Abstract:
A product and system is disclosed for intelligently controlling the number of amplifier modules that are active in a linear amplification system. By exercising such control, the system can avoid using unnecessary power. The invention monitors the system and gathers information from signals associated with the system, particularly information concerning signal power. A control functionality evaluates the gathered information to decide how many modules are necessary to sufficiently operate the amplification system or to decide if it has been commanded to perform certain functions. Once this decision is made, the control functionality communicates control signals to the power amplification modules to activate the needed or desired number of modules and deactivate the unneeded or undesired number of modules. Likewise, the control functionality configures the splitter and the combiner according to the number of needed or desired amplifier modules. This gathering, evaluation, and control is conducted continuously.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates in general to the field of wireless telecommunications and in particular to the field of power conservation in the amplification of communication signals.  
         BACKGROUND OF THE INVENTION  
         [0002]    Systems comprising multiple linear power amplifiers have many applications. For example, multiple-channel, four-module linear amplifier systems are used in cellular-telephone base stations or “cell sites”. Such base stations, or cell sites, are well known and are described, for instance, in George Calhoun,  Wireless Access and the Local Telephone Network  128-135 (1992), which is incorporated herein by reference. Such amplifier systems are used within cell sites to amplify multiple radio-frequency (RF) signals of various and differing frequencies, or channels or carriers. Such a system typically comprises a splitter, a plurality of linear amplifier modules, a combiner, a splitter/combiner control functionality, and a monitor and control module. Examples of such a system include the Spectrian MC160A series of multi-carrier power amplifiers and the PowerWave MCA9000-400 series of linear amplification systems.  
           [0003]    In such a system, an “input signal” is fed into a splitter. This input signal comprises one or more radio-frequency signals of differing frequencies. In other words, this input signal may be a multiple-channel signal. These radio-frequency signals may be in any desired format or protocol, including Advanced Mobile Phone Service (AMPS), Time Division Multiple Access (TDMA), or Code Division Multiple Access (CDMA) standards. The splitter splits the input signal into two or more resulting signals. The resulting signals contain the same frequencies as the input signal, but the power, or amplitude, of the input signal is equally divided among the resulting signals. The splitter in a typical four-module linear amplifier system, such as the PowerWave MCA9000-400 Series Four Module Linear Amplification System, features four outputs, each of which are coupled to one of four linear amplifier modules. The splitter is configured according to the number of linear amplifier modules that are coupled to the splitter and operational. A splitter/combiner control functionality, embodied by, for example, a microprocessor or shelf logic, monitors the number of amplifier modules that are coupled to the splitter and operational, and configures the splitter and combiner accordingly. In a four-module system in which all four modules are operational, the splitter/combiner control functionality configures the splitter for four modules such that the splitter splits an input signal into four resulting signals, each of which comprise the same frequency content as the input signal and are one-quarter the power. When the splitter is configured according to three coupled and operational amplifier modules, the splitter splits the input signal into three resulting signals, each of equal power, one-third of the input signal. Similarly, when the splitter is configured for two modules, the splitter splits the input signal into two signals, and when the splitter is configured for one module, the splitter does not split the signal.  
           [0004]    Each of the four modules amplifies the signal input to that module to a desired level. The amplified signals are coupled to a combiner. The splitter/combiner control functionality configures the combiner according to the number of power modules coupled to the splitter and that are operational. Thus, in a four-module system, the splitter/combiner control functionality logic configures the combiner for operation in such a system. Accordingly, the combiner combines the four amplified signals into a single output signal for transmission. Typically, this combined output is fed through antenna interface circuitry to a transmit antenna.  
           [0005]    Also in such a system, a monitoring and control device is employed to provide and control operating power to each of the modules, to monitor each of the modules, to activate or deactivate all of the modules, and to notify the operator if the system is operating outside of parameters. This device may also be used to configure and reconfigure the splitter and combiner, together with or in place of the splitter/combiner control functionality.  
           [0006]    In the systems used in conventional cellular-telephone cell sites, the monitoring and control device does not activate or deactivate individual power amplifier modules independently. All of the modules are either active or all of the modules are inactive.  
