Abstract:
Wireless communication device antenna matching circuit tuning responsive to power control signals, and, optionally, responsive to received signal quality indicators in a traffic channel. Systems and methods are provided that increase the antenna efficiency in either the transmit frequency or the receive frequency as needed, based on fading and environmental conditions, non-ideal antenna efficiency balance, mobile station forward versus reverse link usage and system forward versus reverse link usage. The antenna efficiency may be changed incrementally or may be optimized completely for the transmit frequency or the receive frequency. The re-balancing is accomplished by tuning the antenna matching circuit. One way to tune the antenna matching circuit is to apply a voltage to a ferro-electric capacitor in the matching circuit, thereby changing the capacitance of the ferro-electric capacitor, thereby changing the impedance of the antenna system.

Description:
RELATED APPLICATIONS 
     This application relates to the following two U.S. patent applications filed on the same day, having the same inventors, and assigned to the assignee of the present invention, and which are hereby incorporated herein by reference: “MOBILE STATION ACCESS AND IDLE STATE ANTENNA TUNING SYSTEMS AND METHODS”, Ser. No. 11/062,242, and “MOBILE STATION ACQUISITION STATE ANTENNA TUNING SYSTEMS AND METHODS”, Ser. No. 11/062,214. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to wireless electronic communications and more particularly to antenna tuning systems and methods. 
     2. Background 
     In a communication system with different transmit and receive frequencies, mobile station antenna efficiency is a balance between optimization for the transmit frequency and optimization for the receive frequency. Under typical operating conditions, the typical antenna efficiency balance allows for the best use of the transmit and receive resources. However, commonly, conditions occur in which the typical antenna efficiency balance is not preferred. In such conditions, it can be said that the forward and reverse links are not balanced. 
     The forward link is the communication link for data (voice data or other data) travelling from a base station transmitter to a mobile station receiver. The reverse link is the communication link for data (voice data or other data) from the mobile station transmitter to the base station receiver. 
     A first example of a forward and reverse link imbalance is when fading conditions may reduce either the forward link or the reverse link reception. In a second example, the antenna efficiency balance between the transmit and receive frequencies may not be ideal, as a result of some slowly changing parameter or even as a result of a fixed parameter. For example, the antenna matching circuit, or some other hardware component, may have been manufactured or calibrated in a way that provides a non-ideal balance between the transmit and receive frequencies. Alternatively, the antenna efficiency balance may become non-ideal under certain temperature conditions, such as, for example, when high temperatures result from extended continuous use. 
     In a third example, the forward and reverse link may become imbalanced as a result of performance reduction caused by environmental changes around the mobile station. For example, the antenna may be covered by the user&#39;s hand or the mobile station may be placed on a metallic table. 
     In a fourth example, the typical antenna efficiency balance may not be preferred because of the forward and reverse link loading of the communication system at a particular time. For example, the mobile station may be transmitting or receiving only for some time periods. As another example, the wireless communication system may be overloaded in the forward link relative to the reverse link at a particular time. The communication system might be overloaded in the forward link if, for example, data is being transmitted from a base station simultaneously to many users, but relatively few users are transmitting data to the base station. 
     SUMMARY OF THE INVENTION 
     The balance between the forward and reverse link is improved by tuning an antenna matching circuit responsive to reverse power control signals (bits), and optionally, responsive to received signal quality indicators, such as received signal strength indicator (RSSI) and forward frame error rate (FER), or optionally, responsive to forward power control signals (bits). When the forward link is degraded due to fading conditions, the antenna efficiency is increased in the receive frequency, even though doing so may degrade the antenna efficiency in the transmit frequency. Conversely, when the reverse link is degraded due to fading conditions, the antenna efficiency is increased in the transmit frequency, even though doing so may degrade the antenna efficiency in the receive frequency. 
     When a non-ideal antenna efficiency balance between transmit and receive occurs, the balance is restored by re-tuning the antenna efficiency. When mobile station or system reverse and forward link usage is imbalanced, the antenna efficiency balance can be shifted toward either the transmit or receive frequency, depending upon where increased efficiency is needed. For example, if a mobile station is transmitting only, the antenna efficiency balance can be shifted toward the transmit frequency. The antenna efficiency may be shifted a small amount or a large amount toward the transmit frequency. The antenna efficiency may even be optimized completely for the transmit frequency. As another example, if the communication system is heavily loaded on the forward link compared to the reverse link, the antenna efficiency balance of the mobile station may be shifted toward the receive frequency band. 
     The antenna efficiency balance is tuned by tuning the antenna matching circuit. One way to tune the antenna matching circuit is to apply one or more voltages to one or more ferro-electric capacitors in the matching circuit, thereby changing the capacitance of the ferro-electric capacitor(s), thereby changing the impedance of the antenna system (antenna and matching circuit). 
