WO1999044297A2

WO1999044297A2 - Method and apparatus for a distributed base station antenna system

Info

Publication number: WO1999044297A2
Application number: PCT/US1999/003794
Authority: WO
Inventors: Jean Pierre Joseph Cole
Original assignee: Adicom Wireless, Inc.
Priority date: 1998-02-27
Filing date: 1999-02-22
Publication date: 1999-09-02
Also published as: AU2780299A; WO1999044297A3

Abstract

A multiple access radio communication system sends IF signals from individual radio modules (29) to separate dedicated antenna modules (77) in an antenna apparatus. Each antenna module (77) is dedicated to one radio module (29), and has RF circuitry for converting the frequency of the IF signals from the associated radio module (29). In a preferred embodiment an antenna module (77) has a radiating element mounted at a right angle to a reflecting base plate, and the RF circuitry for the associated antenna and radio module (29) is on a circuit board mounted parallel to the base plate opposite the radiating element. Antenna modules (77) may be stacked in vertical arrays, and vertical stacks may be arranged in different outwardly sector-radiating arrays. Also in a preferred embodiment, timing signals and power are provided to the RF circuitry at the antenna modules (77) on the respective coaxial cables (33, 35, 37, 39) serving each module.

Description

Method and Apparatus for a Distributed Base Station Antenna System

Field of the Invention

The present invention is in the field of multi-access radio communication and pertains more particularly to methods and apparatus for distributing amplification and antenna functions in such systems.

Background of the Invention

Wireless communication of all sorts is, at the time of this patent application, a rapidly expanding technology. Wireless communication functional innovations, such as Time Division Duplexing (TDD) systems and Frequency Division Duplexing (FDD) systems for sharing communication bands are well known, and much developmental effort is being expended to provide improvements to such systems. One application in which considerable development is being done is in the area of wireless local loop telephony systems, designed to deliver reliable telephone service to areas lacking adequate ground- line infrastructure.

A typical wireless local loop multiple-access communication system has a base station connected to a telephony switch via telephony trunks that are well known in the art. The base station has the ability of communicating via wireless broadcast with customer premises equipment CPE installed within range of the base station, as determined by location, broadcast power, antenna design and so on. Incoming events (telephone calls) are received by the base station and transmitted to client's phone systems (CPE) via wireless broadcast. Outgoing events (calls from clients) are transmitted to the base station, and then sent over telephony trunks to a connected telephone switch, and then on to their ultimate destinations over a public or private network. CPE at the client location typically comprises a telephone or equivalent communication device and hardware that is capable of sending and receiving radio signals to and from the base station as previously described.

In current art, in cases wherein multiple carriers employ a single antenna, the signals from the several carriers are separately modulated and amplified, then the signals are combined and a final amplification applied before the combined signals are applied to the antenna. The combined, amplified signal is carried between the base station and antenna over a low-loss coaxial cables adapted to carry the signal with minimal signal degradation. The low loss cables are deployed because of the high frequencies typically carried.

One of the drawbacks with the conventional apparatus and method is expense. For example, a single power amplifier (final amplification) in the base station must be designed to handle multiple RF carriers rated at maximum power without signal degradation or transmissions of spurious signals in other frequency bands. Maximum RF carrier output power levels are regulated by such organizations as the Federal Communications Commission (FCC) in the United States and the International Telecommunications Union (ITU) in Europe. Regulations imposed typically refer to the radiated power of each individual RF carrier. For maximum coverage in a particular area, each individual RF carrier is radiated at the maximum level allowed. Therefore, as the power levels and the number of RF carriers increase, such as would be the case if a system is being expanded for a larger area, then the cost of amplification rises dramatically.

Another problem with using a single power amplifier in the base station relates to possible failure of the system resulting in a service loss to the covered area. This is the "single point of failure" problem. To guard against possible failure of the primary amplifier, a second backup amplifier must be deployed. This requirement doubles the cost of already expensive hardware. Furthermore, additional amplifiers and antenna arrangements are required to utilize additional frequency bands when the system is a multi-band system. This is true because high-linearity, high-power (HLHP) power amplifiers of the type used in current art are only capable of operating on one narrow frequency band.