           [0007]    The multiple-channel, multiple-amplifier linear amplifier systems employed in conventional cell-sites require considerable power and are consequently expensive to operate. A power supply at a conventional cell-site typically provides power to the system at 24-27 DC Volts and the current needed by the system at the time. The power needed by the system typically varies over time each day according to subscriber use of the system. During peak hours, when subscriber demand is highest, the system may require 1500-2500 Watts. During off-peak hours, the power requirement of the system may be approximately 150 Watts, drastically less than the peak-hours demand.  
           [0008]    A large part of the power required to operate a four-module linear amplifier system can be thought of in some respects as overhead—it simply maintains all four of the power amplifier modules in an active state when the system is in operation. During peak hours, all four power amplifiers are often needed to amplify the signals handled by the system. Thus, it is often necessary to maintain all four power-amplifiers in the active state during peak hours. During off-peak hours, however, the system may need only one or two of the power amplifiers modules for sufficient operation. It may thus be that only one or perhaps two of the amplifier modules are required to be active during off-peak hours. Maintaining only the required amplifier modules in the active state would require considerably less overhead power.  
           [0009]    As mentioned above, the conventional systems do not provide for control over the activation or deactivation of individual power amplifier modules. Rather, all modules remain in the same operation state at any particular time. For example, in a conventional four-module system, all four modules remain in the active state during both peak and non-peak hours. Thus, because all of the modules are either active or inactive at all times, the power amplifier modules use more power than is necessary for sufficient operation of the system. Conventional systems accordingly use power inefficiently and are therefore more expensive to operate than necessary.  
         SUMMARY OF THE INVENTION  
         [0010]    Linear power amplifier systems accordingly to the present invention include an input line, a splitter, a plurality of linear power amplifier modules, a combiner, and a control functionality. The control functionality configures the splitter and combiner according to the number of active amplifier modules coupled to the splitter. The input line delivers a number of input signals on a number of channels to the splitter, which splits the signals among a number of splitter outputs according to its configuration. Each splitter output is coupled to a linear power amplifier module. The signals allocated to each splitter output are communicated by this connection to the corresponding amplifier module. Each linear amplifier module amplifies the communicated signals, and the output of each module is provided to a combiner. The combiner combines the amplified signals according to its configuration and outputs the combined signal, eventually to a radiator. The control functionality, which may be implemented in a microprocessor, receives signals from the system, evaluates them, and uses them to control the linear power amplifier modules. The control functionality evaluates, among other things, how many linear amplifier modules should be in the active state and how many should be in the inactive state at any particular point in time. This decision may be based upon how many amplifier modules are necessary to carry out the system&#39;s objectives. The control functionality will examine the signals it receives from the system to determine, among other things, the volume of signals the system is currently handling. The control functionality may determine the volume of signals the system is currently handling by evaluating the power level of the signals. The control functionality is programmed to determine how many amplifier modules are needed by the system to amplify the detected volume of signals. In addition, this decision may be based, in part or in whole, upon human intervention, upstream information, and other factors supplied by a common-control module.  
           [0011]    Linear power amplifier systems according to the present invention use power more efficiently than conventional systems. Such efficiency allows the operating cost of linear power amplification systems according to the present invention to be lower than the operating cost of conventional systems.  
           [0012]    Structural differences between systems according to the present invention and conventional systems include the communications lines facilitating independent control over individual power amplification modules. Structural differences also include the combination of structure embodying a splitter, a combiner, and individually-controlled power amplification modules in a mobile communications cell site.  
           [0013]    Systems according to the present invention employ the intelligent control of linear amplifier modules in order to increase power-use efficiency. This intelligent control is made after evaluation of states at one or points within and, if desired, without the system. These states may be a wide variety of types of signals, including CDMA, TDMA, and AMPS. Systems according to the present invention are able to evaluate these one or more types of signals and intelligently control individual amplifier modules according to that evaluation. These systems employ structures which split and combine RF signals.  
