Abstract:
Apparatus, and an associated method, for radio receiver circuitry operable in multi-modes to receive signals generated during operation of a multiple number of radio communication systems. The receiver circuitry is divided into receive chain portions which are selectably utilized depending upon which of the multiple number of the radio communication systems in which communications are to be effectuated. Selected combinations of the receive chain portions are formed, depending upon which of the modes in which the receiver circuitry is to be operable. Different combinations of the receive chain portions permit sharing of receive chain portions thereby to reduce the required number of circuit elements to form the multi-mode receiver circuitry. In one implementation, the radio receiver circuitry forms the receive portion of a dual-band, tri-mode mobile station operable in a selected one of three different cellular communication systems.

Description:
The present invention relates generally to a radio device, such as a multi-mode mobile station selectively operable in more than one mobile communication system. More particularly, the present invention relates to a multi-mode radio receiver and an associated method, in which circuitry portions required for operation of the radio receiver in its different modes of operation are shared. By sharing the circuitry portions, cost-savings and size-savings are achieved. 
     BACKGROUND OF THE INVENTION 
     Information is communicated in a communication system between two or more communications stations. Information which is to be communicated between the communication stations is transmitted upon a communication channel formed to extend between the communication stations. In a two-way communication system, a communication station includes both a transmitter and a receiver operable to transmit and to receive, respectively, communication signals. Thereby in a two-way communication system, information is both transmitted and received at a single communication station. 
     A radio communication system is a communication system in which the communication channel formed between the communication channels is a radio channel defined upon a portion of the electromagnetic spectrum. 
     A radio communication system inherently increases communication mobility as communication channels defined in such a system are formed of radio channels and do not require wireline connections to form the communication channels. A radio communication system, however, typically is bandwidth-limited. That is to say, regulatory bodies which allocate usage of the electromagnetic spectrum allocate only a limited amount of the electromagnetic spectrum for communications in a particular radio communication system. Because the spectrum allocation for use by a particular system is limited, communication capacity increase of a radio communication system is limited by such allocation. Efforts are made, therefore, to construct a radio communication system in manners which efficiently utilize the allocated spectrum. 
     A PCS, or other mobile communication system is exemplary of a radio communication system. Mobile communication systems make relatively efficient use of the spectrum allocated thereto. Signals generated during operation of the mobile communication system are of relatively low power levels. Because of the use of low-power signals, the same channels can be reused throughout a mobile communication system according to a cell reuse plan. Concurrent use of the same channels is permitted according to the cell reuse plan, thereby to effectuate concurrent communications on the same channels by different communication station pairs at different locations throughout the area encompassed by the mobile communication system. 
     However, even with the relatively efficient utilization of the allocated spectrum, many mobile communication systems have been operated at their maximum capacities, particularly at certain-times-of-day and within certain cells of the mobile communication system. With technological advancements and the need to address the capacity problems of conventional mobile communication systems, various mobile communication systems have been developed which permit increased capacities of communication therein. 
     In many instances, the mobile communication systems of such increased capacities require the installation of separate network infrastructures and the construction of separate mobile stations to be operable to communicate therewith. The separate network infrastructure are commonly overlaid upon existing mobile communication systems. And, mobile systems constructed according to different communication standards have been installed also in non-overlapping geographical areas. That is to say, different types of mobile communication systems are installed in different geographical areas. A mobile station operable pursuant in only one of the systems is operable only in the geographical area encompassed by such system. 
     Dual-mode mobile stations, for instance, are available to permit a user to communicate alternately by way of two different mobile communication systems. More generally, multi-mode mobile stations have been developed to permit their operation in multiple different mobile communication systems. Such dual- and multi-mode mobile stations typically must include circuitry specifically constructed for each of the different mobile communication systems in which the mobile station is operable. The various communication systems, for instance, are operable at different frequency bands, with different modulation schemes, with different coding schemes, etc. Therefore, conventional dual- and multi-mode mobile stations are sometimes to include separate, but functionally redundant, circuit paths for each of the communication systems in which the mobile station is to be operable. 
     Such duplication increases the complexity of the mobile station as well as the costs of the mobile station. And, because the redundant circuit paths each require separate circuit elements, the physical size of the resultant mobile station increases. 
     However, different ones of the mobile communication system standards sometimes exhibit some commonalities. For instance, the same modulation schemes are utilized but at different frequency ranges. Or, different modulation schemes might be utilized in the different communication systems but at the same range of frequencies. 