Yet another drawback presents itself by the fact that a high power amplifier cannot practically or conveniently be located at the antenna mast. Therefore, expensive low-loss type RF coaxial cables must be used to carry the signal to the amplifier and up the mast to the antenna.

Furthermore, a single antenna precludes the ability to sectorize an area multiplying individual channels to cover multiple sectors). Sectorization is an important technique used in increasing the capacity of a cellular system. What is clearly needed is a method and apparatus whereby the power requirements with regards to amplification and antenna function of a multi-access wireless communication system can be distributed, utilizing lower cost components requiring less power to operate. Such a system would dramatically lower the costs associated with the implementation and operation of current art systems, as well as providing a means for independent assignment of frequency and channel to simplify sectorization.

Summary of the Invention

In a preferred embodiment of the present invention a system for radio broadcasting is provided, comprising a base station having a radio module providing modulated output at Intermediate Frequency (IF); a coaxial cable connected to the radio for conducting the output of the radio module at IF frequency; and an antenna module remote from the base station, the antenna module having an RF circuit connected to the coaxial cable, the RF circuit including conversion circuitry adapted for converting the IF signal from IF frequency to RF frequency and a power amplifier adapted for amplifying the RF signal to broadcast power level, and a radiating antenna coupled to the RF circuit and adapted for radiating the amplified RF signal. The system may be adapted as a multiple access system which further comprises plural radio modules, each radio module connected to a separate coaxial cable connected to a separate antenna module, wherein the multiple antenna modules are assembled into a single antenna apparatus.

Also in preferred embodiments, systems are adapted for two way broadcast and receive by one of time-division duplex (TDD) or frequency division duplex (FDD) protocol. In these embodiments each RF circuit associated with an antenna module comprises timing elements and amplification elements adapted for broadcast and receive functions. Power and control signals are preferably provided from the base station to the antenna module on each coaxial cable for the antenna module connected to that cable.

In a preferred embodiment each separate antenna module comprises an antenna mounted at substantially ninety degrees to a reflecting plate and coupled to the associated RF circuit, and plural antenna modules are assembled one above another with the reflecting plates in a common plane, forming a directional antenna stack. Three antenna stacks may be mounted in a triangular arrangement, the planes of each stack radiating outward, such that the principal radiation direction of each stack differs from the principal radiation direction of each of the other two stacks by substantially 120 degrees. A preferred application of such systems is in wireless local loop telephone systems, wherein the radio modules are connected to telephony equipment.

In an alternative aspect of the invention a modular radio broadcast antenna is provided, comprising an RF circuit comprising IF to RF conversion circuitry and power amplification circuitry, an input port adapted for connecting to a coaxial cable delivering an IF signal, and an output port providing a power-amplified RF signal; a reflecting plate adapted for reflecting a radiated signal; and a radiating antenna element coupled to the output port and mounted at substantially ninety degrees to the reflecting plate, providing for a primary direction of radiation substantially perpendicular to the plane of the reflective plate. The RF circuitry is preferably mounted on a board parallel to and attached to the reflecting plate on a side of the reflecting plate opposite the radiating element. An outer enclosure including an electrically insulating radome around the radiating element and a protective cover over the RP circuitry protects the components of antennas from weather.

A modular stack is provided comprising two or more modular antenna units, wherein each modular antenna unit comprises an RF circuit comprising IF to RF conversion circuitry and power amplification circuitry, an input port adapted for connecting to a coaxial cable delivering an IF signal, and an output port providing a power-amplified RF signal; a reflecting plate adapted for reflecting a radiated signal; and a radiating antenna element coupled to the output port and mounted at substantially ninety degrees to the reflecting plate, providing for primary direction of radiation substantially peφendicular to the plane of the reflective plate. In this embodiment the modular antenna units are arranged in a vertical stack having the reflective plates substantially in a common plane. Three or more modular antenna stacks are, in one embodiment, assembled into a modular antenna unit wherein each antenna stack comprises a vertical stack of two or more modular antenna units, and the modular antenna unit comprises an RF circuit comprising IF to RF conversion circuitry and power amplification circuitry, an input port adapted for connecting to a coaxial cable delivering an IF signal, and an output port providing a power-amplified RF signal; a reflecting plate adapted for reflecting a radiated signal; and a radiating antenna element coupled to the output port and mounted at substantially ninety degrees to the reflecting plate, providing for a primary direction of radiation substantially peφendicular to the plane of the reflective plate. In this embodiment, in each stack, the modular antenna units are arranged in a vertical stack having the reflective plates substantially in a common plane, and wherein the three or more stacks are positioned in a triangular array with the primary directions of radiation of each stack directed outward.