           [0014]    It is accordingly an object of the present invention to provide a linear power amplifier system that uses power more efficiently than the conventional systems by, among other things, controlling activation/deactivation of individual power amplifiers in a manner that reflects actual required capacity.  
           [0015]    It is another object of the present invention to provide a linear power system that intelligently controls multiple power amplifier modules of the system so that individual modules can be placed in the active or inactive state as desired, independent of the state of other modules.  
           [0016]    It is a further object of the present invention to provide a mobile communications linear power amplifier that requires less power to operate than conventional mobile communications power amplifiers.  
           [0017]    Other objects, features, and advantages of the present invention will be apparent with respect to the remainder of this document. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 schematically shows an embodiment of linear power amplifier systems of the present invention with four power-amplifier modules, a control functionality monitoring the system output, a single communications line between the control functionality and the modules, and a splitter/combiner control functionality monitoring the modules and accordingly configuring the splitter and the combiner.  
         [0019]    [0019]FIG. 2 schematically shows a second embodiment of systems of the present invention with four power-amplifier modules, a control functionality monitoring the system output and the modules, as well as configuring the splitter and combiner, and multiple communications lines between the microprocessor and the modules.  
         [0020]    [0020]FIG. 3 schematically shows a third embodiment of systems of the present invention with four power-amplifier modules, a control functionality monitoring both the system output and the system input, as well as configuring the splitter and combiner accordingly, and a single communications line between the microprocessor and the modules.  
         [0021]    [0021]FIG. 4 schematically shows a fourth embodiment of systems of the present invention with four power-amplifier-modules, a control functionality monitoring the output of a common-control module, and a single communications line between the microprocessor and the modules, in which the common-control module is monitoring the communications bus of the site transmitters and is configuring the splitter and combiner.  
         [0022]    [0022]FIG. 5 schematically shows a fifth embodiment of systems of the present invention with four power-amplifier-modules, a microprocessor monitoring the output of a common-control module, and a single communications line between the microprocessor and the modules, in which the common-control module is monitoring the communications directed to the common-control module by the central operations site through a site receiver and is configuring the splitter and the combiner.  
         [0023]    [0023]FIG. 6 schematically shows a subscriber station, including a linear amplification system, according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]    The present invention provides intelligent control of multiple linear power amplifier modules. The control functionality, which may be implemented in a microprocessor, logic circuitry, or in distributed processing, using artificially intelligent or rules-based implementations, neural net, or any other desired mode or control process, monitors the system and other factors if desired, and provides control to the amplification capacity of the system based on its monitoring and evaluation. By activating only the amplifier capacity necessary for sufficient operation of the system, this intelligent control functionality provides a linear power amplifier system that uses power in a more efficient manner than conventional systems.  
         [0025]    According to the preferred embodiment, a multiple-channel, four-module linear amplifier system is of the sort used in cellular-telephone cell sites. The present invention, however, can be embodied in various other systems, including PCS sites, other mobile radio sites, systems with more or less than four modules, and systems used at locations other than mobile radio sites.  
         [0026]    In a preferred embodiment, the control functionality is coupled to one or more circuits or components (“points”) within and, if desired, without the system, in order to monitor various states inside (and, if desired, outside) the system, such as input or output at various points in the system. The control functionality evaluates the state at such point(s) in order to determine how many of the power amplification modules are needed to meet the demand on the system at that time. Point(s) to which the control functionality may be coupled include points in system input, system output, output of a common control module, points external to the system, or a combination thereof. States which may be monitored in the system preferably include signal power at those points. After determining how many modules are necessary for sufficient operation of the system, the control functionality activates the particular modules needed at that particular time and deactivates the modules not needed at that time. As in conventional systems, a control functionality, such as implemented in a microprocessor or other logic circuits, monitors the modules. The control functionality configures the splitter and the combiner according to the number of modules that are present and operational.  
         [0027]    The control algorithm for the splitter and combiner carried out by the control functionality or the splitter/combiner control functionality according to the present invention needs to be such that dynamic reconfiguration of the splitter and combiner, and dynamic activation and deactivation of amplifier modules, are controlled to maintain gain in the system. Particularly if the splitter and dynamic activation and deactivation of amplifier modules are not carefully controlled, the modules may become overloaded and damaged.  
