Abstract:
A method may include reconfigurably enabling one of a first downconverter and a second converter and disabling the other the second downconverter, wherein the first downconverter and the second downconverter are integral to a receiver unit of as wireless communications terminal. The method may also include frequency downconverting received wireless communication signals by the enabled downconverter. The method may also include processing the downconverted wireless communication signals by a primary path if the first downconverter is enabled, and processing the downconverted wireless communication signals by a diversity path if the second downconverter is enabled.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to wireless communication and, more particularly, to a reconfigurable wireless diversity receiver. 
     BACKGROUND 
     In a wireless communication system, a transmitter modulates data onto a radio frequency (RF) carrier signal to generate an RF modulated signal that is more suitable for transmission. The transmitter then transmits the RF modulated signal via a wireless channel to a receiver. The transmitted signal may reach the receiver via one or more propagation paths (e.g., a line-of-sight path and/or reflected paths). The characteristics of the propagation paths may vary over time due to various phenomena such as fading and multipath. Consequently, the transmitted signal may experience different channel conditions and may be received with different amplitudes and/or phases over time. 
     To provide diversity against deleterious path effects, multiple antennas may be used to receive the RF modulated signal. At least one propagation path typically exists between the transmit antenna and each of the receive antennas. If the propagation paths for different receive antennas are independent, which is generally true to at least an extent, then diversity increases and the received signal quality improves when multiple antennas are used to receive the RF modulated signal. 
     A multi-antenna receiver conventionally has one RF receiver processing path (or simply, “receive path”) for each frequency band and each receive antenna. For example, if the multi-antenna receiver is designed to operate at two frequency bands (e.g., cellular and PCS bands), then it would normally have four receive paths for the two frequency bands for each of the two receive antennas. Each receive path includes various circuit blocks (e.g., amplifiers, filters, mixers, and so on) used to condition and process a received signal at a designated frequency band from an associated antenna. The circuit blocks are typically designed to meet various system requirements such as linearity, dynamic range, sensitivity, out-of-band rejection, and so on, as is known in the art. In conventional receiver designs, the receive path is often replicated for each frequency band of each of the receive antennas, with circuit modifications (as needed) for different frequency bands. The replication of the receive path circuitry results in higher cost, larger area, and higher power consumption for the multi-antenna receiver, all of which are undesirable. There is therefore a need in the art for a low-cost diversity receiver. 
     SUMMARY 
     In accordance with a particular embodiment of the present disclosure, a method may include reconfigurably enabling one of a first downconverter and a second converter and disabling the other the second downconverter, wherein the first downconverter and the second downconverter are integral to a receiver unit of as wireless communications terminal. The method may also include frequency downconverting received wireless communication signals by the enabled downconverter. The method may also include processing the downconverted wireless communication signals by a primary path if the first downconverter is enabled, and processing the downconverted wireless communication signals by a diversity path if the second downconverter is enabled. 
     In accordance with another particular embodiment of the present disclosure, a method may include frequency downconverting a first wireless communication signal by a first downconverter communicatively coupled to a primary path, the first downconverter integral to a first receiver unit of a wireless communications terminal and frequency downconverting a second wireless communication signal by a second downconverter communicatively coupled to a diversity path, the second downconverter integral to a second receiver unit of the wireless communications terminal. The method may further include configuring a switch to, when closed, communicatively couple an output of a second downconverter to the primary path, and, when open, isolate the output of the second downconverter from the primary path. The method may also include processing the downconverted first wireless communication signal by the primary path. The method may additionally include processing the downconverted second wireless communication signal by the diversity path if the switch is open, and processing the downconverted second wireless communication signal by the primary path if the switch is closed. 