Methods for practicing the invention are provided as well. Both apparatus and methods are taught in the disclosure following in sufficient detail to enable one of ordinary skill in the art to practice the invention.

The present invention provides a modular communication system at a lower cost than conventional multiple access systems, and in a manner that is more flexible and easier to maintain. Other advantages will be apparent to the skilled artisan by reviewing the teachings which follow.

Brief Description of the Drawing Figures

Fig.l is a system diagram of a base station facility and amplifier/antenna structure for a wireless communication system as is currently known in the art. Fig. 2 is a system diagram of a base station facility and a distributed amplifier/antenna system for a wireless communication system according to an embodiment of the present invention.

Fig. 3 is a system diagram of the communication system of Fig. 2 according to an embodiment of the present invention wherein the distributed antennae are stacked in a three-sided vertical array.

Fig. 4 is a block diagram illustrating RF circuitry in a distributed antenna according to an embodiment of the present invention.

Fig. 5 A is an isometric view of a stacked antenna array enclosed in a radome according to an embodiment of the present invention.

Fig. 5B is a section view through the antenna structure of Fig. 5 A taken along sectioning line BB of Fig. 5 A and viewed in the direction of the arrows according to an embodiment of the present invention.

Fig. 6 is a conceptual diagram showing broadcast direction and overlap in a sectorized cell architecture according to an embodiment of the present invention.

Fig. 7A is an example view of a mounting scheme for antennas according to an embodiment of the present invention.

Fig. 7B is an alternative example of a mounting scheme for antennas according to an embodiment of the present invention. Fig. 8 is an overhead view of a radome enclosed antenna cell with rotated antennae according to an embodiment of the present invention.

Description of the Preferred Embodiments

Fig. 1 is a system diagram of a base station and antenna arrangement in a wireless communication system, as is currently known in the art, wherein a base station 9 comprises a plurality of radio modules 11 a-d that are connected to a monolithic wide-band amplifier 15 via internal wiring through a transmit/receive T/R switch 13. Wide-band amplifier 15 performs the last stage of signal amplification to the combined RF signals from the several modules before application of the signal to antenna structure 16, as previously described in the background section. In this example and in examples to follow T/R switches are generally shown. The use of switches, cycled at the timing for transmit and receive time slices, is for time-division duplex (TDD) systems. For frequency-division duplex systems, wherein separate frequencies are employed for transmit and receive, the T/R switch is generally replaced with a duplexer. This convention and understanding applies generally to all examples which follow.

Antenna structure 16 comprises an antenna receiving function (Rx) 17 and an antenna transmission function (Tx) 19. Antenna functions Rx 17 and Tx 19 are accomplished typically through a common antenna, rather than separate antennas. Antenna structure 16 is monolithic in nature and is used to transmit RE signals to receivers at client locations installed within the range of the system.

Antenna structure 16, as well as wide-band amplifier 15 are HLHP components, as described above, meaning that one structure is responsible for the total function represented. For example, HLHP amplifier 15 is responsible for the final amplification of all outgoing signals. Antenna structure 16 is responsible for receiving and transmitting to all client stations located within the range of the system.

As described previously in the background section, current art wireless communication systems use HLHP amplifiers in amplification and signal transmit and receive functions. In doing so, the amplifiers involved have to be located at ground level, typically close to the individual radio modules, as described relative to Fig. 1. Therefore special hi-quality, low-loss coaxial cables such as outgoing coaxial cable 21 and incoming coaxial cable 23 are required to facilitate adequate communication delivery with minimal loss to and from antenna structure 16 and base station 9. This is primarily due to the fact that the amplified, combined signal is transmitted to and applied to the antenna at RF frequencies. Coaxial cables of this type are relatively expensive and bulky when compared to other types of coaxial cables that are designed to carry signals at lower frequency.