     Other aspects, advantages, and novel features of the invention will become apparent from the following Detailed Description of Preferred Embodiments, when considered in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the present inventions taught herein are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which: 
         FIG. 1  is a block diagram illustrating a wireless communication device tuning an antenna match responsive to a reverse power control signal. 
         FIG. 2  is a plot illustrating a tunable antenna efficiency. 
         FIG. 3  is a flow chart illustrating a method for tuning an antenna efficiency responsive to a reverse link power control parameter, a received signal strength indicator and a frame error rate. 
         FIG. 4  is a flow chart illustrating a method for tuning an antenna efficiency responsive to a reverse link power control parameter and a forward link power control parameter. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a block diagram illustrating a wireless communication device tuning an antenna match responsive to a power control signal. Wireless communication device  100  may be a cellular telephone for communicating with a base station, such as, for example, a code division multiple access (CDMA) mobile station. However, wireless communication device  100  may be any wireless communication device that receives power control signals from the communication system and communicates in at least two frequency bands. U.S. Pat. No. 6,788,685 B1 to Holtzman, which is hereby incorporated by reference, describes methods and systems for controlling transmission power in a closed loop power control system. 
     Wireless communication device  100  includes antenna  102  for radiating electromagnetic signals into the air and for receiving electromagnetic signals from the air. Only one antenna  102  is shown, though multiple antennas are possible. Antenna  102  is connected to tunable matching circuit  104 . Tunable matching circuit  104  may be a ferro-electric tunable matching circuit as described in any of co-pending U.S. patent application Ser. Nos. 10/899,218; 10/899,278; 10/899,285; each filed Jul. 26, 2004; and Ser. No. 10/806,763, filed Mar. 22, 2004, which are each hereby incorporated by reference. Alternatively, tunable antenna matching circuit may be tunable by means of a varactor diode, micro-electrical mechanical switches switching various reactive components in and out of matching circuit  104 , or by any other convenient means of tuning matching circuit  104 . Thus, tunable matching circuit  104  may be a switchable matching circuit. 
     Matching circuit  104  is connected to duplexer  106 . Duplexer  106  duplexes transmit and receive signals. Alternatively, duplexer  106  could be a switch for duplexing transmit and receive signals. Duplexer  106  is connected to transmit path  107 , represented by power amplifier (PA)  108 . Duplexer  106  is also connected to receive path  109 , represented by low noise amplifier (LNA)  110 . Transmit path  107  and receive path  109  are connected to processor  115 . Processor  115  may be a Qualcomm™ mobile station modem (MSM), such as a commercially available Qualcomm™ 6000 series MSM, for CDMA communications. 
     Processor  115  includes controller  120 . Processor  115  demodulates the received signal on receive path  109 . Reverse power control bits are included in the received signal. That is, a base station (not shown) transmits power control bits to mobile station  100 . User interface devices, such as speaker  154 , microphone  157 , display  160  and keypad  163  are also connected to processor  115 . 
     In one embodiment, the mobile station  100  communicates in an IS-2000 cellular communication system. See TIA/EIA/IS-2000, New York, N.Y., USA. The transmit power from the mobile station is determined by the summation of two components, the open loop power control and the closed loop power control. In the open loop power control the mobile station uses the total received power at the mobile station to adjust its own transmit power; the stronger the received power, the lower the mobile station&#39;s transmitter power. Reception of a strong signal from the cell site indicates that the mobile station is either close to the cell site or has an unusually good path to the cell site. 
     The open loop power control mechanism provides for very rapid response over a period of just a few microseconds. In the closed-loop power control (typically used in the traffic state), the base station sends reverse power control bits on the forward power control subchannel to the mobile station to adjust the transmit power of the mobile station in addition to the transmit power determined by open loop power control. Closed-loop power control takes into account sudden degradation and improvement of signals that only affects the reverse link. It also takes into account the independence of Rayleigh fading on the forward link and the reverse link which the mobile station cannot estimate. Ultimately, the closed-loop power control adjustments are limited by the power amplifier and the antenna efficiency of the mobile station on the reverse link. In the closed-loop power control, the reverse power control bit received at the mobile may be accumulated as a transmit gain adjust signal in the mobile station, because the base station is telling the mobile station how to adjust the transmit gain of the mobile station. 
     The base station sends transmit gain adjust signals (also known as power control bits) to the mobile station typically every 1.25 milliseconds (ms). The transmit gain adjust signals are summed together. The transmit gain adjust signals typically take the form of up and down signals. The base station tells the mobile station to turn its transmit power up one unit or down one unit. The reverse power control bit step sizes are typically 1.0 dB. The mean pilot channel output power in dBm is governed by Equation 1, which follows:
 