     Technical advantages of one or more embodiments of the present invention may include a reconfigurable diversity receiver that requires less circuit area as compared to traditional approaches. 
     It will be understood that the various embodiments of the present invention may include some, all, or none of the enumerated technical advantages. In addition, other technical advantages of the present invention may be readily apparent to one skilled in the art from the figures, description and claims included herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a block diagram of an example wireless communication system, in accordance with certain embodiments of the present disclosure; 
         FIG. 2A  illustrates a block diagram of an example terminal having reconfigurable receiver diversity, in accordance with certain embodiments of the present disclosure; 
         FIGS. 2B-2D  each illustrate signal paths for various operational modes of the example terminal depicted in  FIG. 2A ; 
         FIG. 3A  illustrates a block diagram of another example terminal having reconfigurable receiver diversity, in accordance with certain embodiments of the present disclosure; 
         FIGS. 3B-3D  each illustrate signal paths for various operational modes of the example terminal depicted in  FIG. 3A ; and 
         FIG. 4  illustrates a block diagram of an example terminal having receiver diversity, as is known in the art. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a block diagram of an example wireless communication system  100 , in accordance with certain embodiments of the present disclosure. For simplicity, only two terminals  110   a  and  110   b  and two base stations  120   a  and  120   b  are shown in  FIG. 1 . A terminal  110  may also be referred to as a remote station, a mobile station, an access terminal, a user equipment (UE), a wireless communication device, a cellular phone, or some other terminology. Terminal  110   a  may be equipped with a single antenna, and terminal  110   b  may be equipped with two or more antennas. A base station  120  may be a fixed station and may also be referred to as an access point, a Node B, or some other terminology. A mobile switching center (MSC)  140  may be coupled to the base stations  120  and may provide coordination and control for base stations  120 . 
     A terminal  110  may or may not be capable of receiving signals from satellites  130 . Satellites  130  may belong to a satellite positioning system such as the well-known Global Positioning System (GPS). Each GPS satellite may transmit a GPS signal encoded with information that allows GPS receivers on earth to measure the time of arrival of the GPS signal. Measurements for a sufficient number of GPS satellites may be used to accurately estimate a three-dimensional position of a GPS receiver. A terminal  110  may also be capable of receiving signals from other types of transmitting sources such as a Bluetooth transmitter, a Wireless Fidelity (Wi-Fi) transmitter, a wireless local area network (WLAN) transmitter, an IEEE 802.11 transmitter, and any other suitable transmitter. 
     In  FIG. 1 , each terminal  110  is shown as receiving signals from multiple transmitting sources simultaneously, where a transmitting source may be a base station  120  or a satellite  130 . In general, a terminal may receive signals from zero, one, or multiple transmitting sources at any given moment. For multi-antenna terminal  110   b , the signal from each transmitting source is received by each of the multiple antennas at the terminal, albeit at different amplitudes and/or phases. 
     System  100  may be a Code Division Multiple Access (CDMA) system, a Time Division Multiple Access (TDMA) system, or some other wireless communication system. A CDMA system may implement one or more CDMA standards such as IS-95, IS-2000 (also commonly known as “1x”), IS-856 (also commonly known as “1xEV-DO”), Wideband-CDMA (W-CDMA), and so on. A TDMA system may implement one or more TDMA standards such as Global System for Mobile Communications (GSM). The W-CDMA standard is defined by a consortium known as 3GPP, and the IS-2000 and IS-856 standards are defined by a consortium known as 3GPP2. 
     System  100  may operate on one or more specific frequency bands. Table 1 lists various example frequency bands in which system  100  may operate. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Frequency Band 
                 Frequency Range 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Personal Communication System (PCS) 
                 1850 to 1990 
                 MHz 
               
