Patent Publication Number: US-2010111221-A1

Title: Optimized digital correction for power amplifier distortion and quadrature error

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to the field of wireless communications, and more particularly relates to managing signal distortion and errors in complex transmitter systems. 
     BACKGROUND OF THE INVENTION 
     Wireless devices include one or more transmitters for transmitting data signals. One type of transmitter is a complex transmitter, which implements a quadrature modulator. These types of transmitters experience various signal distortions from the transmitter components such as power amplifiers and the quadrature modulator. Conventional methods used for correcting these signal distortions generally require factory calibration of the transmitter. However, as the components within the transmitter age or as the environment changes the transmitter usually needs to be recalibrated. This generally requires a technician to come out to the transmitter or for the transmitter to be sent back to the factory. Each of these options is time consuming and can cause the wireless device to experience unnecessary down time. 
     SUMMARY OF THE INVENTION 
     In one embodiment, a new and novel method manages quadrature and non-linear distortions in a transmitter system. The method includes generating a transmit data signal at an output of a transmitter amplifier from a baseband data signal. The transmit data signal can include one or more distortions selected from the set of: Non-linear distortions, Q-offset, I-offset, Quadrature imbalance, and Scaling. A radio frequency (“RF”) receiver circuit receives the transmit data signal generated at the output of the transmitter amplifier. A received signal is generated at an output of the RF receiver circuit that comprises a digital representation of the received transmit data signal. The received signal is statistically analyzed. A representation of each distortion of the one or more distortions is identified in the transmit data signal in response to statistically analyzing the received signal. At least one information signal comprising an information set of distortion adjustments associated with a representation of at least one of the one or more distortions in the transmit data signal is generated in response to the identifying. Distortion of the transmit data signal is adjusted based on the information set of distortion adjustment in the at least one information signal. The adjusting reduces the at least one of the one or more distortions in the transmit data signal. 
     In another embodiment, a wireless device that manages quadrature and non-linear distortions in a transmitter is disclosed. The wireless device comprises a memory and a processor that is communicatively coupled to the memory. The wireless device also includes at least one transmitter that is communicatively coupled to the memory and the processor. The at least one transmitter comprises a distortion manager and a radio frequency (“RF”) receiver circuit. The at least one transmitter is adapted to generate a transmit data signal at an output of a transmitter amplifier from a baseband data signal. The transmit data signal can include one or more distortions selected from the set of: Non-linear distortions, Q-offset, I-offset, Quadrature imbalance, and Scaling. The RF receiver circuit is adapted to receive the transmit data signal generated at the output of the transmitter amplifier. A received signal is generated at an output of the RF receiver circuit that comprises a digital representation of the received transmit data signal. The distortion manager is adapted to statistically analyze the received signal. The distortion manager identifies a representation of each distortion of the one or more distortions in the transmit data signal in response to statistically analyzing the received signal. The distortion manager, in response to the identifying, generates at least one information signal comprising an information set of distortion adjustments associated with a representation of at least one of the one or more distortions in the transmit data signal. The distortion manager then adjusts distortion of the transmit data signal based on the information set of distortion adjustment in the at least one information signal. The adjusting reduces the at least one of the one or more distortions in the transmit data signal. 
     In yet another embodiment, a wireless communication system that manages quadrature and non-linear transmit signal distortions is disclosed. The wireless communication system comprises at least one wireless network. At least one wireless device is communicatively coupled to the at least one wireless network. The wireless device comprises a memory and a processor that is communicatively coupled to the memory. The wireless device also includes at least one transmitter that is communicatively coupled to the memory and the processor. The at least one transmitter comprises a distortion manager and a radio frequency (“RF”) receiver circuit. The at least one transmitter is adapted to generate a transmit data signal at an output of a transmitter amplifier from a baseband data signal. The transmit data signal can include one or more distortions selected from the set of: Non-linear distortions, Q-offset, I-offset, Quadrature imbalance, and Scaling. The RF receiver circuit is adapted to receive the transmit data signal generated at the output of the transmitter amplifier. A received signal is generated at an output of the RF receiver circuit that comprises a digital representation of the received transmit data signal. The distortion manager is adapted to statistically analyze the received signal. The distortion manager identifies a representation of each distortion of the one or more distortions in the transmit data signal in response to statistically analyzing the received signal. The distortion manager, in response to the identifying, generates at least one information signal comprising an information set of distortion adjustments associated with a representation of at least one of the one or more distortions in the transmit data signal. The distortion manager then adjusts distortion of the transmit data signal based on the information set of distortion adjustment in the at least one information signal. The adjusting reduces the at least one of the one or more distortions in the transmit data signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying figures where like reference numerals refer to identical or functionally similar elements throughout the separate views, and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention. 