mean pilot channel output power (dBm)=−mean in input power+offset power+interference correction+ACC 13  CORRECTIONS+RLGAIN 13  ADJs+sum of all closed loop power control corrections.  Equation 1
 
     The following are definitions of the terms in Equation 1, above: 
     mean pilot channel output power: the average transmit power of the reverse pilot channel; 
     mean input power: the total received calorimetric power measured in a specified bandwidth at the antenna connector, including all internal and external signal and noise sources; 
     offset power: the turn around constant (expressed without units) used by the mobile station to determine the transmit power of the mobile station in relation to the received power at the mobile station&#39;s antenna connector; the offset power is defined in TIA/EIA/IS-2000 according to a particular modulation scheme and band class (frequency) of operation; as an example, in the cellular band (800 MHz), the offset power is either −73 or −81.5 depending on which modulation scheme is used; 
     interference correction: min(max(-7-ECIO, 0), 7), where ECIO is the Ec/Io (dB) per carrier of the strongest active set pilot, measured within 500 ms; the mobile station determines Ec/Io (dB) by taking the ratio of the received pilot energy per chip, Ec, to the total received power spectral density (noise and signals), of at most k usable multipath components, where k is the number of demodulating elements supported by the mobile station; the mobile determines the total received power spectral density, Io, over 1.23 MHz; 
     ACC 13  CORRECTIONS: a correction factor which includes additional power offsets determined by the base station and sent as overhead messages to all mobile stations (i.e. NOM 13  PWR, INIT 13  PWR, NOM 13  PWR 13  EXT); 
     RLGAIN 13  ADJs: Gain adjustment applied to the Traffic Channel output power relative to the transmission power on the Access Channel, Enhanced Access Channel, or Reverse Common Control Channel; and 
     sum of all closed loop power control corrections: the sum of all the reverse power control bits send by one or more base stations in the mobile station&#39;s active set. 
     Advantageously, the sum of all transmit gain adjust signals is kept by controller  120  or eslewhere in processor  115 . The sum will be referred to herein as TGA. TGA is an input to a method or table, as will be described in detail below. 
     Another input used by controller  115  is received signal strength indicator (RSSI). RSSI is equal to received power multiplied by the combined pilot energy per chip (Ec) divided by the total received power spectral density (noise, signal and interference), known as I o . 
     Controller  120  may include one or more of main input/output table,  125 , optimum transmit (Tx) table  130 , optimum receive (Rx) table  135 , and transmit/receive (Tx/Rx) table  140 . Controller  120  Tables  125 ,  130 ,  135  and  140  are used to control antenna matching circuit  104 . 
     Main input/output table, e.g., Table 1, below, shows examples of transmit gain adjust (TGA) and received signal strength indicator (RSSI) inputs and corresponding antenna matching outputs. There are many other possibilities. Table 1 is shown merely as an example. Particularly, the values in Table 1 may be optimally determined by experiment, and other rows may be added to Table 1 as a result of experimental determinations. 
     
