Abstract:
An omni-radio base station with multiple sector antenna units uses frequency division of sector signals to achieve increased coverage or capacity at reduced cost. Each sector antenna unit has an antenna for receiving a carrier signal associated with an antenna frequency in an available frequency band. At least one of the antenna units has an associated frequency converter that converts the carrier signal received by that antenna unit from the antenna frequency to a different respective frequency. Even though each sector receives the same carrier signal, an output carrier signal associated with each sector is at a different frequency band. A combiner combines the antenna unit carrier signals at different frequencies to create a composite signal for communication to the omni-radio base station. Because the antenna unit signals combined are at different frequencies, they do not interfere as much as they would if they were at the same antenna frequency, which results in less signal loss and degradation in the combiner. The carrier signals are then restored in the base station transceiver from the different respective frequencies to intermediate frequency for further processing.

Description:
RELATED APPLICATION 
       [0001]    This application claims the priority and benefit of U.S. Provisional patent application 60/761,782, filed Jan. 25, 2006, which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The technical field relates to multi-sector radio base stations. In one non-limiting example application, the technology described here may be used in an omni base station that is coupled to a multi-sector antenna system. 
       BACKGROUND 
       [0003]    An omni-base station is a base station that is configured to use an omni-antenna, and a sector base station is configured to use multiple (two or more) sector antennas.  FIG. 1A  shows a single cell area for a base station (BS) with an omni-antenna. An omni-antenna radiates 360 degrees to provide coverage over the entire cell area.  FIG. 1B  shows single cell area for a base station (BS) with three sector antennas. A three sector base station is a common sector configuration, but more or less sectors could be used. In this case, the cell area is divided into thirds, with each sector antenna having a narrower beam (as compared to an omni-antenna) that radiates to provide coverage over its sector area of approximately 120 degrees. 
         [0004]    A base station antenna is often mounted in an elevated location, such as on a tower, a pole, on the top or sides of buildings, etc., to enhance coverage and provide better possibilities for direct radio signal propagation paths.  FIG. 2A  shows a base station unit  14  located at the base of a tower  12 . An antenna  10  is mounted on the top of the tower  12  and is coupled via a feeder cable  16 , typically a coaxial cable or the like, to the base station transceiver. The received signal suffers signal losses traversing the feeder  16 , and the taller the tower  12 , the longer the feeder, and the greater the loss. In order to offset such signal losses in the feeder, a tower-mounted amplifier (TMA) may be used to amplify the received signal before it is sent over the feeder to the base station unit.  FIG. 2B  shows a TMA  18  mounted at the top of the tower  12  near antenna  10 . A tower mounted unit is sometimes called a mast head amplifier. The term tower mounted amplifier (TMA) is used generically herein to include any device that performs this pre-feeder amplification function. 
         [0005]      FIG. 3  shows a simplified block diagram of an omni-base station  20 . The antenna  10  is coupled to a duplex filter  21  in the TMA  18  which includes a receive (Rx) filter  22  and a transmit (Tx) filter  24 . The duplex filter makes it possible to send and receive on the same antenna by separating the Tx and Rx signals from each other. The transmit filter  24  is coupled directly to the feeder  16 , and the receive filter  22  is coupled to the feeder  16  via a low noise amplifier (LNA)  26 . The feeder  16  couples to the base station  14  which also includes a duplex filter  28  having a receive filter (Rx)  30  and a transmit (Tx) filter  32 . The transmit filter  32  is coupled to the transceiver  36 , and the receive filter  30  is coupled to the transceiver  36  via a low noise amplifier  34 . 