         FIG. 1  is block diagram illustrating an operating environment according to one embodiment of the present invention; 
         FIG. 2  is a block diagram illustrating a detailed view of a transmitter according to one embodiment of the present invention; 
         FIGS. 3-4  are operational flow diagrams illustrating one example of continuously and autonomously managing/optimizing non-linear and quadrature distortions in a transmit data signal according to one embodiment of the present invention; and 
         FIG. 5  is a block diagram illustrating a detailed view of a wireless device according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely examples of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting; but rather, to provide an understandable description of the invention. Additionally, the invention shall have the full scope of the claims and shall not be limited by the embodiments shown below. 
     The terms “a” or “an”, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language). The term coupled, as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically. It is further understood that the use of relational terms, if any, such as first, second, top and bottom, front and rear, and the like are used solely for distinguishing one entity or action from another, without necessarily requiring or implying any such actual relationship or order between such entities or actions. 
     For purposes of this application the term “wireless device” is intended to broadly cover many different types of devices that can wirelessly transmit signals, and optionally can wirelessly received signals, and may also operate in a wireless communication system. For example, and not for any limitation, a wireless device can include (but is not limited to) any one or a combination of the following: a transmitter basestation, a two-way radio, a cellular telephone, a mobile phone, a smartphone, a two-way pager, a wireless messaging device, a laptop/computer, automotive gateway, or a residential gateway. 
     According to one embodiment of the present invention as shown in  FIG. 1  one example of a wireless communication system  100  is illustrated. In particular,  FIG. 1  shows one or more wireless devices  102 ,  104  communicatively coupled to one or more wireless communication networks  106 . Each wireless device  102 ,  104  includes one or more transmitters  108 . In one embodiment, the transmitters  108  are zero intermediate frequency transmitters. However, the present invention is also applicable to any type of transmitter with a quadrature modulator or any complex intermediate frequency system as well. The transmitter  108  includes a distortion manager  110 . The distortion manager  110  automatically and continuously corrects non-linear and quadrature distortions without the need for factory calibrations. The distortion manager  110  is discussed in greater detail below. 
     It should be noted that although  FIG. 1  shows two wireless devices, the wireless communication system  100  supports any number of wireless devices  102 ,  104 , which can be single mode or multi-mode devices. Multi-mode devices are capable of communicating over multiple access networks with varying technologies. For example, a multi-mode wireless device can communicate over various access networks such as GSM, UMTS, CDMA, or WiFi. In addition, multiple communication protocols such as Push-To-Talk (PTT), Push-To-Talk Over Cellular (PoC), voice traffic channel, multimedia messaging, web browsing, Voice over IP (VoIP), and multimedia streaming may be utilized. 
     The wireless communication network  106  can include one or more networks such as a circuit service network and/or a packet data network. The communication network  106  can either be wired or wireless. The wireless communications standard of the network  106  can comprise Code Division Multiple Access (“CDMA”), Time Division Multiple Access (“TDMA”), Global System for Mobile Communications (“GSM”), General Packet Radio Service (“GPRS”), Frequency Division Multiple Access (“FDMA”), other IEEE 802.16 standards, Orthogonal Frequency Division Multiplexing (“OFDM”), Orthogonal Frequency Division Multiple Access (“OFDMA”), Wireless LAN (“WLAN”), WiMAX, or the like. The wireless communication network  106  is able to include an IP or SIP based connectivity network, which provides data connections at much higher transfer rates then a traditional circuit services network. These networks are able to comprise an Evolution Data Only (“EV-DO”) network, a General Packet Radio Service (“GPRS”) network, a Universal Mobile Telecommunications System (“UMTS”) network, an 802.11 network, an 802.16 (WiMAX) network, Ethernet connectivity, dial-up modem connectivity, or the like. A circuit services network is able to provide, among other things, voice services to the wireless devices  102 ,  104  communicatively coupled to the network  106 . Other applicable communications standards include those used for Public Safety Communication Networks including TErrestrial TRunked rAdio (“TETRA”) and P25 Trunking. It should be noted that these network technologies are only used as an illustrative example and do not limit further embodiments of the present invention. 
     The wireless communication system  100  also includes one or more base stations  112  communicatively coupled to the wireless communication network(s)  106 . Each base station  112  includes one or more transmitters  114 ,  116 . One or more of these transmitters  114 ,  116  can be similar to the transmitter  108  discussed above. For example, one or more of these transmitters  114 ,  116  can include a distortion manager  118 . 