     For instance, an analog system such as AMPS (Advanced Mobile Phone System) is operable at a frequency range located about 800 MHz and utilizes an FDMA (Frequency Division Multiple Access) method. This system utilizes frequency modulation techniques to modulate information which is to be communicated during its operation. A digital systems such as PCS (Personal Communication System) which is operable at a frequency range of about 1.9 GHz utilizes various access methods, including a CDMA (code division, multiple-access). CDMA systems generally utilize QPSK (Quadrature Phase Shift Keying) modulation technique. Therefore, this same modulation technique is also utilized for CDMA systems operable at the cellular band of frequencies, i.e., the range located at about 800 MHz. 
     If advantage could be taken of the commonality of the different systems in which a multi-mode mobile station is to be operable, sharing of circuitry portions of the different circuit branches could be made. Such sharing would reduce the cost of the mobile station, along with permitting a reduction in the physical dimensions of the resultant mobile station. 
     It is in light of this background information related to radio devices, such as mobile stations operable in mobile communication systems, that the significant improvements of the present invention have evolved. 
     SUMMARY OF THE INVENTION 
     The present invention, accordingly, advantageously provides a manner by which to share circuitry portions required for operation of a multi-mode radio receiver. Circuitry portions, which conventionally form separate circuit chain portions, are shared in an embodiment of the present invention. By sharing the circuitry portions, the radio receiver is of less costly construction. And, because sharing of the circuitry portions results in a reduction of parts required of the radio receiver, a reduction in the physical dimensions required of the radio receiver is also provided. 
     In one aspect of the present invention, radio-frequency receive chain portions are used to act upon first receive signals and second receive signals generated during operation of a first mobile communication system and a second mobile communication system, respectively. The first and second mobile communication systems are operable over a common frequency band, thereby to permit the RF receive chain portion to be shared, operable to receive either the first receive signal or the second receive signal. 
     In another aspect of the present invention, a lower-frequency receive chain portion, for example, an IF (intermediate frequency) level or baseband level receive chain portion, is operable alternately to act upon indications of a first receive signal generated during operation of a first mobile communication system and a second receive signal generated during operation of a second mobile communication system. The first and second mobile communication systems are operable pursuant to a common modulation scheme, thereby to permit the lower-frequency receive chain portion to be used to act upon the indications of either the first or the second radio signals. 
     In yet another aspect of the present invention, a radio receiver of a trimode radio device is provided. The radio receiver is operable to receive and to act upon, a first radio signal generated by a first radio communication system, a second radio signal generated by a second radio communication system, and a third radio signal generated by a third mobile communication system. An RF receive chain portion is operable to act upon the radio signals generated by at least two of the radio communication systems. Thereby, a reduction in the required number of RF receive chain portions required of the tri-mode device is reduced. In analogous manner, a lower-frequency receive chain portion is selectively operable to act further upon indications of a receive signal generated by more than one of the radio communication systems. Thereby, the required number of lower-frequency, receive chain portions required of the tri-mode device is also reduced. 
     In an exemplary implementation, a dual-frequency band, tri-mode mobile station is provided. The mobile station is selectably operable in a PCS-CDMA communication system, an AMPS system, and a cellular-CDMA system. A first, RF receive chain portion is operable to act upon receive signals generated during operation of the PCS-CDMA system. The first, RF receive chain portion is operable also to down-convert such signal to an IF frequency. A second receive chain portion is operable to receive and to act upon receive signals generated during operation of the cellular-CDMA system and the AMPS system. The second RF receive chain portion is operable also to down-convert in frequency receive signals acted upon thereat to an IF frequency. Because the second RF receive chain portion acts upon signals generated during operation of two separate systems, a reduction in circuitry relative to conventional constructions of such a mobile station is achieved. The mobile station further includes a common receive chain portion coupled to both the first and second RF receive chain portions. The common receive chain portion acts upon indications of a selected one of the receive signals applied to, and acted upon, the first and second RF receive chain portions. The common receive chain portion includes a CDMA demodulator to demodulate the signals generated, alternatively, by the PCS-CDMA system and the cellular-CDMA system. Because the common receive chain portion acts upon signals generated by two separate communication systems, a reduction in circuitry is again achieved. The mobile station further includes a third receive chain portion coupled to the second RF receive chain portion, and selectably operable to act upon indications of the receive signal generated during operation of the AMPS system. 
     In yet another aspect of the present invention, biasing and switching circuitry is shared between the first and second RF receive chain portions. Because only one or the other of the RF receive chain portions is selected to be operable at a particular time period, such biasing and switching circuitry need only be coupled to the operable one of the RF receive chain portions. Additional reduction in circuitry required of the mobile station is thereby further achieved. 
