second, and third channel splitters.
The base station of the present invention provides diversity combination of a receive channel which is received by two or more antennas on the base station. Accordingly, an enhanced ~uality output channel is produced. In addition, by using a wideband receiver with each antenna, a plurality of receive channels operating on a plurality of frequencies can be received at each antenna without requiring a separate receiver ~or each ~reque~cy for each antenna.
In addition, the bandwidth of each wideband receiver can be reduced by providing that individual wideband receivers receive consecutive ~requencies. By reducing the bandwidth required for the ma~ority o~ the wideband receivers, the overall cost of the system can be reduced.

Brief Description of the Drawings Figure 1 is a schematic block diagram illustrating the basic components of a cellular communications system as in the prior art.

CA 0224~737 1998-08-04 W O 97/37441 PCT~US97/05105 Figure 2 is a schematic block diagram illustrating the functional component~ of ~ cellular communications base station as in the prior art.
Figure 3 is a schematic block diagram illustrating the functional elements of Radio Control Group of a base station as in the prior art.
Figure 4A is a schematic plan view illustrating an omni-directional cellular pattern as in the prior art.
Figure 4B is a schematic plan view illustrating a sectorized cellular pattern as in the prior art.
Figure 5A is a schematic side view illustrating a typical cellular antenna system as in the prior art.
Figure 5B is a schematic side view illustrating an omni-directional antenna and a sector antenna as in the prior art.
Figure 6 is a plan view of~a base station including a plurality of antennas according to the present invention.
Figure 7 is a top view of the base station of Figure 6.
Figure 8 is a cut away view of an antenna including a plurality of patch antenna elements on an elongate substrate according to Figure 6.
Figure 9 is a schematic view of an antenna according to Figure 8.
Figure 10 is a front perspective view of a single patch antenna element on an elongate substrate according to Figure 8.
Figure 11 is a rear perspective view of a single patch antenna element on an elongate substrate according to Figure 8.
Figures 12A-C are block diagrams of the antennas of Figure 6 together with the associated processing blocks.

CA 02245737 l998-08-04 W O 97/37441 PCT~US97/OSlOS

Figure 13 is a top view of a portion o~ the base station of Figure 6 illustrating thr~e adjacent antennas and the respective overlapping receive coverage areas.

Detailed DescriPtion The present invention now will be described more ~ully hereina~ter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the ~cope of the invention to one having skill in the art. Like numbers re~er to like elements throughout.
Refer~ing first to Figures 6 and 7, a base station 300 including a plurality of antennas 322a-1 is described. The antennas are arranged in a cylindrical pattern to receive signals ~rom any direction. In addition, alternating antennas may be arranged to receive signals having alternating polarizations. For example, antennas 322a, 322c, 322e, 322g, 322i, and 322k can receive signals having a ~irst rotational polarization, while antennas 322b, 322d, 322~, 322h, 322j, and 3221 receive signals having a second rotational polarization. More particularly, antennas 322a, 322c, 322e, 322g, 322i, and 322k can receive signals having right-hand-circular polarization, and antennas 322b, 322d, 322~, 322h, 322j, and 3221 can receive signals having left-hand-circular polarization In addition, each of these antennas can transmit using a polarization opposite that used to receive.
Alternately, each antenna can receive both polarizations.

, CA 0224~737 1998-08-04 W O 97/37441 PCTrUS97/0510 Each of the antennas 322a-l preferably includes a plurality of recei~e antenna elements for receiving signals having a predetermined rotational polarization as discussed above. These antenna elements are arranged in a predetermined pattern to define respective receive coverage areas for each of these antennas. The antenna elements may be circular patch antenna elements (as illustrated in Figures 8 and 9) or crossed dipoles as would be readily understood by one having skill in the art. In addition, these antenna elements may serve simultaneously as transmit antenna elements. Antenna mounting means, such as the illustrated antenna mast 318, is preferably provided for mounting the antennas so that the adjacent receive coverage areas de~ined by adjacent antennas are overlapping.
A cut away of a single antenna 322 is illustrated in Figure 8. In a pre~erred embodiment, the antenna includes a plurality of printed circuit board antenna elements 224, such as patch antenna elements. The patch antenna elements 224 are provided on an elongate substrate 226 such as a printed circuit board, and these patch antenna elements can be used as transmit and receive elements simultaneously. The elongate substrate may also be provided with other components such as transmit power amplifiers 228, input 230b or transmit 230a ~ilters, a common receive low noise amplifier ("LNA") 231, and an output filter 232b or receive filter 232a, as illustrated schematically in Figure 9. As further illustrated in Figure 8, the elongate substrate 226, with patch antennas 224 is preferably enclosed in a radio-transparent, weatherproo~ tubular housing 234. A mounting bracket 236 can be used to connect the antenna to the ~ase station mast, and the cable 220 can be used to connect the antenna 322 to the wideband recei~ers (illustrated in Figure 12). In addition, a temperature sensor and CA 0224~737 1998-08-04 W O 97/37441 PCTrUS97/05105 heater can be lncluded within the housing for colder climates.
As shown schematically in Figure 9, each antenna element 224 is coupled by first coupling circuit 238 including first coupling line 239 to a common receive filter 232a and low-noise receive amplifier 231. A second coupling circuit 240 including coupling line 241 distributes a tran8mit signal to the transmit power amplifiers 228. As would be readily understood by one having skill in the art, the transmit ampli~iers may be either single carrier power amplifiers (SCPA' 9) for amplifying a Time Division Multiple Access (TDMA) signal, or multi-carrier power amplifier's (MCPA's) for amplifying a composite of several different carrier frequency signals. In the case that SCPA's are used, a signal is directed towards a single principle direction on a single frequency, while if MCPA's are used, multiple signals on different frequencies can be directed in each direction. In the receive direction, however, the receive low noise amplifier 231 is pre~erably always capable of receiving and amplifying signals on multiple frequencies. In addition to coupling line 240, the second coupling circuit may include switching means for dynamically partitioning the transmit array to provide transmit sub-arrays operating on different ~requencies in the same time slot.
The transmit amplifiers 228 may produce wideband noise outputs at frequencies overlapping the receive i~requency band and be of sufficient level to degrade the noise figure of the receive low noise amplifier 231. Accordingly, a transmit filter 230a and receive filter 232a can be used as illustrated. The receive filter 232a may be a band-pass filter tuned to pass the receive ~requency band ~n~ attenuate transmit frequency signals, while the transmit filter 230a or input filter 230b can be notch filters to attenuate CA 0224~737 1998-08-04 W O 97/37441 P~TrUS97/0510S