     As discussed above, transmitter systems that implement quadrature modulators experience quadrature distortions/errors that limit vector accuracy and spectral performance. Non-linear distortions/errors are also experienced from power amplifiers within the transmitter systems as well. The transmitter system  108  of the various embodiments of the present invention utilizes a distortion manager  110  that continuously monitors a transmit signal for non-linear distortions created by power amplifiers and quadrature distortions created by a quadrature modulator within the transmitter and adjusts the transmit signal until these distortions reach zero. For example, the distortion manager  110  receives a transmit signal and generates a digital representation of the received signal. The distortion manager  110  then statistically analyzes the received signal and identifies a representation of each distortion within the received signal. An information signal including an information set of distortion adjustments associated with the identified distortion representations is then generated by the distortion manager  110 . The distortion manger  108  based on the information signal then adjusts the distortions of the transmit signal, thereby reducing at least one distortion in the transmit signal. The process can be continually performed by the distortion manager  110  to effectively reduce the distortions of the transmit signal to zero. 
       FIG. 2  shows a more detailed view of a transmitter  108  including a distortion manager  110 . It should be noted that although the above discussion is with respect to a transmit data signal, the various embodiments are also applicable to a received signal as well as noise and can manage transmit/received signal distortions in a single system. It is assumed that the reader is familiar with wireless transmitters. Therefore, to simplify the present discussion, only the portion(s) of a transmitter that is relevant to the various embodiments of the present invention is discussed in detail. In particular,  FIG. 2  shows digital components and analog components of the transmitter  108  separated by the dashed line  201 . The distortion manager  110  shown by a dashed-dotted box, in one embodiment, comprises a non-linear pre-distortion engine or non-linear datapath  208 , a quadrature modulator pre-distortion or QMod compensation datapath  210 , a QMod controller  254 , and a non-linear adaptation module  248 , all of which are discussed in greater detail below. 
       FIG. 2  shows baseband data  202  that represents a transmit data signal that is to be transmitted by the transmitter  108 . As discussed above, the transmitter  108 , in one embodiment, is a complex IF transmitter. Therefore, the transmit data signal  202  comprises an I component  204  and a Q component  206 . The transmitter  108  includes a digital pre-distortion module or non-linear datapath  208  and a quadrature modulator pre-distortion or QMod compensation datapath  210 . The non-linear datapath  208  is a pre-distortion engine (such as a lookup table, etc.) that includes a non-linear distortion adjuster  212  that adjusts the baseband signal  202  to reduce or eliminate non-linear distortions caused by the power amplifier  214 . The QMod compensation datapath  210  includes quadrature distortion adjusters such as a Q-offset adjuster  216 , an I-offset adjuster  218 , a Quadrature imbalance adjuster  220 , and a Scaling adjuster  222  that adjusts the baseband signal  202  to reduce or eliminate quadrature distortions such as Q-offset, I-offset, Quadrature imbalance, and Scaling distortions caused by the quadrature modulator  224 . The non-linear datapath  208 , QMod compensation datapath  210 , and their components are discussed in greater detail below. 
     The pre-distorted I and Q components of the baseband data signal  202  outputted by the QMod compensation datapath  210  are each received by a respective digital-to-analog converter (“DAC”)  226 ,  228 . The output of each DAC  226 ,  228  is then combined by the Qmod  224  with a continuous wave signal generated by a local oscillator  230  to generate a modulated radio frequency (“RF”) signal  232 . An RF amplifier stage(s) including transmitter amplifiers  234  and a power amplifier  214  increases the power level of the modulated RF signal  232  prior to the modulated RF signal  232  being applied to an antenna(s)  236  to generate a transmit data signal  235 . It should be noted that the baseband signal  202 , the modulated radio frequency (“RF”) signal  232 , and the transmit data signal  235  discussed above are all the same signal but at different stages within the transmitter  108 . 
     Receiver circuit(s)  238  receives the transmit data signal  235 . The receiver circuit(s)  238  samples the received transmit data signal  235 . The output of the receiver circuit(s)  238  is mixed down to a given frequency via a mixer  240  electrically coupled to another local oscillator  242  and converted to the digital domain by an analog-to-digital converter (“ADC”)  244  to generate a digital representation  245  of the transmit data signal  235 . It should be noted that the local oscillator  230  electrically coupled to the QMod  224  and the local oscillator  242  electrically coupled to the mixer  240  can be the same oscillator circuit or two oscillator circuits that are separate from each other. 
     If the two local oscillators  230 ,  242  are different from each other then the output of the ADC  244  is received by a digital mixer  246  to bring the frequency of the digital representation signal  245  back to the original frequency of the baseband signal  202 . The output of the digital mixer  246  is received by a non-linear adaptation module  248  that comprises a phase monitor  250 . The non-linear adaptation module  248  identifies non-linear distortion characteristics or representations within the received digital representation signal  245 . The non-linear adaptation module  248 , via the phase monitor  250 , determines the relative phase between the transmitter and receiver portions of the transmitter  108  in response to receiving the digital representation signal  245 . For example, the phase monitor  250  determines the average complex gain between the transmitter and receiver portions of the transmitter  108 . The relative phase is determined because an arbitrary phase shift occurs between the transmitter and receiver portions of the transmitter  108 , which can cause system instability. For example, given a 180 degree phase shift, the received I and Q signals would have their signs flopped. Therefore, the phase monitor  250  uses the following calculation to perform a phase recovery operation 
     