       
         
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 TGA 
                 RSSI (dBm) 
                 Output 
               
               
                   
                   
               
             
             
               
                   
                 &gt;=7 
                 &gt;−80 
                 Optimum Tx 
               
               
                   
                 5 to 6 
                 &gt;−85 
                 Move 3 bins toward Tx 
               
               
                   
                 4 
                 &gt;−85 
                 Move 2 bins toward Tx 
               
               
                   
                 3 
                 &gt;−85 
                 Move 1 bin toward Tx 
               
               
                   
                 −5 to −6 
                 &lt;−85 
                 Move 1 bin toward Rx 
               
               
                   
                 &lt;=−7 
                 &lt;−90 
                 Optimum Rx 
               
               
                   
                   
               
             
          
         
       
     
     Controller  120  keeps track of the sum of all of the transmit gain adjust commands received from the base station. The TGA column of Table 1 shows values of the sum of all of the transmit gain adjust commands. If, for example, TGA is greater than or equal to seven and RSSI is greater than −80 dBm, then the mobile station sets its antenna matching circuit to the optimum Tx setting. The optimum Tx setting is based on the transmit channel being used and the temperature. The optimum transmit setting may be stored in a table like Table 2, below. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                 Matching Circuit Setting 
               
               
                 Channel or Group 
                 Temperature (° C.) 
                 (Volts) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 &lt;0 
                 0.52 
               
               
                 1 
                  0 to 35 
                 0.26 
               
               
                 1 
                 35 to 60 
                 0.12 
               
               
                 1 
                 &gt;60 
                 0.0 
               
               
                 2 
                 &lt;0 
                 0.80 
               
               
                 2 
                  0 to 35 
                 0.64 
               
               
                 2 
                 35 to 60 
                 0.50 
               
               
                 2 
                 &gt;60 
                 0.38 
               
               
                   
               
             
          
         
       
     
     In Table 2, the voltage decreases with increasing temperature because FE capacitors generally decrease their capacitance with both temperature and voltage. To compensate for increased temperature the voltage is decreased. Further, in Table 2, the voltage increases with increasing channel or group number. The relationship between voltage and channel or group number depends on the particular matching circuit topology chosen and the position of the FE capacitors in the matching circuit. See, for example, the above-referred patent application Ser. Nos. 10/899,218; 10/899,278; 10/899,285; and 10/806,764. 
     Table 2 is stored in a memory of the mobile station, and referred to whenever called by the output of Table 1. In Table 2, only two transmit channels are shown for illustration. In practice many more channels will be stored. Further, the channel designations shown in Table 2 may not be actual transmit channels. Instead, the channel designations may refer to groups of channels. For example, the lowest 200 channels may be designated as channel (or group) 1 in Table 2. The second group of 200 channels may be designated as channel (or group 2) in Table 2. Thus, the lowest 200 channels may have the same matching circuit setting, for any given temperature. 
     Thus, to continue the example above, if TGA is 7 and RSSI is greater than −80 dBm, controller  125  determines from Table 1 that optimum Tx setting should be used. Controller looks optimum Tx setting up in Table 2, based on the temperature and the current transmit channel or group of channels. If, for example, the current Tx channel is channel 1 and the current temperature is 30° C., then controller  125  determines, based on Table 2, that the matching circuit setting is 0.12 Volts. Actual values for the matching circuit settings in Tables 2-4 will be determined experimentally. 
     Processor  115  is connected to matching circuit  104  by control line  142 . Control line  142  supplies a control voltage to matching circuit  104 , such as, for example, 0.12 Volts in the above example. A separate voltage source (not shown) may be provided for supplying the control voltage to matching circuit  104 . Or, as shown, the control voltage is supplied by processor  115  directly, responsive to the output of Table 2, 3 or 4, as determined by controller  120 . Multiple control lines may be used to control multiple matching circuits or multiple matching circuit components, such as multiple FE capactors. 
     Controller  120  is shown internal to processor  115 . In practice, controller may be external or partially external to processor  115 . A separate controller may be provided. For example, a controller may be a separate integrated circuit or may include one or more discrete components. In that case, processor  115  would provide the power control bits or TGA to controller externally. Additionally, RSSI may be provided to controller externally, that is, directly from an RSSI detector (not shown) to controller or from processor to controller. 
     Processor  115  is connected to memory  144 . Tables 1-4 are shown internal to controller  120 , which is shown internal to processor  115 . Tables 1-4 may be stored in memory  144 . Tables 1-4 are shown internal to controller  120  for illustration, since controller uses Tables 1-4 to look up matching circuit settings. 
     Optimum receive matching circuit settings are stored in memory  144  in a table such as Table 3, below, and referred to whenever the output of Table 1 calls for optimum receive settings. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                   
                   