The inventor proposes a wireless communication system that utilizes a distributed architecture with respect to amplification and antenna function, thereby significantly reducing the costs related to installing and operating high powered monolithic components and associated high-frequency low-loss cables. The methods and apparatus of the present invention according to preferred embodiments are fully described below in sufficient detail to allow the skilled artisan to practice the invention.

Fig. 2 is a system diagram of a base station facility and distributed amplification antenna according to an embodiment of the present invention. Wireless communication system 25 comprises a base station 27 containing a plurality of radio modules 29 a-d, similar to the wireless communication system of Fig. 1, except that instead of using HLHP amplification and antenna components as is the case with current art, these functions are distributed in a form of a plurality of smaller, lower- cost components operating at lower frequency. For example, rather than using a single amplifier such as HPLP amplifier 15 of Fig. 1, the system of the present invention (25) uses a plurality of low-cost monolithic amplifiers that are installed at the antennae and connected to each radio module such as radio modules 29 a-d by low-cost intermediate frequency (IF) coaxial cables. Frequency conversion is performed by mixers in the radio modules so only low-frequency signals are applied to the low-cost IF cables.

As separate signals are transmitted to the antenna and amplified there, a plurality of two-way antennae sections 3 la-d are provided so that each radio module 29a-d has it's own dedicated antenna element and individual amplification. Separate IF coaxial cables represented herein by element numbers 33, 35, 37, and 39 connect antennae modules 31 a-d to radio modules 29 a-d as illustrated.

For TDD applications each monolithic amplifier such as low-cost monolithic amplifier 47 in this embodiment has two T/R switches installed therein instead of a single T/R switch such as T/R switch 13 of Fig. 1. This arrangement indicates the directing of signals through the different amplifier portions dedicated to transmission and reception of signals.

Using the innovative distributed apparatus and method of the present invention provides a distinct advantage over prior art systems in that the smaller components used are much less expensive to install and operate than the HLHP components used in current art systems. Similarly, cabling costs are much reduced with deployment of IF coaxial cabling instead of the high cost low-loss cables. For example, typical low loss coaxial cabling is typically in the range of $600.00 per 200 foot section as opposed to $50.00 per 200 foot section of an IF coaxial cable such as RG 58 coaxial. In addition to cost advantages, there are distinct functional advantages over the HLHP-type system that are detailed further below.

Fig. 3 is system diagram of communication system 25 of Fig. 2 according to an embodiment of the present invention wherein multiple antennae sections are shown arranged and stacked in a three-sided vertical array comprising an antenna cell. The inventor proposes this antenna stacking arrangement as one embodiment wherein mounting of the antennae can be accomplished on top of a tower or other structure, thereby allowing an unobstructed 360 degree field for reception and transmission. Other possible embodiments include a four-sided vertical array, and so on. In this particular embodiment three panels comprising individual antennae components and RF circuitry are positioned at approximately 120 degrees radially.

In the embodiment of Fig. 3 an antennae cell assembly 49 comprises three panels made up of multiple antennae elements 77 that are arranged vertically in each panel. Panel 51 contains 5 vertically-stacked antennae elements 77. Panels 55 and 53 each contain 5 identical similarly stacked antennae elements 77. It will be apparent to one with skill in the art that there may be more or fewer antennae 77 arranged in each panel without departing from the spirit and scope of the present invention. The fact that only 5 antennae are present in each panel is solely for the puφose of example. It will also be apparent to one with skill in the art that there may be more or fewer radio modules such as radio modules 29 a-d present in base station 27 without departing from the spirit and scope of the present invention. It is intended by the inventor that each radio module have it's own antenna element so that in actual practice of the present invention, there would be the same number of each component, although this relationship is not strictly required in all embodiments of the invention.

Low-cost monolithic amplifiers and supporting circuitry present in Fig. 2 are not shown in Fig. 3, however, in actual practice of the present invention, these are mounted to circuit boards at each individual antenna module 77 and should be assumed to be present in this embodiment. The bottom surface of antennae cell 49 acts as a mounting surface and interfacing surface for IF coaxial cables 33, 35, 37, and 39.