       
         
           
             
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     The results of this calculation are then transmitted to the QMod controller  254  to program a phase shifter  256 . 
     The non-linear adaptation module  248 , in one embodiment, generates an information signal  252  based on the non-linear distortion characteristics or representations that have been identified. This information signal  252  comprises an information set of non-linear distortion adjustments that are to be applied to the baseband signal  202  for reducing or eliminating the non-linear distortions created by the power amplifier  214 . The non-linear adaptation module  248  then transmits this signal  252  to the non-linear datapath  208  discussed above. The non-linear distortion adjuster  212  uses the information set of non-linear distortion adjustments in the information signal  252  to adjust or pre-distort the baseband signal  202  so that non-linear distortions or reduced or are eliminated. For example, the non-linear distortion adjuster  212  of the non-linear datapath  208 , in one embodiment, uses the information set of non-linear distortion adjustments to produce a signal y=f(|x|)*x where y and x are complex valued signals and f(|x|) is an inverse function of the power amplifier  214 . Typically, this can be implemented as a table of gains, indexed by the magnitude of the input signal  202 , multiplied by the input signal  202 . Therefore, the non-linear datapath  208  produces an output signal which is a “pre-distorted” version of the input signal  202 , thereby reducing or eliminating any non-linear distortions added to the transmit data signal  235  by the power amplifier  214 . 
     The phase information is transmitted by the non-linear adaptation module  248  to a QMod controller  254 , which in one embodiment can be implemented in a field programmable array. The QMod controller  254  uses the received phase information to program a phase rotation in a phase shifter  256 . The QMod controller  254  also receives the output of the digital mixer  246  at the phase shifter  256 . The QMod controller  254  statistically analyzes the digital representation signal  245  received from the digital mixer  246  to identify a representation of one or more of the distortions in the transmit data signal  235  created by the QMod. For example, the QMod  224  can create one or more of the following distortions within the transmit data signal  235 : Q-offset, I-offset, Quadrature/Phase imbalance, and Scaling imbalance. Therefore, in one embodiment, the QMod controller  254  statistically analyzes the digital representation signal  245  to identify a representation of one or more of the Q-offset, I-offset, Quadrature/Phase imbalance, and Scaling imbalance distortions. 
     In one embodiment, the QMod controller  254  performs the statistical analysis using one or more filters  258 ,  260 ,  262 ,  264  that receive an output signal from the phase shifter  256 . These filters are a Q-offset filter  258 , an I-offset filter  260 , a Quadrature imbalance filter  262 , and a Scaling imbalance filter  264 . Each filter  258 ,  260 ,  262 ,  264  performs one or more operations on the signal received from the phase shifter  256  and passes an output signal to an information signal generator  266 . 
     The information signal generator  266  takes the results of each filter  258 ,  260 ,  262 ,  264  and generates one or more information signals  268  that includes a signal adjustment information set comprising adjustment information corresponding to one or more of the quadrature distortions (Q-offset, I-offset, Quadrature imbalance, and Scaling imbalance) within the transmit data signal  235 . The signal adjustment information set within the information signal  268  instructs the QMod compensation datapath and the Q-offset adjuster  216 , I-offset adjuster  218 , Quadrature imbalance adjuster  220 , and/or Scaling adjuster  222  how to adjust or pre-distort the baseband data signal  202  so that the Quadrature distortions within transmit data signal  235  are reduced or eliminated. 
     For example, the signal adjustment information set within the information signal  268  can include Q-offset adjustment information, I-offset adjustment information, Quadrature imbalance adjustment information, and/or Scaling imbalance adjustment information. The Q-offset adjuster  216  uses the Q-offset adjustment information to adjust the baseband signal  202  so that Q-offset distortions are reduced or eliminated. The I-offset adjuster  218  uses the I-offset adjustment information to adjust the baseband signal  202  so that I-offset distortions are reduced or eliminated. The Quadrature imbalance adjuster  220  uses the Quadrature imbalance adjustment information to adjust the baseband signal  202  so that Quadrature imbalance distortions are reduced or eliminated. The Scaling adjuster  222  uses the Scaling imbalance adjustment information to adjust the baseband signal  202  so that Scaling imbalance distortions are reduced or eliminated. 
     In particular, the Q and I offset filters  258 ,  260 , which combined create a DC offset filter, perform the following calculation 
     
       
         
           
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     where E is the expected value operator defined by 
     
       
         
           
             