transmission in the receive frequency band and pass the transmit frequency band.
As would be readily understood by one having skill in the art, directivity f~voring reception is one way to improve received signal quality. Another way to improve the received signal quality is diversity reception using two or more preferably independent channels, for example, on widely spaced antennas (space diversity), different fre~uencies (frequency diversity) or different polarizations. The use of different polarizations gives independent fading even when the antennas cannot be widely spaced. Considerable diversity gain is available when combining signals from sources suf~ering from uncorrelated fading in a joint signal processor, as distinct from just combining signals from different antenna array elements to obtain directive gain. --Typically combining signals from twodifferent antennas experiencing the same signal fading will yield a gain of approximately 3dB while if the fading is uncorrelated Rayleigh, gains on the order of 7dB may be obtained. Fading can be uncorrelated on two antennas spaced only inches apart on a mobile phone, but unfortunately, due to a geometric magnification effect, the spacing required at a base station can be hundreds of times greater. Relatively close spacing is possible at the mobile station because the multiple paths that cause fading tend to arise due to near field clutter in the vicinity of the mobile station, such as due to reflections from objects within a few tens or hundreds o~ yards. In the reverse direction, however, these reflections may propagate several miles to the base station causing the geometric magnification of the antenna spacing required at the base station.
Accordingly, a spacing of several feet between adjacent antennas at the base station may be insu~ficient to obtain uncorrelated fading through space diversity.

CA 0224~737 1998-08-04 ~ WO97137441 PCT~S97/05105 On the other hand, it is observed that fading is largely uncorrelated when comparing antennas o~
orthogonal polarizations. Accordingly, the alternate antennas are preferably orthogonally polarized. For example, each of antennas 322a, 322c, 322e, 322g, 322i, and 322k, may use orthogonal rotational polarizations such as right-hand-circular-polarization (RHCP) for receiving and left-hand-circular-polarization (LHCP) for transmitting, while each of antennas 322b, 322d, 322f, 322h, 322j, and 3221 may use the opposite polarizations for receiving and transmitting.
Accordingly, polarization isolation can be used in a preferred embodiment to help isolate the transmit and receive signals. The receive paths preferably have multi-carrier capability even if the transmitting paths have only single-carrier capability. Therefore, the received signals are received with both RHCP and LHCP
which exhibit uncorrelated fading. Upon processing the signals from two or more antennas, a diversity gain is obtained which is greater than the directive gain that would have been obtained had all antennas had like receive polarization.
As will be understood by one having skill in the art with reference to Figure 8, each antenna is preferably fabricated separately on an elongate substrate 226 such as a long thin module or printed circuit board. Printed circuit board antenna elements, such as patch antennas, may be readily fabricated as part of such a module as would be readily understood by one having skill in the art. As shown in Figures 10 and 11, a circular patch antenna element 224 may be fed at two feed points 270 and 272, and the two feed points connected to a printed, branch-line quadrature coupler 274 to provide two feed points 270 and 272 of opposite circular or rotational polarization. A ground connection 276 can be used to connect the antenna element 224 to a ground plane 278 shown sandwiched CA 0224~737 1998-08-04 W O 97/37441 PCT~US97/05105 between two layers of the elongate substrate 226. As will be understood by one having skill in the art, active elements, such as amplifiers, and passive elements, such as filters, may also be mounted or constructed on the elongate substrate.
Multiple antennas may be mounted on a single antenna mount. Each antenna thereby provides directivity in the azimuthal plane as well as a narrow beam in the vertical plane, and the antennas may be oriented to cover different azimuthal sectors. This can be done by mounting different collinear antennas around the antenna mast at the same height but pointing to dif~erent azimuthal sectors, or by mounting two or more antennas above each other polnting to the same or different azimuthal sectors. In fact, the azimuthal pointing of an antenna may be set independently of where it is mounted, but it is preferred that the antennas be directed so that there is no interference from the other antennas or the mast.
The base station 300 preferably includes a plurality of antennas 322a-l arranged in a circular pattern, as shown in Figures 6 and 7. Signals received from each antenna are applied to respective wideband receivers 332a-l as shown in Figures 12A-C. Signal loss between the antennas and wideband receivers can be reduced by integrating masthead preamplifiers into the antenna assembly of Figure 8. The masthead preamplifiers provide ~ains ahead of cables used to connect the antennas and wideband receivers.
Optionally, masthead down conversion to an intermediate frequency can be used.
As will be understood by one having skill in the art, a wideband receiver is a receiver which receives signals having frequencies over a predetermined range of frequencies so that a plurality of cellular ~requencies is received. As discussed in U.S. Patent Application Serial No. 08/601,768, entitled CA 0224~737 1998-08-04 ~WO97/37441 PCT~S97/0510 I'Multichannel Receiver Using Analysis By Synthesis" to Paul W. Dent, and filed February 15, 1996, a wideband receiver can separate individual frequency channels ~ spaced, for example, by 30 KHz (AMPS~ or 200 KHz (PCSl900). This application is hereby incorporated herein in its entirety by reference.
The use of wideband receivers al~ows a plurality of frequencies to be received at each antenna without requiring a plurality of single frequency receivers to be connected to each antenna. In the embodiment shown in Figure 8, the base station is adapted to receive twelve frequencies, and each wideband receiver is adapted to receive three of these frequencies. In particular, each ~requency is received by three adjacent antennas and associated wideband receivers.
As an example, the wideband receivers can be adapted so that each antenna 322a-l receives three frequencies f as shown in Table l.