As previously described with reference to Fig. 2, there are certain advantages inherent in the method of the present invention other than cost reduction. For example, maintaining individual antennae for each radio module facilitates sectorization of a specific area to a specific module. A radio module such as module 29a is assigned a channel having a specific frequency band. Target CPE are assigned the same channel and may use one dedicated antenna for communication, and so on. Such assignments are made such that specific client's may be in a defined radial sector for one radio module, and may therefore be served with less power expenditure than in a random situation.. This modular arrangement, wherein each radio module has it's own antenna portion and amplification circuitry, is advantageous over previous "monolithic" systems in that failure of a single amplifier results in the loss of capacity in only one small service-sector. The inventor intends that individual components such as antennae, circuit boards, and the like be removable and replaceable modularly, promoting ease of maintenance. Also, because of the fact that each radio module is independent as described above, widely varying frequency bands may be used to transmit and receive with respect to different radio modules within the same base station. This is a marked improvement over prior art systems that are restricted to a narrow band of frequency due to amplifier requirements, or that have to use multiple amplifiers if widely disparate radio bands have to be used.

Because a smaller individual antenna is employed for each radio module, and amplification is distributed among low power amplifiers that can be mounted within the antenna assembly, radio frequency (RF) circuitry is rather simple when compared to RF circuitry associated with a HLHP amplifier such as HLHP amplifier 15 of Fig. 1. Furthermore, the cost of the smaller individual components used in communications system 25 is significantly less than the cost of deploying and maintaining a HLHP system.

Fig. 4 is a block diagram illustrating in a general way RF circuitry associated with one antenna according to an embodiment of the present invention, wherein lower power requirements associated with a smaller amplifier facilitate a simple architecture. In an embodiment of the invention RF circuitry is mounted on an PC board (not shown) that is mounted to the same metal frame as the antenna element. A connector known in the art as a blind mate RF connector completes the interface from an RF board to an antenna element or substrate.

A simple circuitry design incoφorates dual T/R switches (TDD) with T/R switch 64 at the base-station side of the RF circuitry and T/R switch 62 at the antenna side of the RF circuitry. This approach allows for two-way communication using a single antenna and a single IF cable. A band-pass filter 61 keeps outside or out-of- band signals from being transmitted and amplified. A low noise amplifier (LNA) 71 boosts the signal without adding additional significant noise. The signal passes through an image filter 72 and is amplified before being converted from RF to IF via a conversion mixer 69. An oscillator 67 is wired to mixer 69 and determines the IF frequency. The signal then travels to the base station. Outgoing signals utilize the lower half of the RF circuitry as follows: A conversion mixer 70 converts the signal from IF to RF. Then the signal is amplified before passing through an image filter 59. A signal driver 65 steps up the power level of the signal before final amplification via power amplifier 63. The signal then passes through band-pass filter 61 and on to the antenna module. Block 66 represents function that are multiplexed or otherwise imposed on each IF cable, and that are necessary for full operation of the distributed system in addition to the radio signals from each radio module in the base station. These functions include providing DC power to circuitry, control signals for switching functions, and status reporting such as load and frequency references. It will be apparent to one with skill in the art that various circuitry implementations known in the art may be utilized and provided without departing from the spirit and scope of the present invention. Fig. 4 is just one example. There are many other possible variations.

Fig. 5 A is an isometric view of a single vertically stacked antenna assembly enclosed within a radome according to an embodiment of the present invention, in an arrangement particularly suited for use in situations wherein the top of a tower or other structure offering an unimpeded 360 degree field for radiation is not available. One vertically stacked antenna panel such as antenna panel 51 in antenna cell 49 of Fig. 3 is shown enclosed within a radome 81 forming a complete antenna sector 73, three of which would comprise an antenna module 49 as illustrated in Fig. 1. As one component in a three-sided assembly, antenna sector 73 may be mounted separately on one side of a tower, or, antenna sector 73 may be integrated with two like sectors and enclosed within one radome forming a complete assembly that could be mounted in an unobstructed location such as on the top of a tower, etc. A case for mounting three separate antenna sectors such as antenna sector 73 to a side of a tower would present itself in the event that the top of that tower had existing apparatus mounted, thereby precluding a top-mounted antenna assembly.