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     is a random process and f x (x) is the probability density function. The variable Y is signal at the output of the Qmod, and c is the value that minimizes DC offset so that adjustment information can be sent to the Q and I offset adjusters  216 ,  218  in the QMod compensation datapath  210  to eliminate/reduce Q and I offset distortions within the transmit data signal  235 . Alternatively, the QMod controller  254  can identify the value or argument of B minimizes E[Y]. Letting Ŷ be the corrected sequence and c be the DC correction factor, a control loop performs the above calculation with the following equation E[Ŷ]=E[Y]−c (EQ 1). The control loop, in one embodiment, is a continuous feedback loop from the receiver  238  into the QMod controller  254  and the non-linear adaptation module  248  that continuously provides data associated with a transmit data signal  235  as input into the QMod controller  254  and the non-linear adaptation module  248  and has as an output information signals comprising distortion adjustment data generated by the QMod controller  254  and the non-linear adaptation module  248 . 
     Using E[Y]=0 as the best minimum results in c=E[Y]. For mean ergodic purposes c is: 
     
       
         
           
             
               
                 
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     For the iterative process of the distortion manager  110  (e.g., the continuous monitoring of signal distortions and adjustment thereof) 
     
       
         
           
             
               
                 
                   
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     is approximated as μ, which is a convergence factor. In one embodiment, the convergence factor μ is set at a small number resulting in c n =μY n +c n−1  (EQ 7). Updating c results in some power being left in the estimate E[Ŷ]. Therefore, the relative level of the offset power relative to the signal power is 
     
       
         
           
             
               
                 
                   
                     
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     In general terms, the limiting dBc of the DC offset is 1/μ. It should be noted that one advantage of this algorithm is that the remaining DC offset energy is spread by the bandwidth of the transmitted signal. Also, since 1/μ is about 1/n the algorithm is as converged as it will be in 1/μ iterations. Therefore, this achieves perfect convergence as μ→0 and n→∞. As a result of the above process, c n =μY n +c n−1  (EQ 7) (which is a combined result of the Q-offset and I-offset filters  258 ,  260 ) is used by the information signal generator  266  to generate an information signal  268  comprising DC offset (i.e., Q-offset and I-offset) distortion adjustment information for the Q-offset and I-offset adjusters  216 ,  218  in the QMod compensation datapath  210 . 
     With respect to Quadrature/Phase imbalance distortions, the Quadrature imbalance filter  262  performs the following calculation 
     
       
         
           
             
               
                 
                   
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     where Y is the signal seen at the output of the QMod and R and I are the real and imaginary operators, so that adjustment information can be sent to the Quadrature/Phase imbalance adjuster  220  in the QMod compensation datapath  210  to eliminate/reduce Quadrature/Phase imbalance distortions within the transmit data signal  235 . Letting α be the phase correction factor, the estimate of the corrected signal is calculated as follows: Ŷ=Y−j (Y)=Y i +j(Y q −αY i ) (EQ 10), where Y i = (Y) and Y q = (Y). Assuming that a minimum of 0 can be obtained for the correlation: E[(Y i )(Y q −αY i )]=0 (EQ 11), E[Y i Y q ]−αE[Y i Y i ]=0 (EQ 12), and 
     
       
         
           
             
               
                 
                   α 
                   = 
                   
                     
                       
                         COV 
                          
                         
                           [ 
                           
                             
                               Y 
                               i 
                             
                              
                             
                               Y 
                               q 
                             
                           
                           ] 
                         
                       
                       
                         VAR 
                          
                         
                           [ 
                           
                             Y 
                             i 
                           
                           ] 
                         
                       
                     
                     . 
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                      
                     
                         
                     
                      
                     13 
                   
                   ) 
                 
               
             
           
         
       
     
     VAR[Y i ] is normalized so that VAR[Y i ]=1 and a is made a series in an iterative process resulting in 
     
       
         
           
             
               
                 
                   
                     α 
                     n 
                   
                   = 
                   
                     
                       1 
                       n 
                     
                      
                     
                       
                         ∑ 
                         
                           r 
                           = 
                           0 
                         
                         n 
                       
                        
                       
                         
                           Y 
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                          
                         
                           
                             Y 
                             qr 
                           
                           . 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                      
                     
                         
                     
                      
                     14 
                   
                   ) 
                 
               
             
           
         
       
     
     Substituting n−1 for n results in 
     
       
         
           
             
               
                 
                   
                     α 
                     
                       n 
                       - 
                       1 
                     
                   
                   = 
                   
                     
                       1 
                       
                         n 
                         - 
                         1 
                       
                     
                      
                     
                       
                         ∑ 
                         
                           r 
                           = 
                           0 
                         
                         
                           n 
                           - 
                           1 
                         
                       
                        
                       
                         
                           Y 
                           ir 
                         
                          
                         
                           
                             Y 
                             qr 
                           
                           . 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                      
                     
                         
                     
                      
                     15 
                   
                   ) 
                 
               
             
           
         
       
     
     Removing a term from the sum results in 
     
       
         
           
             
               
                 
                   
                     α 
                     n 
                   
                   = 
                   
                     
                       
                         1 
                         n 
                       
                        
                       
                         Y 
                         
                           i 
                            
                           
                               
                           
                            
                           n 
                         
                       
                        
                       
                         Y 
                         qn 
                       
                     
                     + 
                     
                       
                         1 
                         n 
                       
                        
                       