Table l Antenna Frequencies 322a f12, f1, f2 322b f1, f2, f3 322c f2, f3 f4 322d f3, f4, fs 322e f4, fs~ f6 322f f5, f6, f7 322g f6, f7, f8 322h f7, f8, fg 322i f8, fg, f1o 322j fg~ f10, 322k f10, f11, f12 3221 f11, f12, f1 Each frequency for the base station is received by three adjacent antennas and respective wideband receivers, and as previously discussed, alternating antennas receive the frequency with alternating polarizations. Accordingly, polarization diversity reception can be achieved.

CA 0224~737 1998-08-04 W O 97/37441 ~CT~US97/05105 Each receive channel operatee on a predetermined ~requency which is allocated to the base station. As shown in Table 1, a base station with 12 antennas can be allocated 12 frequencies fl-l2, and each wideband receiver can be=adapted to receive a unique combination of three o~ these frequencies.
Furthermore, each frequency is preferably received by three adjacent antennas defining an overlap receive coverage area common to all three antennas.
By allocating the frequencies as shown in Table 1, and providing that:

f~ c2~f3<f4cf5cf6<f7cf8cf9cfi(~cfllcfl2 or alternately that:
fl>f2>f3>f;~>fS>f6>f7>f8>f9>flD>fll>fl2 the bandwidth of the wideband receivers can be reduced.
In particular, wideband receivers 332b-k can be adapted to receive consecutive frequencies. Only wideband receivers 332a and 3321 receive non-consecutive ~requencies in this arrangement. By reducing the bandwidth required ~or the majority o~ the wideband receivers, the overall cost o~ the system can be reduced. Furthermore, the circle o~ overlapping receivers can be extended to greater than one full turn of 360~ by adding receivers for frequencies ~13-~24 using the same antennas. Only the first and last receivers in this sequence do not receive consecutive channels.
As will be understood by one having skill in the art, each frequency can support one or more cellular communication receive channels. For example, in a cellular system supporting a Time Division Multiple Access ("TDMA") standard such as GSM, each frequency can be divided into eight receive channels.
Accordingly, each channel is received by three antennas in the example of Table 1. Furthermore, higher orders of diversity can be achieved by providin~antennas and CA 0224~737 1998-08-04 W O 97/37441 PCTrUS97105105 wideband receivers capable of receiving more ~requencies, thus obtaining overlap of frequency for more than three ante~nas. For example, each frequency ~and therefor each receive channel~ can be received by five adjacent antennas using 5-channel wideband receivers.
As shown in Figures 12A-C, a wideband receiver 332a is operatively connected ~o each respective antenna 322a. The wideband receiver ~or each antenna is adapted to receive a predetermined plurality of receive channels ~rom a receive coverage area (shown in Figure 13) for that antenna. For example, each wideband receiver can receive three frequencies with as many as eight time slots per frequency, when TDMA is used. ~ideband A-to-D
converters 334a-1 can be used to convert the signal generated by the respective wideband receiver 332a-1 into a digital signal. These digital signals can then be separated into separate receive channels by respective digital channel splitters 336a according to frequency and time slot. Respective diversity combiners 338a-1 combine common receive channels from adjacent antennas to produce an enhanced quality output receive channel.
In the embodiment of Figures 12A-C, three frequencies are received by each antenna, and each frequency supports one receive channel using FDMA or multiple channels using TDMA having mul~iple time slots. It will be understood by one having skill in the art that the diversity combiners can operate sequentially for each time slot in order to adapt to different mobile signals in each time slot arriving ~rom slightly different directions within the same sector. Furthermore, a single frequency can be received by more than three antennas by providing the appropriate wideband receivers, and making the CA 0224~737 1998-08-04 W O 97/37441 PCTrUS97/05105 additional eonneetions between the ehannel splitters and the diversity eombiners.