         [0006]    Antenna diversity may be used in order to improve reception (or transmission) of transmitted radio signals. There are many kinds of diversity, such as time diversity, space diversity, and combinations thereof. A promising diversity scheme uses time/space coded signals and is referred to as Multiple Input Multiple Output diversity (MIMO). Space diversity reduces the effects of fading received radio signals. An antenna diversity systems comprises at least two antennas arranged at a distance from each other. In the case of receive diversity, the received signal is received on the two or more antennas. The Rx signals from the diversity antennas are subjected to diversity processing in order to obtain an enhanced signal. Diversity processing may, for example, include selecting the antenna signal which is strongest, or adding the signals and further processing the resulting signal. In transmitter diversity, the transmit TX signal is transmitted on the two or more transmit antennas to which the transmitter is connected. Antennas of a diversity arrangement are called diversity antennas. In diversity arrangements, a feeder and its associated antenna may be referred to as a diversity branch or simply branch. 
         [0007]      FIG. 4  shows an example of an omni-base station  14  with diversity. Two diversity antennas  10   a  and  10   b  are coupled to corresponding TMAs  18   a  and  18   b . Each TMA is coupled by a corresponding feeder  16   a  and  16   b  to a corresponding duplex filter and low noise amplifier unit  42   a  and  42   b  in the base station  14 . The two duplex filter and LNA units  42   a  and  42   b  are coupled to a single transceiver  36 . 
         [0008]    In contrast to the single transceiver used in the omni-base station, a sector base station such as that shown at  50  in  FIG. 5  has a separate transceiver for each sector. Three sectors are supported with each sector having its own antenna  10   1 ,  10   2 , and  10   3 . Each of the antennas  10   1 ,  10   2 , and  10   3  is coupled to a corresponding sector TMA  18   1 ,  18   2 , and  18   3 . Three feeders  16   1 ,  16   2 , and  16   3  couple respective TMAs  18   1 ,  18   2 , and  18   3  to corresponding base station units  14   1 ,  14   2 , and  14   3 . Each of the base station units  14   1 ,  14   2 , and  14   3  has a corresponding duplex filter and low noise amplifier unit  42   1 ,  42   2 , and  42   3 . A sector base station provides more coverage than an omni-base station but at higher monetary and power costs. 
         [0009]    Although omni-base stations are less complex and less expensive than sector base stations, they also provide less coverage, and therefore, an operator must install more omni-base stations to cover a particular geographic area than if sector base stations were installed. In response, multi-sector omni-base stations were introduced where an omni-base station is coupled to a multi-sector antenna system. In fact, in an example where a three sector antenna system is used with an omni-base station, the three sector antenna system adds approximately 7-8 dB of signal gain. Another benefit of a multi-sector omni-base station is the ability to “tilt”, e.g., downtilt, one or more of the sector antennas. Tilting is not an option for omni antennas. 
         [0010]    An example of a three sector base station  60  is shown in  FIG. 6A . Three sectors are supported with each sector having its own antenna  10   1 ,  10   2 , and  10   3 . Each of the antennas  10   1 ,  10   2 , and  10   3  is coupled to a corresponding sector TMA  18   1 ,  18   2 , and  18   3 . Three feeders  16   1 ,  16   2 , and  16   3  couple respective TMAs  18   1 ,  18   2 , and  18   3  to the base station  14 . The base station  14  includes three duplex filter and low noise amplifier units labeled generally at  42  coupled to three transceivers  36 . But because feeder cables, duplex filters, and transceivers are expensive, (even more so when diversity is used in each sector), a splitter/combiner is used so that only one feeder is necessary.  FIG. 6B  shows how the received signals from the three sectors  1 ,  2 , and  3  are combined together in a splitter/combiner  44  onto one feeder cable  16 . In the transmit direction, the transmit signal is split into three identical signals (at lower power) and provided to each sector&#39;s TMA. 