A trunk 79 housing individual IF cables such as IF cable 37 of Fig. 3 interfaces with the bottom surface of antenna structure 73 with individual IF cables extending to and interfacing with assigned RF boards 75. In this example there are 5 separate antennae 77 arranged and vertically stacked as previously described with reference to Fig. 3. Radome 81 is provided for the puφose of enclosing and protecting internal components from weather damage and the like. Such protective enclosures are well known in the art and are constructed of such material as fiberglass. Fig. 5B is a section view of antenna sector 73 of Fig. 5 A according to an embodiment of the present invention taken along the sectioning line BB and viewed in the direction of the arrows. In this embodiment antenna element 77 is mounted to an aluminum frame 78 which in turn is mounted peφendicularly to (or as a part of) a reflective back plate 82. Antenna 77 may be of the form of a simple "dipole" that is etched into a low loss substrate material such as Teflon™ or other suitable low-loss material. RF board 75 comprises the RF circuitry as described with reference to Fig. 4. RF board 75 is positioned directly behind reflective back plate 82 and is mounted to the same aluminum frame to which antenna 77 is mounted. Radome 81 protects internal components from the weather. A rear cover 89 protects the RF board and mates with radome 81. The general direction of influence of antenna 77 is illustrated via directional arrows emanating from radome 81.

A blind-mate RF connector 83 (known in the art) forms an interface between RF board 75 and antenna 77. It will be apparent to one with skill in the art that other types of antenna structure, RF connect methods, and component positioning may be used without departing from the spirit and scope of the present invention. This embodiment illustrates one of many possible variations in antenna structure that may be used.

Fig. 6 is a radiation direction diagram according to an embodiment of the present invention. This diagram illustrates the general situation for a triangular modular distributed antenna according to the present invention as per Fig. 3. In such an arrangement there will be overlap areas as shown wherein signals may be corrupted (additive and subtractive effects, for example). The problem can be overcome by using a second assembly rotated 60 degrees from the first, so the principal radiation direction of the second antenna sectors encompasses the overlap areas as shown. This situation is described more fully below.

With one assembly (a three-sided vertically-stacked antenna array) mounted on a top surface of a tower structure, a 360 degree radius of service is provided to clients within the broadcast range of communications system 25 of Fig.2. However, because three separate groups of radio modules and antennae operating on a same frequency range are used to drive three 120 degree patterns within the 360 degree covered radius, there will invariably be situations wherein clients are physically located in an area marked as an overlap area. An overlap area is where the boundaries of two antenna merge. Reception in an overlap area can be plagued by excessive co- channel interference resulting from the influence of two separate antenna. Therefore a second cell operating at a different frequency range is installed on top of (or below) the fist cell in order to service the overlap areas created by the first cell.

Antenna structure 73 as illustrated in Fig. 5A would comprise one sector of a three-sector cell capable of producing three 120 degree patterns. Therefore, six sectors would comprise a complete antenna system that would be capable of covering the overlap areas with one three-sector cell stacked on top of the other. Shown in this example is a cell pattern 1 operating within frequency range A. Three overlap areas can be seen where the patterns overlap each other. A cell pattern 2 operating within frequency range B services the overlap areas created by cell pattern 1. Three overlap areas created by cell pattern 2 are in turn serviced by cell pattern 1.

There are a number of ways to solve co-channel interference problems in overlap areas without utilizing two complete assemblies as described in this embodiment. For example, antenna rotation may be utilized because of the innovative modular nature of individual antennae. Details of other embodiments wherein rotation of individual antennae is applied are described below. Fig. 7 is a simple example view of two different mounting scenarios for antenna structure according to an embodiment of the present invention

Space for mounting antenna for communications systems may not always be available to a communications provider as preferred. For example, a preferred location for mounting such radio antennae is at the top of a tower or structure that is high enough and positioned so that all customers may be adequately serviced. For this reason, the inventor has proposed different arrangement for mounting antenna structures according to embodiments of the present invention.