In Figure 13, three adjaeent antennas 322a-e from the base station 300 of Figures 7 and 8 are illustrated together with the assoeiated wideband reeeivers 332a-e, wideband analog-to-digital converters 334a-e, ehannel splitters 336a-e, and diversity combiner used to process a reeeive ehannel from a mobile ~tation 350, such as an automobile cellular radiotelephone. As shown, a support structure such as an antenna mast 318 is used to support the antennas so that eaeh antenna defines a respective receive eoverage area, and a portion of all three receive coverage areas overlap. The first antenna 322a defines the flrst reeeive eoverage area 352, the seeond antenna 322b defines the seeond receive coverage area 254, and the third antenna 322e defines the third receive coverage area 356. Portions of all three receive coverage areas overlap in the overlap eoverage area 358.
In addition, the wideband receivers 332a-e are each adapted to reeeive a common recelve ~requeney, and this common receive ~requency ean aeeommodate one or more common receive channels using TDMA time slots or CDMA eodes. For purposes of deseription, a single eommon receive ehannel will be described, but one having skill in the art will understand that multiple channels can be accommodated according to the present invention using TDMA or CDMA on a single frequency ehannel. Aceordingly, ~he mobile station 350 in the overlap eoverage area 358 ean transmit over the common receive channel on the common fre~uency to all three antennas 322a simultaneously.
The ehannel is reeeived at each of the wideband receivers 332a-e and converted to digital signals by each of the wideband analog-to-digital eonverters 334a-e. In addition, other ehannels on other frequeneies can be reeeived by eaeh of the CA 0224~737 1998-08-04 ~ W O97137441 PCTrUS97/05105 antennas and wideband receivers. Accordingly, the digital splitters separate the common receive channel.
Because each of the three antennas receive the common receive channel ~rom a different path, the diversity combiner 338b is used to combine the common receive channel as received by each of the antennas in order to produce an enhanced quality receive channel. As will be understood by one having skill in the art, the wideband analog-to-digital converters, channel splitters, and diversit~ combiners can be implemented separately or in combination using special purpose computers, general purpose computers with special purpose software, special purpose hardware, or combinations thereof.
In particular, the ~irst antenna 332a and third antenna 332c can receive signals having a first polarization, and the second antenna 332b can receive signals having a second polarization different ~rom the first polarization. Accordingly, the signals can be combined using a polarization diversity combiner. More particularly, the first polarization can be right-hand-circular polarization, and the second polarization can be le~t-hand-circular polarization.
By using antennas comprising arrays of patch antenna elements 224 as illustrated in Figures 8, 9, 10, and 11, the antennas can transmit as well as receive. By transmitting on a polarization opposite that used to receive, polarization isolation can be used to accommodate both transmission and reception.
For example, the ~irst antenna 322a and third antenna 322c de~ine first and third transmit coverage areas which can be the same as the respective receive coverage areas, and the second antenna 322b defines a second transmit coverage area that can be the same as the second receive coverage area. The first and third antennas receive signals having a ~irst polarization such as right-hand-circular polarization, and transmit ' ~ t l 7 ~ t /-7 ' ,; ~ ~

- CA 0 2 2 4 5 7 3 7 19 9 8 - 0 8 - 0 4 1 . ~ 1 i 1 J ~ ,3~ ;"