         [0028]    Some conventional splitters and combiners have control inputs that may be used in accordance with the present invention to dynamically reconfigure the splitter and combiner according to the number of amplifier modules in the active state. Other splitters and combiners will require a new control interface, one that is capable of coupling to a control functionality or a splitter/combiner control functionality according to the present invention.  
         [0029]    The design, construction, and operation of systems according to the present invention is flexible depending upon the needs of the application to which the invention is directed. The number and location of points within the system to which the control functionality is coupled may be varied. The control functionality is responsive to certain states or ranges of states at the points to which the control functionality is coupled. Human intervention, external control intervention, or other external input can be employed to override or modify the manner in which the modules are activated regardless of states in the system that reflect certain capacity requirements. The control functionality, whether or not distributed, can also be implemented to evaluate and adjust the operation-state of the modules at preselected time intervals, at random time intervals, or, preferably, continuously.  
         [0030]    [0030]FIG. 1 shows a four-module linear amplifier system  10  embodying the present invention according to the best mode. The system  10  includes a splitter  16 , four power amplifier modules  28 ,  29 ,  30 ,  31 , a combiner  54 , and a control functionality  62 . When the system is in operation, one or more radio-frequency signals (not shown) in a format such as AMPS, TDMA, or CDMA are provided on an input line  14  to the splitter input  18  into the splitter  16 . The splitter  16  allocates the signals among multiple splitter outputs  20 ,  21 ,  22 ,  23  according to the volume of inputted signals, the signals&#39; degradation, which amplifier modules are in the active state, and other factors.  
         [0031]    The splitter in the system shown in FIG. 1 has four outputs  20 ,  21 ,  22 ,  23 . These outputs  20 ,  21 ,  22 ,  23  are coupled to four linear amplifier modules  28 ,  29 ,  30 ,  31 .  
         [0032]    Each linear amplifier module has at least two operation states, the active, or amplifying or “on,” state and the inactive, or open or “off,” state. An amplifier module that is in the active state amplifies the inputted signal at a preselected gain. Preferably, an amplifier module that is in the inactive state essentially acts as an open circuit and does not communicate a signal.  
         [0033]    Each module has a control port. The operation state of a module depends upon the signal received by that module&#39;s control port  68 ,  69 ,  70 ,  71 . If a signal preselected to cause a module to be in the active state is provided to the module&#39;s control port, the module will change to the active state if it is in the inactive state, and will remain in the active state if it is already in the active state. If a signal preselected to cause a module to be in the inactive state is provided to the module&#39;s control port, the module will change to the inactive state if it is in the active state, and will remain in the inactive state if it is already in the inactive state. The system and modules can be designed and programmed to react in a desired manner to a wide variety of signals.  
         [0034]    Each module that is in the active state amplifies the signal inputted into that module and provides an amplified signal at its output. The modules&#39; outputs are shown in FIG. 1 as  42 ,  43 ,  44 , and  45 . The outputs  42 ,  43 ,  44 ,  45  are coupled to the combiner inputs  300 ,  301 ,  302 ,  303 . The amplified signals are fed from the outputs into a combiner  54 . The combiner  54  combines the inputted signals and provides an output signal at the combiner output  56 . The combiner output  56  is the system output in the embodiment shown. The combiner output  56  may be coupled to antenna circuitry (not shown), which prepares the signal for antenna transmission.  
         [0035]    The control functionality is preferably preprogrammed. The control functionality may monitor a state such as the combiner&#39;s output signal, including particularly the power level of the output signal, to determine how many active amplifier modules are needed for the system to operate sufficiently. In that case, the combiner output  56  is coupled to the input  64  of the control functionality  62 . The control functionality evaluates the signal on its input  64  and communicates a control signal on its control output  66  to the amplifier modules  28 ,  29 ,  30 ,  31 . The control signal communicated by the control functionality  62  depends upon the signal seen by the control functionality  62  at its input. The control functionality  62  may be preprogrammed to evaluate the signal(s) on its input  64  in order to determine how many of the four power amplifier modules  28 ,  29 ,  30 ,  31  should be in the active state to operate the linear power amplifier system  10  sufficiently. For example, the control functionality may be programmed to determine that if a given level of signal power is present at the system output, the system is probably handling a certain number of calls, and only two of the power modules are necessary to amplify signals for that number of calls.  