                 Matching Circuit Setting 
               
               
                 Channel or Group 
                 Temperature (° C.) 
                 (Volts) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 &lt;0 
                 2.52 
               
               
                 1 
                  0 to 35 
                 2.26 
               
               
                 1 
                 35 to 60 
                 2.12 
               
               
                 1 
                 &gt;60 
                 2.0 
               
               
                 2 
                 &lt;0 
                 2.60 
               
               
                 2 
                  0 to 35 
                 2.44 
               
               
                 2 
                 35 to 60 
                 2.30 
               
               
                 2 
                 &gt;60 
                 2.18 
               
               
                   
               
             
          
         
       
     
     Table 3 is stored in a memory of the mobile station, and referred to whenever called by the output of Table 1. In Table 3, only two receive channels are shown for illustration. In practice many more channels will be stored. Further, the channel designations shown in Table 3 may not be actual channels. Instead, the channel designations may refer to groups of channels. For example, the lowest 200 channels may be designated as channel (or group) 1 in Table 3. The second group of 200 channels may be designated as channel (or group 2) in Table 3. Thus, the lowest 200 channels may have the same matching circuit setting, for any given temperature. 
     Another table, such as Table 4, stores matching circuit settings for moving stepwise toward better transmit matching or stepwise toward better receive matching. Stepwise movement is used when the output of Table 1 is something other than Optimize Tx or Optimize Rx. For example, according to Table 1, if TGA is 5 or 6 and RSSI is &gt;85 dBm, then the mobile station tunes the antenna matching circuit  3  steps in the transmit direction (e.g., lower frequency in the U.S. CDMA, higher frequency in Japan CDMA). An example Table 4 is shown below. As is the case for Tables 1-3, experiment will give 4. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 Bin Number 
                 Matching Circuit Setting (Volts) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1 
                 0.0 
               
               
                   
                 2 
                 0.13 
               
               
                   
                 3 
                 0.26 
               
               
                   
                 4 
                 0.38 
               
               
                   
                 5 
                 0.50 
               
               
                   
                 6 
                 0.62 
               
               
                   
                 7 
                 0.73 
               
               
                   
                 8 
                 0.83 
               
               
                   
                   
               
             
          
         
       