               
                 Cellular 
                 824 to 894 
                 MHz 
               
               
                 Digital Cellular System (DCS) 
                 1710 to 1880 
                 MHz 
               
               
                 GSM900 
                 890 to 960 
                 MHz 
               
               
                 International Mobile 
                 1920 to 2170 
                 MHz 
               
               
                 Telecommunications - 2000 
               
               
                 CDMA450 
                 411 to 493 
                 MHz 
               
               
                 JCDMA 
                 832 to 925 
                 MHz 
               
               
                 KPCS 
                 1750 to 1870 
                 MHz 
               
               
                 GPS 
                 1574.4 to 1576.4 
                 MHz 
               
               
                   
               
             
          
         
       
     
     The PCS band may also be known as GSM1900, the DCS band may also be known as GSM1800, and the cellular band may also be known as an Advanced Mobile Phone System (AMPS) band. System  100  may also operate on a frequency band that is not listed in Table 1. 
     For each of the frequency bands listed in Table 1, one frequency range may be used for the forward link (i.e., downlink) from the base stations to the terminals, and another frequency range may be used for the reverse link (i.e., uplink) from the terminals to the base stations. As an example, for the cellular band, the 824 to 849 MHz range may be used for the reverse link, and the 869 to 894 MHz range may be used for the forward link. 
     A terminal may be a single-band terminal or a multi-band terminal. A single-band terminal (e.g., terminal  110   a ) supports operation on one specific frequency band (e.g., cellular or PCS). A multi-band terminal (e.g., terminal  110   b ) supports operation on multiple frequency bands (e.g., cellular and PCS) and typically operates on one of the supported bands at any given moment. A multi-band terminal can communicate with different wireless communication systems operating on different frequency bands. 
       FIG. 2A  illustrates a block diagram of an example terminal  200  having reconfigurable receiver diversity, in accordance with certain embodiments of the present disclosure. Terminal  200  may be used in a wireless communication system, such as system  100 , for example (e.g., terminal  200  may be used as a multi-antenna terminal  110   b  in system  100 ). Although embodiments of the present disclosure may include any suitable number of antennae and receiver units, the embodiment depicted in  FIG. 2A  includes two antennae  212   a  and  212   b  coupled to four receiver units  220   a - 220   d  via antenna switches  214   a  and  214   b . Antennae  212   a  and  212   b  may be formed in various manners at terminal  200  (e.g., with printed traces on a circuit board, wire conductors, and so on), as is known in the art. Each receiver unit  220  may process a received signal from one or more corresponding antennae  212  via an antenna switch  214  and provide a respective output baseband signal to either of a primary path  240  and a diversity path  250 . 
     Each receiver unit  220  may include one or more bandpass filters configured to receive a signal from a corresponding switch  214  pass signal components in the band of interest and remove out-of-band noise and undesired signals. In addition, each receiver unit  220  may include one or more low-noise amplifiers (LNAs)  224  to amplify a signal received via a corresponding antenna  212 . Some receiver units  220  (e.g., receiver units  220   a  and  220   b ) may include two or more ports  221  (e.g., bandpass filter  222 /LNA  224  combinations), and thus may receive signals via two or more bands. Other receiver units  220  (e.g., receiver units  220   c  and  220   d ) may include a single port, thus enabling receipt of signals via a single band. Each receiver unit  220  may also include at least two downconverters  230 : one downconverter  230  associated with primary path  240 , one downconverter  230  associated with diversity path  250 . Each downconverter  230  may be configured to frequency downconvert a wireless communication signal (e.g., a wireless communication signal received via an associated antennae  212  and amplified by associated LNAs  224 ) by an oscillator signal provided by an oscillator  236  and/or a quadrature signal provided by quadrature generator  238 . Oscillator  236  may be any suitable device, system, or apparatus configured to produce an analog waveform of a particular frequency for demodulation or downconversion of a wireless communication signal amplified by an LNA  224 . Quadrature generator  238  may be may be any suitable device, system, or apparatus configured to produce in-phase and quadrature signals for a downconverter  230  based on the received oscillator  236  signal. In operation, one of the two downconverters  230  of a receiver unit may be enabled such that a receiver unit  220  passes a downconverted signal to either primary path  240  or diversity path  250 . 
     Each of primary path  240  and diversity path  250  may include a filter  252  and an analog-to-digital converter (ADC)  254 . Each filter  252  may be configured to filter a downconverted wireless communication signal in order to pass the signal components within a radio-frequency channel of interest and/or to remove noise and undesired signals that may be generated by the downconversion process. Each ADC  254  may be receive an analog signal from an associated filter  252  and convert such analog signal into a digital signal. Such digital signal may then be passed to one or more other components of terminal  200 . 