                         
                           ∑ 
                           
                             r 
                             = 
                             0 
                           
                           
                             n 
                             - 
                             1 
                           
                         
                          
                         
                           
                             Y 
                             ir 
                           
                            
                           
                             Y 
                             qr 
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                      
                     
                         
                     
                      
                     16 
                   
                   ) 
                 
               
             
           
         
       
     
     and substituting back in yields 
     
       
         
           
             
               
                 
                   
                     α 
                     n 
                   
                   = 
                   
                     
                       
                         1 
                         n 
                       
                        
                       
                         Y 
                         
                           i 
                            
                           
                               
                           
                            
                           n 
                         
                       
                        
                       
                         Y 
                         qn 
                       
                     
                     + 
                     
                       
                         
                           n 
                           - 
                           1 
                         
                         n 
                       
                        
                       
                         
                           α 
                           
                             n 
                             - 
                             1 
                           
                         
                         . 
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                      
                     
                         
                     
                      
                     17 
                   
                   ) 
                 
               
             
           
         
       
     
     Using similar approximations as discussed above, 
     
       
         
           
             
               n 
               
                 n 
                 - 
                 1 
               
             
             = 
             
               1 
                
               
                   
               
                
               and 
                
               
                   
               
                
               
                 1 
                 n 
               
             
           
         
       
     
     as μ results in α n =μY in Y qn +α n−1  (EQ 18). Using similar math and logic as discussed above with respect to the DC offset calculation, the radio of power in the signal to power in the phase imbalance is μ and 1/μ iterations are needed to converge. As a result of the above process, α n =μY in Y qn +α n−1  (EQ 18) is used by the information signal generator  266  to generate an information signal  268  comprising Quadrature/Phase imbalance distortion adjust information for the Quadrature imbalance adjusters  220  in the QMod compensation datapath  210 . 
     With respect to Scaling imbalance distortions, the Scaling filter  264  performs the following calculation 
     
       
         
           
             
               
                 argmin 
                 β 
               
                
               
                   
               
                
               
                 VAR 
                  
                 
                   [ 
                   
                      
                     
                       ( 
                       
                         Y 
                         ^ 
                       
                       ) 
                     
                   
                   ] 
                 
               
             
             - 
             
               VAR 
                
               
                 [ 
                 
                    
                   
                     ( 
                     
                       Y 
                       ^ 
                     
                     ) 
                   
                 
                 ] 
               
             
           
         
       
     
     so that adjustment information can be sent to the Scaling adjuster  222  in the QMod compensation datapath  210  to eliminate/reduce Scaling imbalance distortions within the transmit data signal  235 . R and I are the real and imaginary operators. β is set as the scaling correction coefficient and an estimate of the corrected signal is defined as Ŷ= (Y)+jβ (Y)=Y i +jY q  (EQ 19). Since the minimum should again be 0, 0==E[Y i   2 ]−βE[Y q   2 ] (EQ 20). Solving for β results in 
     
       
         
           
             
               
                 
                   
                     β 
                     = 
                     
                       
                         E 
                          
                         
                           [ 
                           
                             Y 
                             i 
                             2 
                           
                           ] 
                         
                       
                       
                         E 
                          
                         
                           [ 
                           
                             Y 
                             q 
                             2 
                           
                           ] 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   
                     EQ 
                      
                     
                         
                     
                      
                     21 
                   
                   ) 
                 
               
             
           
         
       
     
     v (EQ 22), and 
     
       
         
           
             
               
                 
                   
                     log 
                      
                     
                         
                     
                      
                     
                       β 
                       n 
                     
                   
                   = 
                   
                     
                       log 
                        
                       
                         1 
                         n 
                       
                        
                       
                         
                           ∑ 
                           
                             r 
                             = 
                             0 
                           
                           n 
                         
                          
                         
                           Y 
                           ir 
                           2 
                         
                       
                     
                     - 
                     
                       log 
                        
                       
                         1 
                         n 
                       
                        
                       
                         
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                             r 
                             = 
                             0 
                           
                           n 
                         
                          
                         
                           
                             Y 
                             qr 
                             2 
                           
                           . 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                      
                     
                         
                     
                      
                     23 
                   
                   ) 
                 
               
             
           
         
       
     
     Because the Qmod controller  254  performs an iterative process, the first derivatives are to be equal and the extrema are to fall at the dame locations. In this case, the following substitutions are true and useful. First log x→x is consistent for 0&lt;x&lt;∞. Secondly, log x→|x| for all. In both cases for positive x the first derivative is positive, and for negative x the first derivative is negative. In the second case, both functions have one minimum at x=0. Thus, 
     
       
         
           
             
               
                 
                   
                     
                       β 
                       n 
                     
                     = 
                     
                       
                         
                           1 
                           n 
                         
                          
                         