si~nals havir~ a sewnd p~la~zation 3uch ~s la~hand~irGul~r polari~ation. Th.
s~cond antenna r~eiv~s signals h~vin~ ~h~ secc~nd polarizat~on and transmits sisnals having th~ flr8t polar~zation. ~hen a m~bil~ reG~iYer lies in ~hQ ovar~ap r~gion ~ehv~en two antenna p~tt~rns, ~item~ts I CMA burs~ destined for that mo~le recPiver may b~ tran~mitted frcm first a~rn~tin~ with ~ sec~nd ~ntenna of opposite polari2ation, thus ob~ining polariz~tian diversity transmission~
While th~ comn~cn receiv~ ~hanr~e~ is shcwn as being rec~lved by three anter1nas on the ~e station~ one havins skill In the ~rt will un~rst~n~ tha the channel can be re~ive~ by mcre ant~nna~ slm~ n40us!y. For examFle, in 1~ a base ~tion with 12 ant~nnas ~venly spa~ed in a c~r~ular patt~rn ar~und a rnast w~h each ant~nna de~inir;~ a 12~C a,imut~al r~ceive covera~s area, up to Q~v~n antenn~is can rec~ive 3 channel being tr~nsmlnsd by 3 ~ingle m~bile staticr~. In this case, ea~h wid~band re~iver can r~GPive seven firequencizs ande~ch diversity c~mbiner can b~ conneet~d to saven channei splitters t~ c~mbine 1~- channels ~rom ~h~ s~en antenn~s.
The diver~ity ccrribin~rs 338a~1 preferably inciud~ .~ignal quality determining means fol determining ~ignai-to-n~ise r~tio-e cf the r~spective ~c~ive channel~, and wei~hting mean3 ~r weighting the ~ec~ive channel~ based upon the respectiYe ~l~nal-to~noi~e r~tios theraaf to ther~y generate the enhanc~d ZO qu21ity output receive signal. ~n~ det~rminaticn of sisnal-te-noise ratios and wei~h~e~ pr~c~s~lng of diverse rec~i~/e ~i~nals is~disclosed in U.S. P tent No.
5,131,~8 to ~ckstr~rn 6t ai., the ~ntire disc!cg~Jre of which is inc~rpora~d hersin by referenc~. In addition, IJ,S, P~it~nt hio. 5~4~,272 (patent appli~iticn serial no. Q8J2~1 ,Z023 entitied I~Diversi~y Rec&iYe~ for Si~n~ls With ~1ultipath Tirne Dlspersi~n" to Bot~omley an~i filed M~y ~1, 1 994 disc~oses an ~It~rnate di~rsity re~eiver t~chnique. Th~ di~c!o~u~e or thi~ pat~nt i8 her~by incorpo~ated herPIn by re~rence.
Aitemately, both pol~ ations can be receive~ on each antenna, ~ither by c~ tn~ r2c~ive only antsnnas or by using duplexing filt~rs in pla~e of transmit filters 230a, as shown in Figur~ ~. In this cas~, a fi~t r~c~ive cignal havin~ a poia~ on orth~g~nal wi~h respe~ to th~ transmit si~nal is fed to the amplifier 231, as ~efor~. In ad~iti~n, a second re~lved ~ignal i8 separa~d from the transmit p~th, wher~in the se~nd rec~lved sisnal has ths sam~ p~ari~ation as the tr~nQmitt~d sign~l. A separ2te ampliller, similar to ~rnplifier ~31 can be ~EPL4~EM Nl~ PAGE

, , . ,; ~",, ,.. , ........ J ~ . jrj. Il> ~ ~)LII~ +~ Y9~1~i.,.. ~ 9 CA 02245737 1998-08-04 .~

added for this extra r~csive p~th, and both pol~rlz~tion~ of rec~ived si~nal~ from one ~r m~re antennas can be f~d to resp~ctive wideband r~ceiverg.
Ea~h ~tive antenna 3~2 can in&lude 3 plurality of RF power tran~mit arnpliflers 228 ~ch coupled throu~h ~ ~rancmit fil~er 2~a to an indivi~ual radiating tr~nsmit antenna element 2iZ~! ~35 ~hown In Figure ~. The antenna el~ments 2~4 c~n be use~ to both ~ransmit and rec~i~e simul~neously.
Power can ~e distri~utPd ~o sach pawer amplifier 228 vi~ a ~awer dividin~
netwof~ such as c~uplin~ circ~it ~40. In this ~m~odiment, the abov~menticned c~mponents are prefera~ly fabricated usin~ strip1ine or micro~tnp techniqueg on a 10 mounting su~strate. such as a glass-epoxy print~d circuit 5Oard. ~s woul~ be r eadily understood ~y one h~ving skiil In the art. Dividing mean~, su~h as c~upl~ng circ~it 240, can in~lu~e ~ piuralit~ ~f inputs and switching rneans to select which input ~ignals are di~trikuted to which amplifi~r~ 228. The switching meang can b~ activ3ted by pre prc~lammed c~ntrol means to det~rmin~ for each 15 t~me slot if the full array is u~ed at one transmit fre~uellcy or if l~~PLACEMFNT PA~:;E

CA 0224~737 1998-08-04 W O 97/37441 PCTrUS97/05105 transmit sub-arrays are formed for transmitting multiple fre~uencies simultaneously.
The receive antenna elements 214 are coupled to a common output via a combining network such as coupling circuit 238. Basically the inverse of the power dividing network, the combining ~etwork coherently couples the signals received from array elements 214 into a common output. The combining network may introduce phase offsets or tapered coupling in order to effect beam shapin~ or to reduce vertical sidelobes, and to reduce unwanted deep nulls to mobiles very close to the mast.
The output of the combining network is illustratively coupled to a receive filter 232a and a low-nolse amplifier (LNA) 231. Traditionally, a similar LNA was located in the RCG of a conventional base station, and, accordingly, the received signal suffered 2-4 dB o~ transmission loss through the IFL
cabling. By locating the LNA 231 on the receive antenna 322 in accordance with another advantage o~ the present invention, losses prior to amplification are reduced thereby benefitting the overall system noise figure and allowing an increase in site/cell radius or a reduction in mobile power output to increase battery life.
The amplified receive signal from the LNA 231 is also preferably filtered to remove unwanted signal components, such as those generated by the power transmit amplifiers 228 that are not always removed by receive filter 232a. Therefore the output of LN~ 231 is preferably coupled to a band-pass filter such as output filter 232b. The band-pass filter may be a microstrip edge coupled filter, such as described in Chapter 6 of Bahl, et al., Microwave Solid State Circuit De~ign, Wiley & So~s, 1988, a high-k ceramic resonator filter, or a SAW filter. Depending on the system bandwidth and transmit/receive duplex spacing, a . .:
.