     In some embodiments, primary path  240  may be configured to support numerous wireless communications bands (e.g., 2G, 3G, and 4G technologies), while diversity path  250  may be configured to support a subset of such bands (e.g., may not include support for 2 G communications technologies, but may include support for 3G and 4G technologies), thus allowing diversity path  250  to require less space (e.g., less circuit area) than if full support was present. In such embodiments, each port  221  and receiver  220  of terminal  200  may be able to support all of the bands supported by primary path  240 . This may permit reconfigurable diversity for terminal  200  while requiring less circuitry than traditional approaches to receiver diversity. 
       FIGS. 2B-2D  each illustrate signal paths for various operational modes of example terminal  200  depicted in  FIG. 2A . For example, arrows in  FIG. 2B  illustrate signal paths for when terminal  200  is in non-diversity mode. In such mode, all signals received in any communication band flow to primary path  240  without diversity. As another example, in diversity mode, terminal  200  may be configured such that signals received by some of receivers  220  are routed to diversity path  250 , while other signals are routed to primary path  240 , providing for receiver diversity, as shown in  FIG. 2C . In  FIG. 2D , terminal  200  is depicted in non-diversity mode with a secondary port routed to primary path  240 . 
       FIG. 3  illustrates a block diagram of another example terminal  300  having reconfigurable receiver diversity, in accordance with certain embodiments of the present disclosure. Example terminal  300  may be similar to example terminal  200  except that its architecture is different. As in example terminal  200 , terminal  300  may be used in a wireless communication system, such as system  100 , for example (e.g., terminal  300  may be used as a multi-antenna terminal  110   b  in system  100 ). Although embodiments of the present disclosure may include any suitable number of antennae and receiver units, the embodiment depicted in  FIG. 3  includes two antennae  212   a  and  212   b  coupled to four receiver units  220   f - 220   i . Antennae  212   a  and  212   b  may be formed in various manners at terminal  300  (e.g., with printed traces on a circuit board, wire conductors, and so on), as is known in the art. A receiver unit  220  may process a received signal from one or more corresponding antennae  212  and provide a respective output baseband signal to either of a primary path  240  and a diversity path  250 . 
     Each receiver unit  220  may include one or more low-noise amplifiers (LNAs)  224  to amplify a signal received via a corresponding antenna  212 . Some receiver units  220  (e.g., receiver units  220   f  and  220   h ) may include two or more ports  221  (e.g., baseband filter  222 /LNA  224  combinations), and thus may receive signals via two or more bands. Other receiver units  220  (e.g., receiver units  220   g  and  220   i ) may include a single port  221 , thus enabling receipt of signals via a single band. Each receiver unit  220  may also include a downconverter  230  and oscillator  236 , and such downconverter  230  and oscillator  236  may have functionality and/or design identical or similar to the downconverters  230  and oscillators  236  of terminal  200 , as described above with respect to  FIG. 2A . 
     Each of primary path  240  and diversity path  250  of terminal  300  may have functionality and/or design identical or similar to primary path  240  and diversity path  250  of terminal  200 , as described above with respect to  FIG. 2A . As in terminal  200 , in some embodiments of terminal  300 , primary path  240  may be configured to support numerous wireless communications bands (e.g., 2G, 3G, and 4G technologies), while diversity path  250  may be configured to support a subset of such bands (e.g., may not include support for 2 G communications technologies, but may include support for 3G and 4G technologies), thus allowing diversity path  250  to require less space (e.g., less circuit area) than if full support was present. In such embodiments, each port  221  and receiver  220  of terminal  300  may be able to support all of the bands supported by primary path  240 . This may permit reconfigurable diversity for terminal  200  while requiring less circuitry than traditional approaches to receiver diversity. 
     Terminal  300  may also include switch  310 . Switch  310  may be configured to be open when diversity is enabled, and closed when diversity is disabled. Accordingly, when open, switch  310  may permit signals received on ports  221   a ,  221   b , and  221   e  and conditioned by receiver units  220   f  and  220   g  to be passed to primary path  240 , while permitting signals received on antennae  221   c ,  221   d , and  221   f  and conditioned by receiver units  220   h  and  220   i  to be passed to diversity path  250 . On the other hand, when closed, switch may permit all signals received on ports  221  and conditioned by receiver units  220  to be passed to primary path  240 . 
       FIGS. 3B-3D  each illustrate signal paths for various operational modes of example terminal  300  depicted in  FIG. 3A . For example, arrows in  FIG. 3B  illustrate signal paths for when terminal  300  is in non-diversity mode. In such mode, all signals received in any communication band flow to primary path  240  without diversity. As another example, in diversity mode, terminal  300  may be configured such that signals received by some of receivers  220  are routed to diversity path  250 , while other signals are routed to primary path  240 , providing for receiver diversity, as shown in  FIG. 3C . In  FIG. 3D , terminal  300  is depicted in non-diversity mode with a secondary port routed to primary path  240 . 
     To further illustrate potential advantages of the reconfigurable receiver diversity provided by the present disclosure, reference is made to Table 2, which depicts three non-limiting examples of configurations of bands assigned to various antennae/ports of a terminal (e.g. terminal  200 , terminal  300 ). 
     