                           
                             ∑ 
                             
                               r 
                               = 
                               0 
                             
                             n 
                           
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                               Y 
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                              
                           
                         
                       
                       - 
                       
                         
                           1 
                           n 
                         
                          
                         
                           
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                             n 
                           
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                               Y 
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                              
                           
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   and 
                 
               
               
                 
                   ( 
                   
                     EQ 
                      
                     
                         
                     
                      
                     24 
                   
                   ) 
                 
               
             
             
               
                 
                   
                     β 
                     n 
                   
                   = 
                   
                     
                       1 
                       n 
                     
                      
                     
                       
                         ∑ 
                         
                           r 
                           = 
                           0 
                         
                         n 
                       
                        
                       
                         
                           ( 
                           
                             
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                                
                             
                             - 
                             
                                
                               
                                 Y 
                                 qr 
                               
                                
                             
                           
                           ) 
                         
                         . 
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                      
                     
                         
                     
                      
                     25 
                   
                   ) 
                 
               
             
           
         
       
     
     Substituting n−1 for n results in 
     
       
         
           
             
               
                 
                   
                     β 
                     
                       n 
                       - 
                       1 
                     
                   
                   = 
                   
                     
                       1 
                       
                         n 
                         - 
                         1 
                       
                     
                      
                     
                       
                         ∑ 
                         
                           r 
                           = 
                           0 
                         
                         
                           n 
                           - 
                           1 
                         
                       
                        
                       
                         
                           ( 
                           
                             
                                
                               
                                 Y 
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                                
                             
                             - 
                             
                                
                               
                                 Y 
                                 qr 
                               
                                
                             
                           
                           ) 
                         
                         . 
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                      
                     
                         
                     
                      
                     26 
                   
                   ) 
                 
               
             
           
         
       
     
     Removing a term results in 
     
       
         
           
             
               
                 
                   
                     β 
                     n 
                   
                   = 
                   
                     
                       
                         1 
                         n 
                       
                        
                       
                         ( 
                         
                           
                              
                             
                               Y 
                               
                                 i 
                                  
                                 
                                     
                                 
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                                 n 
                               
                             
                              
                           
                           - 
                           
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                               Y 
                               qn 
                             
                              
                           
                         
                         ) 
                       
                     
                     + 
                     
                       
                         1 
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                        
                       
                         
                           ∑ 
                           
                             r 
                             = 
                             0 
                           
                           n 
                         
                          
                         
                           
                             ( 
                             
                               
                                  
                                 
                                   Y 
                                   ir 
                                 
                                  
                               
                               - 
                               
                                  
                                 
                                   Y 
                                   qr 
                                 
                                  
                               
                             
                             ) 
                           
                           . 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                      
                     
                         
                     
                      
                     27 
                   
                   ) 
                 
               
             
           
         
       
     
     Substituting back in yields 
     
       
         
           
             
               
                 
                   
                     β 
                     n 
                   
                   = 
                   
                     
                       
                         1 
                         n 
                       
                        
                       
                         ( 
                         
                           
                              
                             
                               Y 
                               
                                 i 
                                  
                                 
                                     
                                 
                                  
                                 n 
                               
                             
                              
                           
                           - 
                           
                              
                             
                               Y 
                               qn 
                             
                              
                           
                         
                         ) 
                       
                     
                     + 
                     
                       
                         
                           n 
                           - 
                           1 
                         
                         n 
                       
                        
                       
                         β 
                         
                           n 
                           - 
                           1 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                      
                     
                         
                     
                      
                     28 
                   
                   ) 
                 
               
             
           
         
       
     