         [0036]    If the control functionality  62 , upon evaluating the signal on its input  64 , determines that only two of the four amplifier modules  28 ,  29 ,  30 ,  31  are needed in the active state to operate the linear power amplifier system  10  sufficiently, then the control functionality  62  communicates a preselected signal to the amplifier modules&#39;s control-ports  68 ,  69 ,  70 ,  71  that causes two modules  28 ,  29  to be in the active state and two modules  30 ,  31  to be in the inactive state. This signal may be comprised of analog or digital signals as selected during design. Preferably, the signal is a digital signal. If the control functionality  62  determines that only one amplifier module is needed in the active state, the control functionality communicates a different preselected signal to the modules that causes one module to be in the active state and three modules in the inactive state. Similarly, if the control functionality determines that three amplifier modules are needed in the active state, the control functionality communicates an appropriate, predetermined signal to the modules; and if the control functionality determines that four modules are needed in the active state, the control functionality communicates an appropriate, predetermined signal to the module.  
         [0037]    The splitter/combiner control functionality  400  is coupled to the amplifier modules  28 ,  29 ,  30 ,  31 . Each amplifier module  28 ,  29 ,  30 ,  31  has an amplifier-module state output  420 ,  421 ,  422 ,  423 , which reflects the operation state of the corresponding module. The functionality  400  is also coupled to the splitter  16  and the combiner  54 . The functionality&#39;s coupling to the amplifier modules  28 ,  29 ,  30 ,  31  allows the functionality  400  to monitor the modules&#39; operation-state and determine how many and which of the amplifier modules are in the active state. The functionality uses this information to configure the splitter  16  and combiner  54  accordingly. Thus, if the control functionality  62  determines that only two amplifier modules are necessary for sufficient operation of the system, and activates two amplifier modules and deactivates two modules, the splitter/combiner control functionality  400  will recognize that only two modules are in the active state, and configure the splitter and the combiner accordingly. Thus, if only two amplifier modules  28 ,  29 , are in the active state, the splitter/combiner control functionality  400  will configure the splitter such that the splitter splits the input signal into two signals that are communicated to only two splitter outputs  20 ,  21 . Likewise, the functionality  400  will configure the combiner such that the combiner combines signals on only two of its combiner inputs  300 ,  301 . The system according to FIG. 1 is an improvement over the contentional systems because it provides dynamic independent control over individual amplifier modules as desired.  
         [0038]    [0038]FIG. 2 shows another embodiment of the present invention. The system of FIG. 2 operates in essentially the same manner as the system of FIG. 1, described above. The control functionality of the system shown in FIG. 2, however, is constructed, and operates, differently than the control functionality described above. The control functionality shown in FIG. 2 has four control outputs  100 ,  101 ,  102 ,  103 , and each control output is coupled to one, and only one, amplifier-control port,  68 ,  69 ,  70 ,  71 . Also, the function of the splitter/combiner control functionality  400  in FIG. 1 is carried out by the control functionality  62  of FIG. 2.  
         [0039]    If the control functionality  62 , upon evaluating the signal on its input  64 , determines that only two of the four amplifier modules  28 ,  29 ,  30 ,  31  are needed in the active state to sufficiently operate the linear power amplifier system  10 , then the control functionality  62  provides a digital 1 on two of its control outputs  100 ,  101 , and a digital 0 on the other two  102 ,  103 . Accordingly, a digital 1 is communicated to two amplifier-control ports  68 ,  69 , and a digital 0 is communicated to the other two amplifier-control ports  70 ,  71 . Each amplifier module is programmed to be in the active state when a digital 1 is on its amplifier-control port and to be in the inactive state when a digital 0 is on its amplifier-control port. Thus, when the control functionality  62  communicates two digital 1s and two digital 0s, two of the modules  28 ,  29  are in the active state and two of the modules  30 ,  31  are in the inactive state.  