         [0011]    But the feeder cost savings attained by using a splitter/combiner is offset by the substantial power lost in the combiner. Indeed, in the three sector example mentioned above, the 7-8 dB gain achieved by using a three sector antenna system is offset by 5 dB lost in the combiner. That loss is attributable to the interference between the three sector receive signals caused when they are combined in the combiner. That frequency overlap interference significantly reduces the signal-to-noise ratio of the sector signals received in the base station transceiver. The power is split to three different sectors in the splitter for the downlink transmission at 5 dB (i.e., one third) less power for each sector. One approach available to deal with the downlink transmission loss is to simply increase the base station transmit power. But substantially increasing the mobile station transmission power levels across the board is not an option in the uplink because transmit power of mobile stations generally must be tightly controlled and limited. 
       SUMMARY 
       [0012]    An omni-radio base station with multiple sector antenna units uses frequency division of sector signals to achieve increased coverage or capacity at reduced cost. Each sector antenna unit is coupled to an antenna for receiving a carrier signal associated with an antenna frequency in an available frequency band. The term “frequency band” includes a single frequency as well as a range of frequencies. A frequency converter in the antenna unit converts the carrier signal received by one of the multiple antenna units from that antenna frequency to a different respective frequency. A narrowband filter filters out a part of the available frequency band of interest. More than one frequency converter may be employed. A combiner combines carrier signals associated with each multiple antenna units to create a composite signal for communication to the omni-radio base station. At least two of the carrier signals associated with the multiple antenna units and combined in the combiner are received by receiving circuitry in the omni-base station at a different frequency. 
         [0013]    Depending on the implementation, the number of multiple sector antenna units having a corresponding frequency converter may be less than the number of multiple sector antenna units or the same. The combiner may combine carrier signals associated with each of the multiple antenna units to create a composite signal in which all of the carrier signals combined are associated with a different frequency band or in which only some of the carrier signals to be combined are at a different frequency. 
         [0014]    In one non-limiting example embodiment, each frequency converter includes a first local oscillator (LO) for providing a first LO frequency signal, and a first mixer frequency converts one of the sector carrier signals using the first LO frequency signal into an intermediate frequency (IF) signal. A narrowband filter filters the frequency converted output. A second local oscillator provides a second LO frequency signal corresponding to the respective frequency band, and a second mixer mixes the second LO frequency signal and the intermediate frequency signal to generate a frequency converted output. A narrowband filter or broadband filter (depending on the selectivity in the IF filter) filters the frequency converted output to the respective frequency band. Alternatively, the IF conversion need not be performed if there is a narrowband filer with enough selectivity after the conversion. 
         [0015]    A feeder coupled to the combiner transports the composite signal to a base station unit. Omni-base station receiving circuitry extracts each carrier signal corresponding to the multiple sector antenna units from the composite signal. The omni-base station receiving circuitry includes one or more base station mixers. Each base station mixer frequency converts a corresponding one of the respective carrier signals associated with a different frequency to an intermediate frequency for further processing. In a non-limiting three sector example, at least two base station mixers each receives a different local oscillator signal for extracting a different sector carrier signal. 
         [0016]    In one example implementation, one or more frequency converters is included in a corresponding one or more of the multiple antenna units. In another, the one or more frequency converters are included in the combiner. If there are multiple respective different frequency bands used as a result of the frequency conversion, those respective different frequency bands are distributed over the available frequency band. Preferably, those respective frequency bands are evenly distributed over the available frequency band. 
         [0017]    Diversity reception may be employed. For example, each sector may include a first diversity antenna unit and a second diversity antenna unit. One non-limiting example diversity implementation includes a first combiner for combining carrier signals associated with each of the first diversity antenna units to create a first composite signal for communication to the omni-radio base station, and a second combiner for combining carrier signals associated with each of the second diversity antenna units to create a second composite signal for communication to the omni-radio base station. A first feeder transports the first composite signal to the base station unit, and a second feeder transports the second composite signal to the base station unit. The base station unit extracts each of the diversity carrier signals corresponding to the multiple sector antenna units from the first and second diversity composite signals using one or more base station mixers. Each base station mixer frequency converts a corresponding one of the respective diversity carrier signals associated with a different frequency to an intermediate frequency for further processing. 