     
     Table 4 does not include temperature as a parameter. Temperature may be included, increasing the complexity and accuracy of Table 4. Further, only eight bins are shown in Table 4. In practice, many more bins are recommended. 
     As described above, controller  120  determines a matching circuit setting for matching circuit  104 .  FIG. 2  is a plot illustrating a tunable antenna efficiency which can be tuned responsive to the determined matching circuit setting. Antenna efficiency  147  is plotted against frequency  150 . An example antenna efficiency  153  is shown as curve  153 . Antenna efficiency  153  can be tuned by tuning matching circuit  104 . As matching circuit  104  is tuned, curve  153  can be moved to higher or lower frequencies, as shown by arrows  156  and  159 . As described in the above referenced copending U.S. patent application Ser. Nos. 10/899,278 and 10/899,218, curve  153  may be tuned to provide maximum efficiency for the currently used transmit and receive channels. Further, curve  153  is tuned responsive to commands from controller  120 , based on Tables 1-4. 
     For example, if Table 1 calls for an optimum Tx setting, controller retrieves the optimum Tx setting from Table 2, and tunes curve  153 , so that peak  162  is positioned at the frequency corresponding to the current Tx channel or group of channels and the current temperature. Advantageously, the antenna efficiency is improved in the current Tx channel when improved Tx efficiency is necessary. In such a case, the Rx antenna efficiency will be degraded, but this occurs at a time when Rx antenna efficiency is not needed. As described above, the optimum Tx matching circuit efficiency is selected only when the reverse link (transmission from the mobile station) is doing poorly and the forward link (reception a the mobile station) is doing well. The reverse link and the forward link are rebalanced at least to some extent. System resources are more optimally utilized. 
     As described above with respect to Tables 1 and 3, if the reverse link is doing well and the forward link is doing poorly, an optimum Rx matching circuit setting will be selected from Table 3. Matching circuit  104  is tuned to move peak  162  of curve  153  to the frequency of the current Rx channel or group of channels. 
     As described above with respect to Tables 1 and 4, if a shift in matching circuit setting is called for other than an optimum Tx or Rx setting, then a matching circuit setting will be selected from Table 4. Controller  120  keeps track of which bin the matching circuit setting is currently in. Then, when Table 1 calls for a shift based on Table 4, controller  120  looks up the new matching circuit setting in Table 4, based on the current bin, the number of bins to move and the direction (Tx or Rx). For example, if the current matching circuit setting is 0.13 Volts, that is, bin number  2 , and Table 1 calls for a shift of 2 bins toward Rx then controller  120  will look up bin  4  (start at bin  2  and add 2 bins for the selected 2 bin shift) and find the matching circuit setting corresponding to bin  4 , which in this case is 0.38 Volts. Controller  120  will tune matching circuit  104  by applying 0.38 Volts to matching circuit  104 , thereby moving curve  153  two bins toward the Rx frequencies. 
       FIG. 3  is a flow chart illustrating a method for tuning an antenna efficiency (such as curve  153  in  FIG. 2 ) responsive to a reverse link power control parameter (such as TGA), RSSI and FER. The method starts in step  165 . In step  170 , the mobile station enters a traffic state. Traffic state means that the mobile station is sending or receiving data (which may be voice data or other data) in a traffic channel. In decision step  180 , the mobile station determines whether TGA is greater than or equal to −5 and less than or equal to 5. If not, then TGA is outside the range of −5 to 5. When TGA is within the range between −5 and 5 the reverse link in this example is considered to be operating in the desired range. If TGA is below −5 the reverse link is considered to be favorable whereas when TGA is above 5 the reverse link is operating unfavorably. 
     If TGA is outside the range −5 to 5, the next step is decision step  185 , in which the mobile station determines whether TGA is greater than 5. If not, that means TGA is less than −5 and the next step is step  190 , in which the antenna efficiency is shifted toward the Rx frequencies. Advantageously, the quality of the forward link is improved, thereby improving the coverage of the cell for the mobile station and the efficiency of network resource use. After step  190 , the method returns to step  180 . 
     If TGA is greater than 5, then the next step is decision step  195 , in which it is determined whether the FER is less than one percent. If not, the method follows the “NO” path from step  195  and returns to step  180 . This indicates that although the reverse link is poor, the forward link is also poor; therefore, adjusting the bias in antenna efficiency in either direction would not be desirable. It is also possible to adjust the matching circuit even if both the forward and the reverse links are doing poorly, but such systems and methods are not described further here. 
     But if the FER is less than one percent, then the next step is decision step  200 , in which it is determined whether RSSI is greater than −85 dBm. If not, the method follows the “NO” path from step  195  and returns to step  180 . But if the RSSI is greater than −85 dBm, then the next step is step  205 , in which the antenna efficiency is shifted toward the Tx frequencies. After step  205 , the method returns to step  180 . 
     Returning to the discussion of step  180 , if TGA is in the range of −5 to 5, then the next step is decision step  210 , in which it is determined whether the FER is less than one percent. If not, then the next step is step  215 , in which the antenna efficiency is shifted toward the Rx frequencies. 