         [0040]    If the control functionality  62  determines that only one amplifier module is needed in the active state, the control functionality communicates one digital 1 and three digital 0s, and thus one of the modules  28  is in the active state, and the other three modules  29 ,  30 ,  31  are in the inactive state. Similarly, if the control functionality determines that three amplifier modules are needed in the active state, the control functionality communicates three digital 1s and one digital 0, and thus three of the modules  28 ,  29 ,  30  are in the active state, and the other module  31  is in the inactive state. If the control functionality determines that four modules are needed in the active state, the control functionality communicates four digital 1s and no digital 0s, and accordingly all four modules  28 ,  29 ,  30 ,  31  are in the active state.  
         [0041]    In FIG. 2, the control functionality  62  is coupled to the splitter  16  and the combiner  54 . Also, the control functionality  62  is coupled to the four amplifier modules  28 ,  29 ,  30 ,  31 . While performing the determinations described in the preceding paragraph, if the control functionality  62  determines that three amplifier modules are needed in the active state, the control functionality, in addition to communicating to the amplifier modules, configures the splitter  16  and the combiner  54  for operation with three amplifier modules. In such a configuration, the splitter will split the input signal into three signals at the splitter outputs  20 ,  21 ,  22 , and the combiner will combine signals on three of the combiner inputs  300 ,  301 ,  302 . Likewise, if the control functionality  62  determines that only one amplifier module is needed, the functionality  62  configures the splitter  16  and combiner  54  for operation with one amplifier module.  
         [0042]    [0042]FIG. 3 shows another embodiment of the present invention. The system shown in FIG. 3 operates essentially the same as the system shown in FIG. 1. However, the control functionality  62  shown in FIG. 3 has two control functionality inputs  64 ,  65 . One of the control functionality inputs  64  is coupled to the combiner output  56  just as the single control functionality input is coupled to the combiner output in FIG. 1 and FIG. 2. The second control functionality input  65  of the system shown in FIG. 3 is coupled to the input line  14 . Accordingly, the system input signal is communicated not only to the splitter input  18 , but is also communicated to one of the control functionality inputs  65 . Preferably, the control functionality  62  is preprogrammed with the gain of the system. The control functionality can also be preprogrammed to calculate the system gain from its input(s) and if connected appropriately, preferably as shown in FIG. 3. The control functionality  62  shown in FIG. 3 uses both the system output signal and the system input signal to determine how many amplifier modules should be in the active state and how many should be in the inactive state to provide the amplification necessary for satisfactory system operation. As discussed above, after making such an evaluation, the control functionality sends control signals to the modules to activate the necessary modules and deactivate the unnecessary modules.  
         [0043]    Moreover, the configuration of the splitter  16  and the combiner  54  shown in FIG. 3 is controlled by the control functionality  62 . In the embodiment shown in FIG. 3, however, the functionality  62  is not coupled to the amplifier modules  28 ,  29 ,  30 ,  31 . The modules  28 ,  29 ,  30 ,  31  are not monitored by the functionality  62  in the functionality&#39;s determination of how the splitter  16  and combiner  54  should be configured (the functionality  62  may monitor the modules for other reasons, though (not shown)). The control functionality configures the splitter  16  and combiner  54  after determining how many modules should be activated for sufficient operation of the system.  
         [0044]    The figures herein show the preferred placement of connections to the control functionality inputs. These connections may be made anywhere within the system, however. For example, the control functionality inputs could be made to the four splitter outputs and all four amplifier outputs of the system shown in FIG. 3. This would provide essentially the same information to the control functionality as connecting the control functionality inputs to the system input line  14  and the combiner output  56  as shown in FIG. 3. The four connections to the splitter output would provide essentially the same information as the connection to the input line  14 , and the four connections to the amplifier module outputs would provide essentially the same information as the connection to the combiner output  56 .  