Fig. 7A illustrates a preferred mounting location at the top of a tower suited for the puφose. A three-sided vertically stacked cell 85 enclosed in a radome according to an embodiment of the present invention is mounted on the top surface of the tower. This provides an unobstructed 360 degree field of radiation to clients within range of cell 85. However, there are situations wherein existing apparatus may already be installed on the top surface of a tower. In this case, as shown in Fig. 7B, individual antenna sectors such as antenna sector 73 of Fig. 5 A may be separately enclosed in radomes and mounted at a position lower than the top and around the side of a tower so as to complete the 360 degree coverage as is shown in Fig. 7A.

As described with reference to Fig. 6, overlap areas may be addressed by stacking a second cell on top of a first cell. However, this may only be accomplished conveniently if the top of the tower can be utilized as in Fig. 7 A. If Fig. 7B is the prevalent situation, then overlap areas may be addressed in another way as described below.

Fig. 8 is an overhead view of a radome-enclosed antenna assembly according to an embodiment of the present invention wherein alternative antennae such as antenna 77 are rotated approximately 60 degrees relative to each other. This is an alternate method for addressing the overlap situation described with reference to Fig. 6 describing how cells are stacked on top of each other with one cell rotated. In this case, a complete antenna assembly such as assembly 85 is enclosed within radome 81 and mounted, preferably, atop a tower as described with reference to Fig. 6. However, instead of stacking a second cell that is operating at another frequency range as was done in the embodiment of Fig. 6, individual antenna are assigned to the different frequency range, and rotated 60 degrees to service the overlap. This can be accomplished by alternating rotation of the individual antenna such as antenna 77 down the panel. For example, the top antenna could be rotated to the right, the second one to the left, and so on. The antennae with the same side rotation would share the same frequency attributes.

The same rotation method applies in an instance such as Fig. 7B wherein separate sectors such as antenna structure 73 of Fig.5 A are side-mounted. As well, when side mounting individual sectors, sector pairs of differing frequency ranges may be mounted in one position and rotated 60 degrees away from each other so as to address overlap conditions with the need for rotating individual antennae.

It will be apparent to one with skill in the art that the method and apparatus of the present invention may be applied to a variety of wireless radio-communication systems without departing from the spirit and scope of the present invention such as cellular systems, various types of TDD and FDD wireless local-loop systems and the like.

For application of the present invention to FDD for example, duplexers would be used instead of Transmit/Receive switches with perhaps some minor adjustments in the RF circuitry related to component differences. An FDD system much like a TDD system uses the HLHP components attributed to prior and current art systems of both types thereby lending itself to the same advantages achieved with a TDD system according to various embodiments of the present invention.

It will also be apparent to one with skill in the art that a communication system such as communication system 25 of the present invention may operate on a wide variety of frequency ranges, and may be configured to a large number of channels within the frequency range without departing from the spirit and scope of the present invention. For example, due to the modular nature of the system as previously described and taught herein, individual radio modules and antennae may be independently set to specific frequency ranges and channels. Such an option has not been possible with prior art systems. The spirit and scope of the present invention is limited only by the claims that follow.

Claims

What is claimed is:

1. A system for radio broadcasting, comprising: a base station having a radio module providing modulated output at Intermediate Frequency (IF); a coaxial cable connected to the radio for conducting the output of the radio module at IF frequency; and an antenna module remote from the base station, the antenna module having an RF circuit connected to the coaxial cable, the RF circuit including conversion circuitry adapted for converting the IF signal from IF frequency to RF frequency and a power amplifier adapted for amplifying the RF signal to broadcast power level, and a radiating antenna coupled to the RF circuit and adapted for radiating the amplified RF signal.

2. The system of claim 1 adapted as a multiple access system and further comprising plural radio modules, each radio module connected to a separate coaxial cable connected to a separate antenna module, and wherein the multiple antenna modules are assembled into a single antenna apparatus.

3. The system of claim 2 adapted for two way broadcast and receive by one of time- division duplex (TDD) or frequency division duplex (FDD) protocol, wherein each RF circuit associated with an antenna module comprises timing elements and amplification elements adapted for broadcast and receive functions.

4. The system of claim 3 wherein power and control signals are provided from the base station to the antenna module on each coaxial cable for the antenna module connected to that cable.