     But if the FER is less than one percent, then the next step is decision step  220 , in which it is determined whether RSSI is greater than −85 dBm. If not, then the next step is step  215 , in which, as stated above, the antenna frequency is shifted toward the Rx frequencies. But if RSSI is greater than −85 dBm, then the method returns to step  180 . This indicates that both the forward and reverse links are in good condition; therefore, adjusting the antenna efficiency in either direction is not needed. 
     The shifting of antenna efficiency of steps  190 ,  205  and  215  can be accomplished by any convenient means, such as, for example, by employing a table like Table 4. Thus, the method described with respect to  FIG. 3  may be accomplished using Table 4 and without Tables 1-3. Alternatively, even Table 4 may be avoided if, for example, the matching circuit settings are all equally spaced. Then, the shift steps  190 ,  205  and  215  may be accomplished without Table 4, merely by changing the matching circuit setting by a predetermined amount in either the Tx or the Rx direction. For example, responsive to steps  190  and  215 , 0.1 Volt may be added to the current matching circuit setting, while, responsive to step  205 , 0.1 Volt may be subtracted from the current matching circuit setting. 
     While FER and RSSI are shown in  FIG. 3 , any received signal quality indicator can be used. Further, the method may include only one received signal quality indicator, such as FER or RSSI, or another received signal quality indicator. For example, symbol error rate (SER) or message error rate (MER) can be used. But if SER is used in a system such as TIA/EIA/IS-95 or IS-2000, then the gain of the decoder will not be accounted for. In CDMA systems, such as those described in TIA/EIA/IS-2000, a convolutional encoder takes a block of bits (e.g., 194 bits, including tail bits) in a 20 ms frame and, depending on the rate of the encoder, produces varying numbers of symbols (e.g., 394, for half rate encoding). Symbol errors are determined prior to running the decoder since the decoder would need, e.g., all 394 symbols, to decode the symbols into the original information bits. Thus, SER could be used. Since SER is faster than FER, SER might be ideal for the case of improving the capacity of the wireless communication system. 
     The thresholds (e.g., TGA=5 and −5, RSSI=−85 dBm) shown in  FIGS. 3 and 4  may be other numbers than shown. For example, if the mobile stations in a commercial wireless communication network commonly operate with an average TGA of 5, and 5 is considered the appropriate balance for the specific network, then 5 can be added to the TGA thresholds in  FIG. 3 , such that step  180  would say “IS TGA≧0 AND TGA≦10?”. As another example, step  180  could say “IS TGA≧−2 AND TGA≦3?”. In other words, the thresholds can be moved closere together or further apart and they can be shifted. Similar changes can be made throughout  FIGS. 3-4  and Tables 1-4. 
       FIG. 4  is a flow chart illustrating a method for tuning an antenna efficiency (such as curve  153  in  FIG. 2 ) responsive to a reverse link power control parameter (such as TGA) and a foward link power control parameter. In some communication systems, the mobile station sends power control signals to the base station. See, e.g., TIA/EIA/IS-2000. In that case, if the mobile station has told the base station to increase its power many times, while the base station has not told the mobile station to increase its power very many times, there may be an imbalance between the forward link and the reverse link. The forward link is poor and the reverse link is good. In that case, antenna efficiency should be tuned toward the Rx frequencies. 
     Conversely, if the base station has told the mobile station to increase its power many times and the mobile station has not told the base station to increase its power many times, then there may be a different imbalance between the forward link and the reverse link. The forward link is good and the reverse link is poor. In that case, antenna efficiency should be tuned toward the Tx frequencies.  FIG. 4  illustrates a method of rebalancing the forward and reverse link, regardless of which is poor and which is good. 
     The mobile station (in processor  115  or controller  120 ) keeps track of the sum of all foward link power control signals sent by the mobile station to the base station. This sum is referred to herein as reverse gain adjust (RGA). 
     The method of  FIG. 4  starts in step  224 . In step  228 , the mobile station enters a traffic state. In decision step  232 , it is determined whether TGA is less than or equal to 5. If not, then the next step is decision step  240 , in which it is determined whether RGA is less than or equal to 5. If not, then the method returns to step  232 . But if RGA less than or equal to 5, then the next step is step  244 , in which the antenna efficiency is shifted toward the Tx frequencies. Advantageously, the forward and reverse links are rebalanced at least to some extent. Network resources are used more efficiently. After step  244 , the method returns to step  232 . 
     Returning to the discussion of step  232 , if TGA is less than or equal to 5, then the next step is decision step  248 , in which it is determined whether RGA is greater than or equal to 5. If so, then the next step is step  252 , in which the antenna efficiency is shifted toward the Rx frequencies. Advantageously, the forward and reverse links are rebalanced at least to some extent. Network resources are used more efficiently. After step  252 , the method returns to step  232 . If RGA is not greater than or equal to 5, then the method returns to step  232 . 
     Further, while embodiments and implementations of the invention have been shown and described, it should be apparent that many more embodiments and implementations are within the scope of the invention. Accordingly, the invention is not to be restricted, except in light of the claims and their equivalents.