     In these and other aspects, a multi-mode radio receiver, and an associated method is provided. The multi-mode radio receiver is operable to receive first receive signals generated during operation of a first radio communication system and to receive at least second receive signals generated during operation of at least a second radio communication system. A first receive chain portion has a front end side and a back end side. The front end side of the first receive chain portion is coupled to receive indications of the first receive signal. The first receive chain portion is selectably operable to act upon the indications of the first receive signal. A second receive chain portion has a front end side and a back end side. The front end side of the second receive chain portion is coupled to receive indications of the second receive signal. The second receive chain portion is selectably operable to act upon the indications of the second receive signal. Either one, but not both, of the first receive chain portion and the second receive chain portion are selected to be operable during a selected period. A common receive chain portion is coupled both to the back end side of the first receive chain and to the back end side of the second receive chain. The common receive chain acts further upon a selected one of the indications of the first receive signal and the indications of the second receive signal. The selected one corresponds to which of the first receive chain portion and the second receive chain portion is selected to be operable during the selected period. 
     A more complete appreciation of the present invention and the scope thereof can be obtained from the accompanying drawings which are briefly summarized below, the following detailed description of the presently-preferred embodiments of the present invention, and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a functional block diagram of a mobile station of an embodiment of the present invention positioned to transceive communication signals in three separate radio communication systems. 
     FIG. 2 illustrates a functional block diagram of a portion of the mobile station shown in FIG. 1 of an embodiment of the present invention. 
     FIG. 3 illustrates a method flow diagram listing the method of operation of an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1, a communication arrangement, shown generally at  10 , includes a multi-mode mobile station  12  capable of transceiving communication signals with a plurality, here three, radio communication systems. In the exemplary implementation, the mobile station  12  forms a dual-band, tri-mode, cellular mobile station selectably operable in three separate mobile communication systems. While the following description shall describe the mobile station  12  with respect to such an implementation, it should be understood that other embodiments of the present invention can analogously be implemented to be operable in other types of communication systems. 
     Three separate network infrastructures, a first network infrastructure  14 , second network infrastructure  16 , and a third network infrastructure  18  are installed and are permitting of radio communications with the mobile station  12  when the mobile station is positioned in a geographical area encompassed by the network infrastructure of the respective communication systems. The separate network infrastructures may be overlaid, or partially overlaid, upon one another. Or, the network infrastructure may be installed at separate geographical areas, and the mobile station communicates with the respective one of the separate radio communication systems when the mobile station is positioned in the geographical area encompassed by such respective communication system. 
     The network infrastructure  14  is here representative of a PCS-band, CDMA (code division, multiple-access) mobile communication system operable at approximately 1.9 GHz. The network infrastructure  16  is representative of a cellular-band, CDMA mobile communication system operable at about 800 MHz. And, the network infrastructure  18  is representative of the network infrastructure of a cellular-band, AMPS (advanced mobile phone service) mobile communication system operable also at about 800 MHz. It should be noted that the terminology of cellular and mobile shall be, at times, used interchangeably herein. 
     The network infrastructure  14 - 18  of the respective communication systems are coupled to a PSTN (public-switched, telephonic network)  22 , in conventional manner. A communication station  24  is also shown to be coupled to the PSTN. The communication station  24  is exemplary of a communication station with which communications can be effectuated with the mobile station. 
     During operation of the first cellular communication system, communication signals are transceived between the network infrastructure  14  and the mobile station. Here, first downlink communication signals  28  and first uplink signals  32  are representative of the signals communicated between the network infrastructure and the mobile station. Analogously, during operation of the second cellular communication system, communication signals are transceived between the network infrastructure  16  and the mobile station  12 . Here, second downlink communication signals  34  and second uplink communication signals  36  are representative of communication of the signals between the network infrastructure and the mobile station. And, during operation of the third cellular communication system, communication signals are transceived between the network infrastructure  18  and the mobile station  12 . Here, third downlink communication signals  38  and third uplink communication signals  42  are representative of signals communicated during operation of the third cellular communication system. 
     The mobile station  12  is here shown to include transmitter circuitry  44  and receiver circuitry  46 . Information sourced at the mobile station is acted upon by the transmitter circuitry and transduced by an antenna transducer  48  to form, selectably, the uplink communication signals,  32 ,  36 , and  42 , as appropriate. And, when any of the first, second and third downlink communication signals  28 ,  34 , and  38  are detected at the transducer  48  and converted in electrical form to be applied to the receiver circuitry  46 , the receiver circuitry is selectably operable to act upon the signals applied thereto. 