         [0018]    In another non-limiting example diversity implementation, a single combiner is used to combine carrier signals associated with each of the first and second diversity antenna units to create the composite signal for communication to the omni-radio base station. A splitter/combiner combines the sectors to one feeder cable. The single feeder then transports the composite signal including two frequencies for each sector to the base station receiver circuitry, which extracts each diversity carrier signal corresponding to the multiple diversity sector antenna units from the composite signal using one or more base station mixers. Each base station mixer frequency converts a corresponding one of the respective diversity carrier signals associated with a different frequency to an intermediate frequency for further processing. 
         [0019]    Frequency converting the signals received on at least one or more sector antenna units used with an omni-radio base station permits combiner loss normally encountered when sector signals are combined without frequency conversion. If all the signals in a three sector omni-radio base station combined are at different frequencies, then approximately a 5 dB power loss is avoided in the combiner. That way fewer feeder cables can be used without incurring a substantial loss in the combiner. Indeed, only a single feeder cable need be used in non-diversity as well as in diversity implementations. More efficient multi-sector omni-base stations are commercially attractive because coverage and/or capacity for omni-base stations can be increased using sector antennas. Indeed, existing omni-base stations can be easily upgraded to full coverage base stations using sector receive antennas and frequency conversion before combining and transmission to the base station transceiver over a feeder cable. Another advantage is that the power consumption is lower because less hardware is used. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1A  shows single cell area for a base station (BS) with an omni-antenna; 
           [0021]      FIG. 1B  shows single cell area for a base station (BS) with three sector antennas; 
           [0022]      FIG. 2A  shows a base station tower; 
           [0023]      FIG. 2B  shows a base station tower with tower-mounted amplifier (TMA); 
           [0024]      FIG. 3  shows a simplified block diagram of an omni-base station; 
           [0025]      FIG. 4  shows an example of an omni-base station with diversity; 
           [0026]      FIG. 5  shows an example of a sector base station; 
           [0027]      FIG. 6A  shows an example of a three sector base station; 
           [0028]      FIG. 6B  shows an example of a three sector omni-base station using a splitter/combiner and one feeder cable; 
           [0029]      FIG. 7  is a function block diagram of a non-limiting example embodiment of a multi-sector, omni-base station with reduced combiner loss; 
           [0030]      FIG. 8A  is a diagram of an available frequency band divided into subbands at the antennas for, e.g., an 850 MHz band; 
           [0031]      FIG. 8B  is a diagram showing an example where different sector signals are frequency-translated to a corresponding subband in the available frequency band on the feeder; 
           [0032]      FIG. 9A  is a diagram of a PCS frequency band divided into 5 MHz subbands; 
           [0033]      FIG. 9B  is a diagram of showing an example where three different sector signals are frequency translated to a corresponding subband in the PCS frequency band on the feeder; 
           [0034]      FIG. 10  is a flowchart outlining non-limiting example procedures for reducing combiner loss in a multi-sector, omni-base station; 
           [0035]      FIG. 11  is a function block diagram of another non-limiting example embodiment of a multi-sector, omni-base station with reduced combiner loss; 
           [0036]      FIG. 12  is a function block diagram of another non-limiting example embodiment of a multi-sector, omni-base station with reduced combiner loss; 
           [0037]      FIGS. 13A and 13B  are a function block diagram of another non-limiting example embodiment of a multi-sector, omni-base station with reduced combiner loss with diversity; and 
           [0038]      FIG. 14  is a function block diagram of yet another non-limiting example embodiment of a multi-sector, omni-base station with reduced combiner loss with diversity using just a single feeder. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    In the following description, for purposes of explanation and non-limitation, specific details are set forth, such as particular nodes, functional entities, techniques, protocols, standards, etc. in order to provide an understanding of the described technology. It will be apparent to one skilled in the art that other embodiments may be practiced apart from the specific details disclosed below. For example, while example embodiments are described in the context of multi-sector omni-radio base stations, the disclosed technology may also be applied to other types of multi-antenna devices and to indoor as well as outdoor applications. In other instances, detailed descriptions of well-known methods, devices, techniques, etc. are omitted so as not to obscure the description with unnecessary detail. Individual function blocks are shown in the figures. Those skilled in the art will appreciate that the functions of those blocks may be implemented using individual hardware circuits, using software programs and data in conjunction with a suitably programmed microprocessor or general purpose computer, using applications specific integrated circuitry (ASIC), and/or using one or more digital signal processors (DSPs). 