         [0045]    [0045]FIG. 4 shows another embodiment of the present invention. The system shown in FIG. 4 operates essentially the same as the system shown in FIG. 1. However, the system shown in FIG. 4  includes a common-control module  80 . The common control module  80  is used to monitor and control individual parts of the system as desired. It can also be used to command the control functionality to function as desired. In FIG. 4, the common-control module  80  includes two common-control inputs  83 ,  85 . One of the inputs  83  is coupled to the splitter monitor-port  91 . The splitter monitor-port  91  provides information in the form of one or more signals about the current and/or past operation of the splitter  16 . The coupling of the input  83  and the splitter monitor-port  91  allows the common-control module  80  to monitor the operation of the splitter  16 . The second input  85  is coupled to the combiner monitor-port  93 , which provides information about the current and/or past operation of the combiner  54 . The coupling between the combiner monitor-port  93  and the second input  85  allows the common-control module  80  to monitor the operation of the combiner  54 . The common-control module may also monitor individual lines, such as the input line  14  (this is not shown).  
         [0046]    The common-control module  80  shown in FIG. 4 includes two common-control outputs  82 ,  84 . One output  82  is coupled to a splitter control-port  90 . The other output  84  is coupled to a combiner control-port  91 . The splitter control-port  90  allows an outside device to control various aspects of the splitter&#39;s operation, and the combiner control-port  91  allows an outside device to control various aspects of the combiner&#39;s operation.  
         [0047]    Modern cell sites may have multiple transmitters  200 ,  201 ,  202 ,  203  that are in communication with a central operations site  210 . Central operations sites, or network controllers, are used in cellular communication. The function and structure of central operations sites, or network controllers, and their use in wireless systems are described in George Calhoun,  Wireless Access and the Local Telephone Network  129-135 (1992), which is incorporated herein by reference. The central operations site  210  monitors various cell sites and manages the cell sites&#39; operation. It may include several transmitters and receivers used in radio-frequency communication, as well as computer hardware used in monitoring and evaluating the operation of cell sites and related information, as well as communicating appropriately with cell sites.  
         [0048]    Four transmitters  200 ,  201 ,  202 ,  203  are shown in FIG. 4. These transmitters are located at the cell site along with the system structure described above. The desired frequency of operation and state for the transmitters  200 ,  201 ,  202 ,  203  are communicated to the transmitters by the central operations site  210 . For example, the central operations site  210  may communicate that the transmitters should operate at a particular frequency and that only two of the four transmitters should be in operation (or “on” ). This is accomplished by the central operations site  210  communicating using radio-frequency signals  212  with a receiver  202  placed at the cell site. The receiver  202  in turn communicates with the transmitters using a communications bus  96 . The receiver  202  transmits signals via the communications bus  96  to the transmitters  200 ,  201 ,  202 ,  203  to cause the transmitters to use the desired frequency and/or enter the desired state.  
         [0049]    The common-control module  80  includes a common-control input  81 . The common-control input  81  is coupled to the communications bus  96 . Thus, the signals on the communications bus  96  are communicated to the common-control module  80  as well as the transmitters  200 ,  201 ,  202 ,  203 . Accordingly, the common-control module  80  can monitor the communications between the receiver  202  and the transmitters  200 ,  201 ,  202 ,  203 . This monitoring allows the common-control to determine how many of the transmitters are in operation and their transmission frequency. This information is evaluated by the common-control module  80 . The common-control module  80  transmits a corresponding signal to its common-control output  86 , which is coupled to the control functionality input  64 . This corresponding signal is used by the control functionality  62  to determine how many amplifier modules should be in the active state and how many should be in the inactive state to provide necessary amplification. As discussed above, after making such an evaluation, the control functionality send control signals to the modules to activate the necessary modules and deactivate the unnecessary modules.  