5. The system of claim 2 wherein each separate antenna module comprises an antenna mounted at substantially ninety degrees to a reflecting plate and coupled to the associated RF circuit, and plural antenna modules are assembled one above another with the reflecting plates in a common plane, forming a directional antenna stack.

6. The system of claim 5 wherein three antenna stacks are mounted in a triangular arrangement, the planes of each stack radiating outward, such that the principal radiation direction of each stack differs from the principal radiation direction of each of the other two stacks by substantially 120 degrees.

7. The system of claim 3 adapted for use in a wireless local loop telephone system, the radio modules being connected to telephony equipment.

8. A modular radio broadcast antenna, comprising: an RF circuit comprising IF to RF conversion circuitry and power amplification circuitry, an input port adapted for connecting to a coaxial cable delivering an IF signal, and an output port providing a power-amplified RF signal; a reflecting plate adapted for reflecting a radiated signal; and a radiating antenna element coupled to the output port and mounted at substantially ninety degrees to the reflecting plate, providing for a primary direction of radiation substantially pe╧åendicular to the plane of the reflective plate.

9. The modular antenna of claim 8 wherein the RF circuitry is mounted on a board parallel to and attached to the reflecting plate on a side of the reflecting plate opposite the radiating element.

10. The modular antenna of claim 8 further comprising an outer enclosure, the outer enclosure including electrically insulating radome around the radiating element and a protective cover over the RF circuitry.

11. A modular antenna stack comprising two or more modular antenna units, wherein each modular antenna unit comprises: an RF circuit comprising IF to RF conversion circuitry and power amplification circuitry, an input port adapted for connecting to a coaxial cable delivering an IF signal, and an output port providing a power-amplified RF signal; a reflecting plate adapted for reflecting a radiated signal; and a radiating antenna element coupled to the output port and mounted at substantially ninety degrees to the reflecting plate, providing for primary direction of radiation substantially pe╧åendicular to the plane of the reflective plate; wherein the modular antenna units are arranged in a vertical stack having the reflective plates substantially in a common plane.

12. A modular antenna apparatus comprising three or more modular antenna stacks, each antenna stack comprising a vertical stack of two or more modular antenna units, wherein each modular antenna unit comprises: an RF circuit comprising IF to RF conversion circuitry and power amplification circuitry, an input port adapted for connecting to a coaxial cable delivering an IF signal, and an output port providing a power-amplified RF signal; a reflecting plate adapted for reflecting a radiated signal; and a radiating antenna element coupled to the output port and mounted at substantially ninety degrees to the reflecting plate, providing for a primary direction of radiation substantially pe╧åendicular to the plane of the reflective plate; and wherein, in each stack the modular antenna units are arranged in a vertical stack having the reflective plates substantially in a common plane, and wherein the three or more stacks are positioned in a triangular array with the primary directions of radiation of each stack directed outward.

13. A method for broadcasting on individual bands in a multiple access system, comprising steps of:

(a) providing a first modulated IF broadcast signal from a first radio module and a second IF broadcast signal from a second radio module in a base station; (b) conducting the first IF signal by a first coaxial cable to a first antenna module and the second IF signal by a second coaxial cable to a second antenna module; and

(c) converting the first IF signal to RF frequency and amplifying the first IF signal to broadcasting power at a first RF circuit associated with the first antenna module, providing a first power amplified RF broadcast signal;

(d) converting the second IF signal to RF frequency and amplifying the second IF signal to broadcasting power at a second RF circuit associated with the second antenna module, providing a second power amplified RF broadcast signal; (e) radiating the first power amplified RF signal by a first radiating element coupled to the first RF circuit; and

(f) radiating the second power amplified RF signal by a second radiating element coupled to the second RF circuit.

14. The method of claim 13 further comprising steps for receiving RF signals at the radiating elements and supplying the received signals to the RF circuitry for amplification and transport to the base station via the respective coaxial cables, wherein in the broadcasting and receiving steps timing elements provide for alternating broadcast and receive periods.

15. The method of claim 14 adapted for time-division duplex communication, wherein the timing elements are switching elements.

16. The method of claim 14 adapted for frequency division duplex communication, wherein the timing elements are duplexers.