         [0040]      FIG. 7  is a function block diagram of a non-limiting example embodiment of a multi-sector, omni-base station  70  with reduced combiner loss. Although the term “multiple” is understood to mean two or more, in this non-limiting example, three sectors S 1 , S 2 , and S 3  are supported, with each sector having its own antenna  10   1 ,  10   2 , and  10   3 . Each of the antennas  10   1 ,  10   2 , and  10   3  is coupled to a corresponding sector antenna unit referred to in a non-limiting way as a tower mounted amplifier (TMA)  18   1 ,  18   2 , and  18   3 . The three TMAs  18   1 ,  18   2 , and  18   3  are connected to a splitter/combiner  62  so that only one feeder  16  is needed to couple the TMA received signals to an omni-base station  14  which includes a single duplex filter and low noise amplifier unit  42  which includes a receive filter  30  and a low noise amplifier  34 . For simplicity, the transmit path has been omitted. Each TMA includes a receive (Rx) filter  72   1 ,  72   2 , and  72   3  coupled to its respective antenna  10   1 ,  10   2 , and  10   3 . 
         [0041]    Each receive filter  72   1 ,  72   2 , and  72   3  is coupled to a respective amplifier  74   1 ,  74   2 , and  74   3 , and the amplified output is coupled to a corresponding mixer  76   1 ,  76   2 , and  76   3  where it is mixed with a frequency translating signal generated for example by a local oscillator  78   1 ,  78   2 , and  7   83 . In one non-limiting example, the frequency translating signal is different for each sector so that each sector signal is converted to a different frequency. Each mixer&#39;s output is filtered using a respective narrowband (NB) or bandpass filter  80   1 ,  80   2 , and  80   3  centered on the respective frequency to remove other mixer products as well as noise and interference from other parts of the available band. 
         [0042]    Although each sector signal is shown as frequency translated for the benefit of description only, one or more of the sector signals may not be frequency converted. Preferably, each sector signal is at a different frequency before being combined and transported to the omni-radio base station transceiver unit. In this three sector example, two of the sector signals could be frequency translated to different frequencies while the third sector signal is not frequency translated. In that case, the three sector signals are still at a different frequencies. The different frequencies are identified as f 1 , f 2 , and f 3 . In a less optimal example implementation, some of the sector signals are at different frequencies but two or more sector signals remain at the same frequency. This implementation is less optimal because the signals at the same frequency interfere and the signal-to-noise ratio is reduced in the combiner. 
         [0043]    Although not necessary, it may be desirable to frequency convert the combined signal to a different frequency, e.g., lower frequency, before transmitting the combined signal over the feeder  16 . For example, converting the combined signal to a much lower frequency can minimize loss in the feeder  16  and thus further reduce noise. 
         [0044]    At the base station  14 , the feeder  16  connects to a duplex filter unit  42  of which only the receive filter  30  and LNA  34  are shown. The duplex filter unit  42  is connected to an omni-base station receiver, only part of which is shown and includes mixers  82   1 ,  82   2 , and  82   3 . Normally, the multi-sector, omni-base station receiver would use one mixer at this stage followed by a narrowband filter to downconvert the received radio signal. But because each of the sector receive signals in this example is at a different frequency, three different local oscillator signals LO 1 , LO 2 , and LO 3  are mixed with composite signal from the combiner  62 . Local oscillators  84   1 ,  84   2 , and  84   3  provide those three different local oscillator signals LO 1 , LO 2 , and LO 3 . Each output is then filtered in a narrowband intermediate frequency (IF) filter  86   1 ,  86   2 , and  86   3  to produce a corresponding sector receive signal Rx 1 , Rx 2 , and Rx 3 . These sector receive signals Rx 1 , Rx 2 , and Rx 3  are then ready for further processing. 