CA 0224~737 1998-08-04 WO97/37441 rCT~S97/05105 low-pass, or high-pass filter may also be acceptable as would be readily understood by one having skill in the art.
Both the transmit signals and the receive signals are coupled to/from the antennas 322a-l via a cable such as an interfacility link (IFL). The IFL
preferably comprises a bundle of coaxial cables, and power cables to provide power to the power transmit amplifiers 228 and the LNA 231.
The invention also includes a method for operating a cellular base station which communicates with at least one mobile station as shown in Figure 13.
A first receive coverage area 352 is defined by the first an~enna 322a, and a second receive coverage area 354 is de~ined by ~he second antenna 322b. These receive coverage areas overlap as shown in the overlap receive coverage area 358. A first plurality of receive channels are received from the first receive coverage area 352 by a fir~t wideband receiver 332a, and a second plurality of recelve channels are received from the second receive coverage area 354 by a second wideband receiver 332b.
The first and second pluralities of receive channels include at least one common receive channel.
The common receive channel is separated from each of the first and second pluralities of receive channels by channel splitters 336a and 336b. The common receive channel from the first receive coverage area 352 and the second receive coverage area 354 are combined by the diversity combiner 338b in order to produce an enhanced quality output receive channel.
The first plurality of receive channels can be received having a first polarization such as right-hand circular polarization, and the second plurality of receive channels can be received having a second polarization such as left-hand-circular polarization.
The method can also include the steps of transmitting CA 0224~737 1998-08-04 W~97137441 PCT~S97105105 signals having the second polarization from the first antenna 322a into the first receive coverage area 352, and transmitting signals having the first polarization from the second antenna 322b into the second receive coverage area 354. Accordingly, the same antennas can be used to both transmit and receive by using polarization isolation to separate the transmit and recelve s lgnal s .
In this method, each of the receive channels can operate on a predetermined frequency, and the first and second pluralities of receive channels can each comprise receive channels operating on consecutive predetermined frequencies. Accordingly, the bandwidth required for the wideband receivers can be reduced.
A third receive coverage area 356 can be defined by the third antenna 322e so that a portion of the third receive coverage area 356 overlaps the first and second receive coverage areas in the overlap receive coverage area 358. A third plurality of receive channels can be received from the third receive coverage area 356 by a third wideband receiver 332e, and the third plurality of receive channels preferably includes the common receive channel. The third plurality of receive channels can be separated by the channel separator 336e. Accordingly, the common receive channel from the first, second, and third channel splitters can be combined by the diversity combiner 338b.
Antenna azimuthal radiation.patterns similar to conventional 120~ sector patterns can be used such that considerable overlaps of adjacent coverage areas o~ adjacent antennas.is deliberately arranged. The space and polarization diversity combining can alternately be viewed as adaptive array processing, and can be designed either to increase desired signal reception, reduce interference, or to increase signal-to-interference ratios as described in U.S.