     The mobile station  12  is further shown to include control circuitry  52  operable to control operation of the transmitter and receiver circuitry  44  and  46 , respectively. The control circuitry controls operation of the respective circuitry to cause operation of the mobile station in a selected one of the different cellular communication systems with which the mobile station  12  is operable. By appropriate control over which of the communication systems with which the mobile station is operable, an available one, or a desired one, of the cellular communication systems, is caused to be utilized by the mobile station. 
     FIG. 2 illustrates the receiver circuitry  46  of an embodiment of the present invention. In the exemplary implementation, the receiver circuitry  46  forms a portion of the mobile station  12  of a dual-band, tri-mode mobile station. While the circuitry  46  of the exemplary implementation shown in the Figure is representative of the circuitry of such a device, in other implementations, the receiver circuitry is alternately configured to be operable in selected communication systems, as appropriate. 
     The receiver circuitry  46  here includes a first receive chain portion  62 , a second receive chain portion  64 , a common receive chain portion  66 , and a third receive chain portion  68 . 
     The first receive chain portion  62  includes a front end side coupled to the antenna transducer  48  (shown in FIG.  1 ), thereby to receive indications of the first downlink communication signal  28  (shown in FIG.  1 ), when detected at the mobile station of which the receiver circuitry forms a portion. The indications are applied to the portion  62  on the line  69 , here indicated as “PCS RF In.” Analogously, the second receive chain portion  64  also includes a front end side, also coupled to the antenna transducer (shown in FIG.  1 ), thereby to receive indications of the second downlink communication signal  34  (shown in FIG.  1 ). The indications are applied to the portion  64  on the line  71 , here indicated as “CELLULAR RF In.” The first and second receive chain portions  62  and  64  further define back end sides to which the common receive chain portion  66  is coupled. The first and second receive chain portions are coupled to the common receive chain portion in a wired-OR configuration in which indications of either the first receive signal, once acted upon by the first receive chain portion, or indications of the second receive chain portion once acted upon by the second receive chain portion are provided to the common receive chain portion to be acted further upon thereat. 
     The third receive chain portion  68  is also coupled to the back end side of the second receive chain portion  64  and is selectably operable, alternate to operation of the common receive chain portion. 
     The first receive chain portion  62  forms an RF (radio frequency)-stage of a PCS-band receive operable at about 1.9 GHz. Indications of the first receive signal, detected at the antenna transducer  48  and converted into electrical form thereat, are provided to a low-noise amplifier (LNA)  72 . The LNA  72  is a switched amplifier which permits bypassing of the amplifier if determinations are made that amplification at the LNA is unnecessary. Such switching is performed by a switch element  74 . Selection of the switch position of the switch element  74  is made by biasing and switching circuitry  75  to position the switch element  74  in a desired switch position. The LNA  72  is coupled to a PCS-band filter  76  which has a passband to pass signal frequency within the PCS passband. Signal frequencies passed by the filter  76  are applied to an RF amplifier  78  to be amplified thereat. The amplifier  78  is biased by shared biasing circuitry  80 . Once amplified, the signal is provided to a first input of a mixer  82 . A down mixing signal, the “LO In” signal, generated on the line  84  is applied to a second input of the mixer  82  by way of an isolating buffer  85 . The buffer  85  is biased by shared biasing circuitry  86 . The mixer operates as a down-mixer to down-convert in frequency the amplified signal applied to the first input of the mixer to form an IF (intermediate frequency)-frequency signal on the line  87  extending from an output of the mixer. The IF signal is applied to an IF-stage amplifier  88 , here a differential amplifier. The amplifier is biased by shared biasing circuitry  90 . Differential, amplified signals are generated on the lines  92 , and the lines  92  are connected to the common receive chain portion  66 . 
     The second receive chain portion  64  forms an RF-stage of a cellular-band receiver operable at cellular frequencies of about 800 MHz. Indications of the second downlink signals detected at the antenna transducer  48  and converted into electrical form thereat are applied to an input of a low-noise amplifier (LNA)  102 . The LNA  102  is a switched amplifier which permits bypassing of the amplifier if determinations are made that amplification at the LNA is unnecessary. Such switching is performed by a switch element  104 . Selection of the switch position of the switch element  104  is made by the shared biasing and switching circuitry  75 . The LNA  102  is coupled to a cellular band filter  106  having a passband to pass signal frequencies within a cellular band of approximately 800 MHz. Signal frequencies passed by the filter  106  are amplified by an RF amplifier  108 . The amplifier  108  is biased by biasing circuitry  80 . Amplified signals are applied to a first input of a mixer  112 . A down-mixing signal, the “LO In” signal, generated on the line  114  is applied to a second input of the mixer  112  by way of an isolating buffer  115 . The buffer  115  is biased by shared biasing circuitry  86 . The mixer  112  is operable to down-convert the indications of the second receive signal applied to the first input of the mixer in frequency to an IF frequency. An IF signal is formed on the line  116  at an output of the mixer  112 . The line  116  is coupled to an input of a differential amplifier  118  operable to generate amplified signals on the line  92 . The amplifier is biased by the shared biasing circuitry  90 . The lines  92  are connected to the common receive chain portion  66 . 