         [0045]    To help explain the frequency translation, an example is now described in conjunction with  FIGS. 8A and 8B .  FIG. 8A  is a diagram of an available antenna frequency band divided into subbands A-E. However, subband B is the frequency band used by the omni-radio base station.  FIG. 8B  is a diagram showing an example where the three different sector signals all received in the used subband B are frequency translated to a corresponding subband in the available frequency band for the feeder: subbands A, C, and E are used. Although one of the sector signals need not be frequency translated and could remain in the used subband B, in this case, it is not desirable because there would be no guardband. Having a guard band reduces the chance of interference between the sector carrier signals. 
         [0046]    A real world example in the Personal Communication Services (PCS) band is now described in conjunction with  FIGS. 9A and 9B .  FIG. 9A  is a diagram of antenna frequencies for the PCS frequency band from 1850-1910 MHz divided into twelve 5 MHz subbands A 1 , A 2 , A 3 , D, B 1 , B 2 , B 3 , E, F, C 1 , C 2 , and C 3 . The used subband by the radio base station is the 5 MHz D band from 1865-1870 MHz. For the three sector example, the three different sector signals all received in the used subband D are frequency translated to a corresponding feeder subband frequency in the available frequency band, which in this example are A 1 , B 3 , and C 3  as shown in  FIG. 9B . However, one of the sector signals need not be frequency translated and could remain in the used subband D and there would still be a guard band separating the three sector signals. 
         [0047]    In this non-limiting example, the receive filters  72   1 ,  72   2 , and  72   3  each pass the available 60 MHz frequency band from 1860-1910 MHz. But the base station is only using the 5 MHz “D” subband from 1865-1870 MHz. The first sector received signal is frequency shifted to the Al subband using an LO 1  signal set at 15 MHz (1865-1850=15) and a NB filter 1  passing frequencies between 1850-1855 MHz. The second sector received signal is frequency shifted to the B 3  subband using an LO 2  signal set at 15 MHz (1880-1865=15) and a NB filter 2  passing frequencies between 1880-1885 MHz. The third sector received signal is frequency shifted to the C 3  subband using an LO 3  signal set at 40 MHz (1905-1865=40) and a NB filter 3  passing frequencies between 1905-1910 MHz. 
         [0048]    The frequency multiplexed signal carrying the three sector carriers at three different frequency bands A 1  (1850-1855), B 3  (1880-1885), C 3  (1905-1910) over the feeder  16  is processed by the omni-base station receiving circuitry. The received signal is filtered using the receive filter  30  which passes the 60 MHz wide PCS band from 1850-1910 MHz. After amplifying the filtered signal in the LNA  34 , the amplified received signal is sent to three mixers  82   1 ,  82   2 , and  82   3 , one in this example for each sector where the sector signal was frequency converted before sending it over the feeder  16 . The purpose of the receiving circuitry shown is to convert each sector signal to the same intermediate frequency (IF) signal. IF downconversion simplifies filtering and facilitates later baseband processing. To accomplish conversion to an IF of 200 MHz, the LO 1 , is set to 1652.5 MHz; the LO 2  is set to 1682.5 MHz; and LO 3  is set to 1707.5 MHz. In this non-limiting example, the 200 MHz output from mixer  82   1  is then filtered by each of the three 5 MHz NB filter  86   1 ,  86   2 , and  86   3  to pass frequencies from 197.5-202.5 MHz (centered around the 200 MHz IF). 