' L . t ~ I L . .~ ~ J ~ CA 0 2 2 4 ~ 7 3 7 1 9 9 8 - 0 8 - 0 4 -~7-Patent ~o. ~,~80,413 (Applic~t~on Serial No. 08~2~4,77~ entitle~ thod Of ArdApparatus F~r Int~rFersnr~e Rejection Gornbining In ~îu~ti-Antenna :)igital C~llular Communic~tions Systems" to ~ottoml~y. The disç~oslJrP Of this patent is hereby inc~rporatsd i~er~in ~y r~rerenc~. In ad~iti~n, ba~ ~t~tions ~nd r~ ed methods are di~cus~d in U.S. Patent No. 5,~48,813 (~ppiication Serial No. ~8~17~3C1~to Charas et ~I. entitle~ "Pha~ed Array Cellular B~e Station And As~ociat~
~lethods F~r Enhanc~ Po~er Ef'iciency'l, and in U.S~ P~tent No. 5,724,866 (Application Serial iYo. 08f43~ o ~3ent entitled "Polarization Diversiiy Phased Array C~ilular 8~s~ St~tion And Asscciateà Metho~s". Th~ disclosures 10 of both of th~se paten~ ~re h~reby inGorpol ated herein in their entir~ty by ~ r~fr~renc2.
As showr in ~igures 6 ~nd 7, the ~ase 3tation 3~0 ~f the present invention can ~e implern~nted with twelve antenna~ 322~-1 dl~tri~ut~d around the m~st 318 in ~imuth. E~ch ant~nna s~n have an azimuthal p~ rn with ~
~ignal ~Kenuation of -3~ oYer a ~05C bearnwidth and a 3i~nal ~ttenu~tion a' -12dB over a 1~234 be~mwi~th. Each antenna is pre~erably u~ed to tran~m}t or,ly asin~le frequency at a tirne. ~y uni~rrnly di~tributing the ~requencies in azim~Jth, gain arises in both ~ransmission and reception ~y conne~ting a call frcm a mcbiie st~ti~n to the antenna d2fi~ing the rec~ive co~erage area in whicn thQ m~ile ~0 station i~ most centrally lo~ated.
With twPlve antennas to choose firo T~, the m~bile sta~ion can be best ~er~ed l~y the nearest base station~ in c~ntrast to prior systems in which the neare~t base ~tation rn~y not haYe an ~ntenna pointing in the optirnum dire~tion.
With azimuthzlly di~trii~uted freq~encies, the maximum range to the ~est base stat!on with tNelYe ~ntennas can ~e re~uced ~y 4.~dB in path Icss term~. The average gain on the CJI (co-channel interference) pro~ability distribution can exp~ted to be ai~out 3d5 with 1~ antennas and about 2d~ with ~ ~ntenna~.
Fu~ther gain~ are possible through use of hi~her ~rd~r diversi~y on interferenc~reje~ion cGmbini~g.
Many modirications and other embodiments of th~ invention wi~
o~me to th~o mind of on~ skilled in the art ha~ing the benefit of the teachin~s presented in the ~regoin~ dPscriptions and th~ associat~d drawings. Therefore, it i~ to be linderstood ~h~t the invention is not to be lirnitecl to th~ ~peeific embcdliments discio~d, and t~2t modlhcations of th~se REPLAC~M~NT P~ ;iE

- W O 97/37441 PCTrUS97/05105 embodiments are intended to be included within the scope o~ the appended claims.

_

Claims (21)

THAT WHICH IS CLAIMED IS:

1. A base station (300) for communicating with at least one mobile station (350 in a cellular communications system, said base station (300)comprising a plurality of receiving antennas (322) wherein each receive antenna (322) is oriented to define a respective receive coverage area (352,354,356), and a support structure (318) for supporting said plurality of receive antennas (322) so that a first receive antenna (322a) defines a first receive coverage area (352) and a second receive antenna (322b) defines a second receive coverage area (354) overlapping a portion of said first receive coverage area, said base station characterized by:
a first wideband receiver (332a) operatively connected to said first receive antenna (322a), wherein said first wideband receiver (332a) is adapted to receive a first plurality of receive channels from said first receivecoverage area;
a second wideband receiver (332b) operatively connected to said second receive antenna (322b), wherein said second wideband receiver (332b) is adapted to receive a second plurality of receive channels from said second receive coverage area (354) and wherein said first and second pluralitiesof receive channels include at least one common receive channel;
first and second channel splitters (336a,336b) operatively connected to said respective first and second wideband receivers (332a, 332b) for separating said first and second pluralities of receive channels; and a diversity combiner (338b) operatively connected to said first and second channel splitters (336a,336b) for combining said common receive channel from said first and second channel splitters to produce an enhanced quality output receive channel.

2. A base station (300) according to Claim 1 wherein said first receive antenna (322a) receives signals having a first polarization and said second receive antenna (322b) receives signals having a second polarization different from said first polarization, and wherein said diversity combiner (338b) comprises a polarization diversity combiner.

3. A base station (300) according to Claim 2 wherein said first polarization comprises right-hand-circular polarization and said second polarization comprises left-hand-circular polarization.

4. A base station (300) according to Claim 2 wherein said first and second receive antenna (322a-b) are adjacent receive antennas.

5. A base station (300) according to Claim 2 wherein said first antenna (322a) also defines a first transmit coverage area and transmits signalshaving said second polarization, and wherein said second antenna (322b) also defines a second transmit coverage area and transmits signals having said first polarization.

6. A base station (300) according to Claim 1 further comprising:
a third receive antenna (322c) defining a third receive coverage (356) are overlapping portions of said first and second receive coverage areas:
a third wideband receiver (332c) operatively connected to said third receive antenna (322c), wherein said third wideband receiver (322c) receives a third plurality of receive channels from said third receive coverage area (356) and wherein said third plurality of receive channels includes said atleast one common receive channel;
a third channel splitter (336c) operatively connected to said third wideband receiver (332c) for separating said third plurality of receive channels: and wherein said diversity combiner (338b) is operatively connected to said first, second, and third channel splitters (336a-c) for combining said common receive channel from said first, second, and third channel splittersto produce and enhanced quality output receive channel.

7. A base station (300) according to Claim 1 wherein each of said receive channels operates on a predetermined frequency and said first and second pluralities of receive channels each comprise receive channels operating on consecutive predetermined frequencies.