         [0050]    The common-control module  80  shown in FIG. 4 carries out the monitoring and splitter/combiner configuration function of the splitter/combiner control functionality  400  of FIG. 1. The common-control module  80  is coupled to the amplifier modules  28 ,  29 ,  30 ,  31 , and thereby monitors which of the modules  28 ,  29 ,  30 ,  31  are active and which are inactive. Like the functionality  400  of FIG. 1, the common-control module  80  configures the combiner  16  and splitter  54  according to the number of amplifier modules in operation. The configuration is communicated to the splitter by the module&#39;s  80  coupling to the splitter  82 ,  90 . Likewise, the configuration is communicated to the combiner by the module&#39;s  80  coupling to the combiner  84 ,  91 .  
         [0051]    The embodiment shown in FIG. 4 can be used with conventional central operations sites. The embodiment would require no further programming of communications system at the central operation site.  
         [0052]    [0052]FIG. 5 shows another embodiment of the present invention. The system shown in FIG. 5 operates essentially the same as the system shown in FIG. 1 and FIG. 4. However, instead of monitoring the communications bus as the system shown in FIG. 4., the system shown in FIG. 5 is in direct communication with the central operations site  210 . The central operations site  210  communicates using radio-frequency signals  213  with a receiver  203  at the cell site. The receiver  203  receives these signals and transmits corresponding signals to the common-control input  81 . Thus, the central operations site  210  can send information to the common-control module  80 . This information is used by the common-control module, and in turn by the control functionality  62 , to determine how many amplifier modules  28 ,  29 ,  30 ,  31  should be in the active state and how many should be in the inactive state. The central operations site  210 , common-control module  80 , and control functionality  62  are pre-programmed such that the central operations site  210  can direct the operation state of the amplifier modules by communicating with the receiver  203  through radio-frequency signals  213 , and in turn with the common-control module  80  and control functionality  62 . The common-control module  80  shown in FIG. 5 carries out the monitoring and splitter/combiner configuration function just as the common-control module  80  shown in FIG. 4, described above.  
         [0053]    Use of the embodiment shown in FIG. 5 in conventional cellular systems would require some programming at the central operations site. The central operations site would need to be adjusted to communicate with the common-control module.  
         [0054]    Although the present invention is discussed herein in context of cellular-telephone cell sites, the present invention can be used in other settings besides cell sites. For example, it can be used in Special Mobile Radio applications. The present invention can be used in any system that uses multiple channels and conducts amplification using multiple amplifying modules.  
         [0055]    Radio base stations are well known in the art. Such stations and their operation, including their components&#39; operation, are described generally in George Calhoun,  Wireless Access and the Local Telephone Network  126-135, 241-377 (1992), which is incorporated herein by reference. FIG. 6 schematically shows an embodiment of a subscriber station  500 , including a linear amplification system  10 , according to the present invention. The subscriber station  500  shown in FIG. 6 includes a user interface  502  to the subscriber station. Such an interface  502  may include an ordinary telephone connection, a wireless connected remote user interface, a subscriber relay station, or a radio-connected telephone or mobile station. The user interface  502  is coupled to a subscriber line interface system, which facilitates communication between the user interface  502  and the subscriber station  500 . The line interface system  504  is coupled to an analog-to-digital conversion system  506 , which converts the communication from the user interface  502  (analog) to a digital signal. The analog-to-digital conversion system  506  is coupled to a modulation system  508 , which modulates the digital signal output of the conversion system  506  in a preselected manner. The modulation system  508  is coupled to a linear amplification system  10  embodying the present invention. The amplification system  10  amplifies the modulated signal according to the present invention. The linear amplification system is coupled to a radio system/antenna circuitry  510 . The radio system  510  prepares the amplified signal for transmission using the antenna  512 , which is coupled to the radio system  510 .  
         [0056]    The general controller  518  monitors and controls all of the components of the subscriber station  500 . The general controller  518  is coupled to the components by a control circuit  516 . The subscriber station  500  is coupled to a power supply system  520 , which provides the power required by the station  500  for operation.  
         [0057]    The foregoing is provided for purposes of explanation and disclosure of a preferred embodiment of the present invention. Modifications and adaptations to the described embodiment will be apparent to those of ordinary skill in the art and may be made without departing from the scope or spirit of the invention and the following claims.