     and β n =μ(|Y in |−|Y qn |)+β n−1  (EQ 29). As a result of the above process, EQ 29 is used by the information signal generator  266  to generate an information signal  268  comprising Scaling imbalance distortion adjust information for the Scaling imbalance adjusters  222  in the QMod compensation datapath  210 . 
     Therefore, as a result of the above process performed by the filters  258 ,  260 ,  262 ,  264  the information signal generator  266  receives a DC correction factor c (See EQ 7 above), a Quadrature imbalance correction factor α (See EQ 18 above), and a Scaling imbalance correction coefficient β (See EQ 29 above). The information signal generator  266  generates an information signal  268  that comprises this distortion adjustment information and transmits the information signal  268  to the QMod compensation datapath  210 . Each adjuster  216 ,  218 ,  220 ,  222  receives the appropriate adjust information and adjusts the baseband signal  202  such that the corresponding distortions added to the signal  202  by the QMod  224  are removed or reduced. In particular, the QMod compensation datapath  210  produces an output signal y=real(x)+j*(imag(x)*β+α*real(x))+c from the input signal  202 , where α and β are real valued numbers, y and x are a complex valued signal, and c is a complex number. 
     As can be seen from the above discussion, the various embodiments of the present invention advantageously manage non-linear and quadrature distortions in a continuous and autonomous way. For example, the distortion manager  110  continuously receives sampled data from a transmit data signal  235 , identifies the distortions within the transmit data signal  235 , generates signal adjustment information, and transmits this signal adjustment information to the non-linear and QMod compensation datapath  208 ,  210  so that signal corrections can be applied prior to the QMod  224  and power amplifier  214  inserting the distortions. Therefore, when the QMod  224  and power amplifier  214  insert their distortions, these distortions are reduced or eliminated. 
       FIGS. 3 to 4  are operational flow diagrams illustrating one example of a process of managing and optimizing non-linear and quadrature distortions within a transmit data signal. The operational flow diagram of  FIG. 3  begins at step  302 , and flows directly into step  304 . The transmitter  108 , at step  304 , generates, from a baseband data signal  202 , a transmit data signal  235  at an output of a transmitter amplifier  214 . A receiver circuit  238 , at step  306 , receives the transmit data signal  235 . The receiver circuit  238 , at step  308 , samples the transmit data signal  235 . The receiver circuit  238 , at step  310 , outputs a digital representation of the transmit data signal to a non-linear adaptation module  248  and a QMod controller  254 . The non-linear adaptation module  248 , at step  312 , determines the relative phase between the transmitter and receiver portions of the transmitter system  108  from the digital representation of the transmit data signal. The non-linear adaptation module  248 , at step  314 , then transmits the relative phase information to the QMod controller  254 . 
     The non-linear adaptation module  248 , at step  316 , analyzes the digital representation of the transmit data signal to identify representations of non-linear distortions. The non-linear adaptation module  248 , at step  318 , generates an information signal  252  comprising distortion adjustment information that is based on the representations of the non-linear distortions that have been identified. The non-linear adaptation module  248 , at step  320 , transmits the information signal to the non-linear datapath  208 . The non-linear datapath  208 , at step  322 , adjusts the transmit data signal  235  based on the distortion adjustment information received from the non-linear adaptation module  248  to reduce or eliminate the non-linear distortions within the transmit data signal  235 . The control then flows to entry point A of  FIG. 4   
     The QMod controller  254 , at step  402 , programs a phase shifter  256  with the relative phase information received from the non-linear adaptation module  248 . The QMod controller  254 , at step  404 , statistically analyzes the digital representation of the transmit data signal to identify representations of quadrature distortions. The QMod controller  254 , at step  406 , generates an information signal comprising distortion adjustment information based on the representations of quadrature distortions that have been identified. The QMod controller  254 , at step  408 , then transmits an information signal  268  to a quadrature compensation datapath  210 . The quadrature compensation datapath  210 , at step  410 , adjusts the transmit data signal  235  based on the distortion adjustment information received from the QMod controller  254  to reduce or eliminate the quadrature distortions within the transmit data signal  235 . The control then returns to step  306  of  FIG. 3  where the above processes are continuously and automatically repeated. 
     Referring now to  FIG. 5 , a more detailed view of a wireless device  500  is shown such as a wireless communication device  102 ,  104  or a base station  112 . It is assumed that the reader is familiar with wireless devices. To simplify the present description, only that portion of a wireless device that is relevant to the present invention is discussed. The wireless device  500  shown in  FIG. 5  operates under the control of a device controller/processor  502  that controls the sending and receiving of wireless communication signals and also performs the process discussed above with respect to  FIG. 5 . In receive mode, the device controller  502  electrically couples an antenna  504  through a transmit/receive switch  505  to at least one receiver  508 . The receiver  508  decodes the received signals and provides those decoded signals to the device controller  502 . 
     In transmit mode, the device controller  502  electrically couples the antenna  504 , through the transmit/receive switch  505 , to a one or more transmitters  510 , which include a distortion manager  110 . The distortion manager  110  has already been discussed above, and therefore, for the sake of brevity, will not be discussed in great detail here. The transmitter  510  is configured similar to the transmitter system  108  of  FIG. 2  and also for the sake of brevity, will not be discussed in great detail here. 
     The transmit/receive switch  506 , can include a diplexor/duplexor circuit for coupling transmitted signals from the transmitter(s)  510  to the antenna  504  and received signals from the antenna  504  to the receiver(s)  508 . It should be noted that in one embodiment, the at least one receiver  508  and the transmitter  510  comprise dual mode receivers and dual mode transmitters for receiving/transmitting over various access networks providing different air interface types. The wireless device  500  also includes a memory  512  and non-volatile storage  514 . The memory  512  and/or non-volatile storage  514  can include instructions, and store parameters, to perform the distortion management and optimization process discussed above with reference to  FIGS. 3 and 4 . 
     Although specific embodiments of the invention have been disclosed, those having ordinary skill in the art will understand that changes can be made to the specific embodiments without departing from the spirit and scope of the invention. The scope of the invention is not to be restricted, therefore, to the specific embodiments, and it is intended that the appended claims cover any and all such applications, modifications, and embodiments within the scope of the present invention.