     The line  116  is also coupled to an input of an amplifier  122 . The amplifier  122 , an output line of which is coupled to the third receive chain portion  68 . The amplifier is selectably operable to amplify the IF signal formed on the line  116  and to apply such signal, once amplified, to an IF filter  124 . Signal frequencies within the passband of the filter  124  are applied to a receiver backend FM Demodulation element  126 . The element  126  performs functions such as baseband down conversion and demodulation operations. The FM demodulation can be performed by digital or analog methods. 
     The lines  92 , connected to the differential outputs of the IF amplifiers  88  and  118  of the first and second receive chain portions  62  and  64 , respectively, are coupled to an IF filter  144  which forms a portion of the common receive chain portion  66 . The filter  144  exhibits a passband corresponding to the passband to pass signal frequencies of CDMA signals generated during operation of a cellular, CDMA system, either of those operable at a PCS-band frequency or operable at a cellular-band frequency. Signal frequencies passed by the filter  144  are applied to a receiver backend I/Q Demodulation element  146 . The element  146  performs functions such as baseband down conversion and demodulation operations. 
     The receiver circuitry  46  shown in the Figure is of reduced circuit element count relative to conventional such constructions because circuit paths are shared amongst the circuit paths required for operation of the different mode of which the mobile station is operable. Advantage is taken of the fact that the mobile station is operable in a single mode at a time. That is to say, when the mobile station is operable to communicate pursuant to the first communication network, here a PCS-band, CDMA system, only the circuit path relating to that communication system is operable. In one implementation, the IF-stage amplifiers  88 ,  118 , and  122 , are selectably powered. Such selective powering of the amplifiers is determinative of operation of the receiver circuitry. 
     When the mobile station of which the receiver circuitry forms a portion is to be operable in a PCS-band, CDMA mode, the IF-stage amplifier  88  is powered while the amplifiers  118  and  122  are not powered. Thereby, a receive chain, formed of the receive chain portion  62  and the common receive chain portion  66  acts upon signals received at the mobile station. When, conversely, the mobile station is to be operable in the cellular-band, CDMA mode, the amplifier  118  is caused to be powered while the amplifiers  88  and  122  are caused not to be powered. Thereby, the second receive chain portion  64  and the common receive chain portion  66  form a receive chain which acts upon the signals received at the mobile station. And when the mobile station is to be operated in a cellular-band, AMPS mode, the amplifier  122  is caused to be powered, and the amplifiers  88  and  118  are caused not to be powered. Thereby, the second receive chain portion  64  and the third receive chain portion  68  form a receive chain for acting upon signals received at the mobile station. In other implementations, other manners are used by which to selectably connect the different portions  62 ,  64 ,  66 , and  68  to form a receive chain, operable as desired. In similar manner, the shared circuitry  75 ,  80 ,  86 , and  90  is operable with a selected one of the first receive chain portion with a second receive chain portion. Circuit element-count is thereby reduced, relative to conventional constructions of the receiver circuitry  48 . 
     FIG. 3 illustrates a method, shown generally at  172 , of an embodiment of the present invention. The method selectably acts upon a first receive signal and at least a second receive signal when received at a multimode radio receiver operable to receive first receive signals generated during operation of a first radio communication system and to receive at least second receive signals generated during operation of at least a second radio communication system. 
     First, and as indicated by the block  174 , indications of the first receive signal, if received at the multi-mode receiver, are applied to a first receive chain portion. And, indications of the second receive signal, if received at the multi-mode receiver, are applied to a second receive chain portion. 
     Then, and as indicated by the block  176 , the indications of the first receive signal are selectably acted upon at the first receive chain portion, and the indications of the second receive signal are selectably acted upon at the second receive chain portion. Either one, but not both, of the first receive chain portion and the second receive chain portion are operable during the selected period. 
     Then, and as indicated by the block  178 , indications of a selected one of the indications of the receive signal and the indication of the second receive signal are applied to a common receive chain portion. And, as indicated by the block  182 , the indications of the selected one of the indications of the first and second receive signal, applied to the common receive chain portion are further acted upon. 
     The previous descriptions are of preferred examples for implementing the invention, and the scope of the invention should not necessarily be limited by this description. The scope of the present invention is defined by the following claims.