       
         
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Port 
                 Configuration 1 
                 Configuration 2 
                 Configuration 3 
               
               
                   
               
             
             
               
                 221a 
                 Band 4 Primary 
                 Band 4 Primary 
                 Band 4 Primary 
               
               
                 221b 
                 Band 2 Primary 
                 Band 2/PCS 
                 Band 2/PCS 
               
               
                 221c 
                 Band 4 Diversity 
                 Band 3/DCS 
                 Band 3/DCS 
               
               
                 221d 
                 Band 2 Diversity/PCS 
                 Band 4 Diversity 
                 Band 4 Diversity 
               
               
                 221e 
                 Band 5 Primary 
                 Band 5/GSM850 
                 Band 5 
               
               
                 221f 
                 Band 5 Diversity/ 
                 Band VIII/EGSM 
                 Band 5 Diversity/ 
               
               
                   
                 GSM850 
                   
                 GSM850 
               
               
                   
               
             
          
         
       
     
     To further illustrate certain advantages of the present disclosure, reference is made to Table 3, which depicts how analogous configurations to those set forth in Table 2 might be realized using traditional approaches. 
     
       
         
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Port 
                 Configuration 1 
                 Configuration 2 
                 Configuration 3 
               
               
                   
               
             
             
               
                 221a 
                 Band 4 Primary 
                 Band 4 Primary 
                 Band 4 Primary 
               
               
                 221b 
                 Band 2 Primary 
                 Band 2/PCS 
                 Band 2/PCS 
               
               
                 221c 
                 Band 4 Diversity 
                 Band 3 
                 Band 3 
               
               
                 221d 
                 Band 2 Diversity/PCS 
                 Band 4 Diversity 
                 Band 4 Diversity 
               
               
                 221e 
                 Band 5 Primary 
                 Band 5/GSM850 
                 Band 5 
               
               
                 221f 
                 Band 5 Diversity/ 
                 Band VIII 
                 Band 5 Diversity 
               
               
                   
                 GSM850 
               
               
                 Additional 
                   
                 DCS 
                 DCS 
               
               
                 Port 1 
               
               
                 Additional 
                   
                 ESGM 
                 GSM850 
               
               
                 Port 2 
               
               
                   
               
             
          
         
       
     
     As is evident from Table 2 and Table 3, traditional approaches would require the addition of ports or for diversity path  250  to support all of the wireless technologies supported by primary path  240 , thus meaning that traditional approaches may require more circuit area as compared to the methods and systems disclosed herein. 
     The advantages of the present disclosure can also be illustrated by comparing  FIGS. 2 and 3  to  FIG. 4 .  FIG. 4  illustrates a block diagram of an example terminal  400  having receiver diversity, as is known in the art. As seen in  FIG. 4 , traditional approaches employ receivers (e.g.,  220   j  and  220   k ) each dedicated to one of the primary path  240  and diversity path  250 . Accordingly, diversity path receivers cannot be reconfigured to pass signals to primary path  240 , thus providing less configuration flexibility than that provided by the present disclosure. 
     Modifications, additions, or omissions may be made to system  100 , terminal  200 , and/or terminal  300  from the scope of the disclosure. Embodiments other than those depicted in  FIGS. 1-3D  may also be utilized. The components of system  100 , terminal  200 , and/or terminal  300  may be integrated or separated. Moreover, the operations of system  100 , terminal  200 , and/or terminal  300  may be performed by more, fewer, or other components. As used in this document, “each” refers to each member of a set or each member of a subset of a set. 
     Although the present invention has been described with several embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present invention encompass such changes and modifications as fall within the scope of the appended claims.