         [0049]      FIG. 10  is a flowchart outlining non-limiting example procedures for reducing combiner loss in a multi-sector, omni-base station. In step S 1 , each of the multiple sector antenna units receives a carrier signal associated with an antenna frequency in an available frequency band. The carrier signal received by one of the multiple antenna units is frequency converted from the antenna frequency to a respective frequency different from the antenna frequency band and narrowband filtering (step S 2 ). The carrier signals associated with each of the multiple antenna units are combined to create a composite signal for communication to the omni-radio base station (step S 3 ). At least two of the carrier signals associated with the multiple antenna units and combined in the combiner are at a different frequency. The composite signal is transported over a feeder to a base station unit (step S 4 ). Each carrier signal is extracted from the composite signal including frequency converting at least one carrier signal associated with a different frequency to an intermediate frequency for further processing (step S 5 ). 
         [0050]      FIG. 11  is a function block diagram of another non-limiting example embodiment of a multi-sector, omni-base station  90  with reduced combiner loss. This embodiment is similar to that in  FIG. 7  except that the frequency conversion is performed in the combiner  63  instead of the antenna units. Alternatively, three antennas could be coupled to one TMA unit that includes three receive filters, three LNAs, three frequency converters, three narrowband filters, and one combiner coupled to one feeder. 
         [0051]      FIG. 12  is a function block diagram of another non-limiting example embodiment of a multi-sector, omni-base station  92  with reduced combiner loss in which the frequency conversion includes an intermediate frequency (IF) conversion, narrowband filtering, and conversion to RF in approximately the available frequency band but on a different frequency. The reasons an IF conversion may be employed first before performing the frequency conversion to separate the sector signals in frequency before combining include: (a) IF-filters are more effective than RF-filters, (b) IF down-conversion and up-conversion are better known techniques than RF-RF conversions, and (c) the feeder frequencies may be located where desired in the available frequency band. The mixers and the local oscillators in the base station down-convert the different frequencies to IF for further processing. 
         [0052]      FIGS. 13A and 13B  are a function block diagram of another non-limiting example embodiment of a multi-sector, omni-base station  94  with reduced combiner loss and with diversity. Each sector TMA  18   1 ,  18   2 , and  18   3  includes two diversity receive branches A and B, although more than two diversity branches may be used if desired. For simplicity, transmit paths have been omitted. Each TMA includes a receive (Rx) filter  72   1A ,  72   2A , and  72   3A  coupled to a respective first antenna  10   1A ,  10   2A , and  10   3A  as well as a receive (Rx) filter  72   1B ,  72   2B , and  72   3B  coupled to a respective second antenna  10   1B ,  10   2B , and  10   3B . 
         [0053]    Each receive filter in the first diversity branch is coupled to a respective amplifier  74   1A ,  74   2A , and  74   3A , and each receive filter in the second diversity branch is coupled to a respective amplifier  74   1B ,  74   2B , and  74   3B . The amplified output for each of the first branches is coupled to a corresponding first mixer  76   1A ,  76   2A , and  76   3A , generated for example by a respective sector local oscillator  78   1 ,  78   2 , and  78   3 . The amplified output for each of the second branches is coupled to a corresponding second mixer  76   1B ,  76   2B , and  76   3B , where it is mixed with a frequency translating signal generated for example by the same respective sector local oscillator  78   1 ,  78   2 , and  78   3 . The frequency translating signal in this non-limiting example is different for each sector so that the two diversity signals for each sector are converted to a frequency that is different form the other sector signals. Each mixer&#39;s output in the first diversity branch is filtered using a respective narrowband (NB) or bandpass filter  80   1A ,  80   2A , and  80   3A  centered on the respective frequency to remove other mixer products as well as noise and interference in the available band. Similarly, each mixer&#39;s output in the second diversity branch is filtered using a respective narrowband (NB) or bandpass filter  80   1B ,  80   2B , and  80   3B  centered on the respective frequency to remove other mixer products. The two narrowband filters in each sector are centered on the same respective frequency. 