8. A base station according to Claim 7 wherein said first wideband receiver (332a) receives said first plurality of receive channels operating on consecutive predetermined cellular frequencies ranging from f1, to fn, and wherein said second wideband receiver (332b) receives said second plurality of receive channels operating on consecutive predetermined cellular frequencies ranging from f2 to fn+1.

9. A base station (300) for communicating with at least one mobile station (358) in a cellular communications system, said base station (300) comprising a plurality of receive antennas (322) wherein each receive antenna isoriented to define a respective receive coverage area (352, 354, 356), and a support structure (318) for supporting said plurality of receive antennas (322) so that a first receive antenna (322a) defines a first receive coverage area (352), a second receive antenna (322b) adjacent said first receive antenna defines a second receive coverage area (354) overlapping a portion of said first receive coverage area, and a third receive antenna (322c) adjacent said second receive antenna defines a third receive coverage area (356) overlapping portions of saidfirst and second receive coverage areas, said base station (300) characterized by:
a first wideband receiver (332a) operatively connected to said first receive antenna (322a), wherein said first wideband receiver is adapted to receive a first plurality of receive channels from said first receive coverage area (352);
a second wideband receiver (332b) operatively connected to said second receive antenna (322b), wherein said second wideband receiver is adapted to receive a second plurality of receive channels from said second receive coveragearea (354);
a third wideband receiver (332c) operatively connected to said third receive antenna (322c), wherein said third wideband receiver is adapted to receive a third plurality of receive channels from said third receive coverage area (356) and wherein said first, second, and third pluralities of receive channels include at least one common receive channel;

first, second, and third channel splitters (336a-c) operatively connected to said respective first, second, and third wideband receivers (332a-c) for separating said first, second, and third pluralities of receive channels; and a diversity combiner (338b) operatively connected to said first, second, and third channel splitters (336a-c) for combining said common receive channel from said first, second, and third channel splitters to produce an enhanced quality output receive channel.

10. A base station (300) according to Claim 9 wherein first and third receive antenna (322a, 322c) receive signals having a first polarization and said second receive antenna (322b) receives signals having a second polarization different from said first polarization, and wherein said diversity combiner (338b) comprises a polarization diversity combiner.

11. A base station (300) according to Claim 10 wherein said first and third antennas (322a, 322b) define respective first and third transmit coverage areas and transmit signals having said second polarization, and wherein said second antenna (322b) defines a second transmit coverage area and transmits signals having said first polarization.

12. A base station (300) according to Claim 10 wherein said first polarization comprises right-hand-circular polarization and said second polarization comprises left-hand-circular polarization.

13. A base station (300) according to Claim 9 wherein each of said receive channels operates on a predetermined frequency and said first, second, and third pluralities of receive channels each comprise receive channelsoperating on consecutive frequencies.

14. A base station according to Claim 13 wherein said first wideband receiver (332a) receives said first plurality of receive channels operating consecutive predetermined frequencies ranging from f1 to f n, wherein said second wideband receiver (332b) receives said second plurality of receive channels operating on consecutive predetermined frequencies ranging from f2 to fn+1, and wherein said third wideband receiver (332c) receives said third plurality of receive channels operating on consecutive predetermined frequenciesranging from f3 to fn+2,

15, A method for communicating with at least one mobile station (350) in a communications system defining first and second receive coverage areas (352, 354) wherein said second receive coverage areas (354) overlaps a portion of said first receive coverage area (352), said method characterized by:receiving a first plurality of receive channels from the first receive coverage area (352);
receiving a second plurality of receive channels from the second receive coverage area (354), wherein said first and second pluralities ofreceive channels include at least one common receive channel;
separating said common receive channel from each of said first and second pluralities of receive channels; and combining said common receive channel from said first and second receive coverage areas (352, 354) to produce an enhanced quality output receive channel.

16. A method according to Claim 15 wherein said step of receiving said first plurality of receive channels comprises receiving said first plurality of receive channels having a first polarization, and wherein said step of receiving said second plurality of receive channels comprises receiving said second plurality of channels having a second polarization different from said first polarization.

17. A method according to Claim 16 wherein said first polarization comprises right-hand-circular polarization and said second polarization comprises left-hand-circular polarization.

18. A method according to Claim 16 further comprising the steps of:
transmitting signals having said second polarization into said first receive coverage area: and transmitting signals having said first polarization into said second receive coverage area.

19. A method according to Claim 15 further comprising the steps of:
receiving a third plurality of receive channels from a third receive coverage area (356) which overlaps portions of said first and second receive coverage areas (362, 354), and wherein said third plurality of receive channels includes said at least one common receive channel;
separating said third plurality of receive channels; and wherein said combining step further comprises combining said common receive channel from said first, second, and third channel splitters.

20. A method according to Claim 15 wherein each of said receive channels operates on a predetermined frequency and said first and second pluralities of receive channels each comprise receive channels operating on consecutive predetermined frequencies.

21. A method according to Claim 20 wherein said first plurality of receive channels operate on consecutive predetermined frequencies ranging from f1 to fn, and wherein said second plurality or channels operate on consecutive predetermined frequencies ranging from f2 to fn+1.