         [0054]    The “A” diversity branch outputs from each sector are combined in a first combiner  62 A, and the “B” diversity branch outputs from each sector are combined in a second combiner  62 B. In this way, only one feeder  16 A is needed to couple the TMA received signals from the first diversity branches at different frequencies f 1A , f 2A , and f 3A  to an omni-base station  14 , and only one feeder  16 B is needed to couple the TMA received signals from the second diversity branches at different frequencies f 1B , f 2B , and f 3B  to the omni-base station  14 . 
         [0055]    The omni-base station unit  14  includes a first duplex filter and low noise amplifier unit  42 A for the first feeder  16 A and a second duplex filter and low noise amplifier unit  42 B for the first feeder  16 B. The output from the first duplex filter and low noise amplifier unit  42 A is connected to mixers  82   1A ,  82   2A , and  82   3A , and the output from the second duplex filter and low noise amplifier unit  42 B is connected to mixers  82   1B ,  82   2B , and  82   3B . The output from the single local oscillator LO 1    84   1  is mixed with the inputs to mixers  82   1A  and  82   1B  to convert those signals to an IF or other desired frequency (e.g., baseband as in a homodyne) for respective filtering at  86   1A  and  86   1B  to produce diversity received signals Rx 1A  and Rx 1B  from sector  1 . The output from the single local oscillator LO 2    84   2  is mixed with the inputs to mixers  82   2A  and  82   2B  to convert those signals to an IF or other desired frequency for respective filtering at  86   2A  and  86   2B  to produce diversity received signals Rx 2A  and Rx 2B  from sector  2 . The output from the single local oscillator LO 3    84   3  is mixed with the inputs to mixers  82   3A  and  82   3B  to convert those signals to an IF or other desired frequency (e.g., baseband as in a homodyne) for respective filtering at  86   3A  and  86   3B  to produce diversity received signals Rx 3A  and Rx 3B  from sector  3 . 
         [0056]      FIG. 14  is a function block diagram of yet another non-limiting example embodiment of a multi-sector, omni-base station  96  with reduced combiner loss and with diversity using just a single feeder  16 . In this non-limiting example, there are three sectors S 1 -S 3 , and each sector includes two diversity antennas  10   A  and  10   B . Each diversity antenna has its own TMA (a respective one of  18   1A - 18   3B ) that generates in this example an output signal at a different frequency (a respective one f 1A -f 3B ). Those six different frequency carriers f 1A -f 3B  are combined in a single combiner  62  and transported to the omni-base station unit  14  over a single feeder  16 . Because each sector diversity signal is at a different frequency in this non-limiting example, they do not directly interfere in the combiner  62  or the feeder  16 . As compared to the example embodiment in  FIGS. 13A-13B , one less combiner and one less feeder are used, which saves on expense. A disadvantage though is that, depending on the size of the available frequency band allocated to the base station, there may be little or no guard band between each of the six TMA signals f 1A -f 3B . As a result, there may be added interference, and thus, reduced signal-to-noise ratio. In addition, only a single duplex receive filter  30  and LNA  34  are needed in the base station unit  14 , as compared to two in the example embodiment in  FIGS. 13A-13B . On the other hand, six (as compared to three) different local oscillators  84   1A - 84   3B  are needed to provide six different local oscillator signals LO 1A -LO 3B  to respective mixers  82   1A - 82   3B . 
         [0057]    Although various embodiments have been shown and described in detail, the claims are not limited to any particular embodiment or example. None of the above description should be read as implying that any particular element, step, range, or function is essential such that it must be included in the claims scope. The scope of patented subject matter is defined only by the claims. The extent of legal protection is defined by the words recited in the allowed claims and their equivalents. No claim is intended to invoke paragraph 6 of 35 USC §112 unless the words “means for” are used.