Abstract:
A method for compensating mismatches of an in-phase signal and a quadrature signal of a transmitter/receiver is provided. The method includes: receiving a plurality of test signals to generate two groups of factors, respectively, where each group of factors is applied to two multipliers utilized for compensating a gain mismatch and a phase mismatch of the in-phase signal and the quadrature signal of the transmitter/receiver; then calculating a delay mismatch of the in-phase signal and the quadrature signal according to the two groups of factors.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a method for compensating a mismatch of an in-phase signal and a quadrature signal of a receiver or a transmitter, and more particularly, to a method for compensating gain mismatch/phase mismatch/path delay mismatch of an in-phase signal and a quadrature signal of a receiver or a transmitter. 
         [0003]    2. Description of the Prior Art 
         [0004]    In a conventional zero-IF (zero intermediate frequency) receiver, a radio frequency signal can be directly converted into a baseband signal. Because there is no middle frequency required to be selected, the image frequency interference of a super-heterodyne receiver will not be happened in the zero-IF receiver, and the zero-IF receiver does not need a high quality filter. In addition, because the zero-IF receiver includes only one local oscillator (i.e. only one phase noise source), the zero-IF receiver does not need large and expensive filter, and can be simply integrated. However, in the zero-IF receiver, the in-phase signal and the quadrature signal may have I/Q mismatch issue because the oscillation signals supplied to the in-phase channel and the quadrature channel are not matched. In addition, because the path delays of the in-phase channel and the quadrature channel may be different, the in-phase signal and the quadrature signal may also have the path delay mismatch issue. 
         [0005]    Because the gain mismatch/phase mismatch/path delay mismatch of the in-phase signal and the quadrature signal may influence the following signal processing operation (e.g., the bit error rate (BER) increases), how to design a method for estimating and compensating the gain mismatch/phase mismatch/path delay mismatch of the in-phase signal and the quadrature signal is an important topic. 
       SUMMARY OF THE INVENTION 
       [0006]    It is therefore an objective of the present invention to provide a method for compensating gain mismatch/phase mismatch/path delay mismatch of an in-phase signal and a quadrature signal of a receiver or a transmitter, to solve the above-mentioned problem. 
         [0007]    According to one embodiment of the present invention, a method for compensating a mismatch of an in-phase signal and a quadrature signal of a receiver is disclosed, where the receiver comprises a first channel, a second channel and a second multiplier, where the first channel comprises: a first mixer, for mixing a received signal with a first local oscillation signal to generate a first signal; a first multiplier, coupled to the first mixer, for generating an adjusted first signal according to the first signal; and an adder, coupled to the first multiplier; the second channel comprises: a second mixer, for mixing the received signal with a second local oscillation signal to generate a second signal; and an adjustable delay unit, coupled to the second mixer, for delaying the second signal to generate a delayed second signal; and the second multiplier is coupled between the adjustable delay unit and the adder, and is used for generating an adjusted second signal according to the delayed second signal, where the adder adds the adjusted first signal and the adjusted second signal to generate a compensated first signal; the compensated first signal is one of the in-phase signal and the quadrature signal, and the delayed second signal is the other one of the in-phase signal and the quadrature signal; and the method comprises: disabling the adjustable delay unit; receiving a first test signal to serve as the received signal to determine a first group of factors of the first multiplier and the second multiplier; receiving a second test signal to serve as the received signal to determine a second group of factors of the first multiplier and the second multiplier; and calculating a delay amount of the adjustable delay unit according to the first group of factors and the second group of factors. 
         [0008]    According to another embodiment of the present invention, a method for compensating a mismatch of an in-phase signal and a quadrature signal of a receiver is disclosed, where the receiver comprises a first channel, a second channel and a second multiplier, where the first channel comprises: a first mixer, for mixing a received signal with a first local oscillation signal to generate a first signal; an adjustable delay unit, coupled to the first mixer, for delaying the first signal to generate a delayed first signal; a first multiplier, coupled to the adjustable delay unit, for generating an adjusted first signal according to the delayed first signal; and an adder, coupled to the first multiplier; the second channel comprises: a second mixer, for mixing the received signal with a second local oscillation signal to generate a second signal; and the second multiplier is coupled between the second mixer and the adder, and is used for generating an adjusted second signal according to the second signal, wherein the adder adds the adjusted first signal and the adjusted second signal to generate a compensated first signal; where the compensated first signal is one of the in-phase signal and the quadrature signal, and the second signal is the other one of the in-phase signal and the quadrature signal; and the method comprises: disabling the adjustable delay unit; receiving a first test signal to serve as the received signal to determine a first group of factors of the first multiplier and the second multiplier; receiving a second test signal to serve as the received signal to determine a second group of factors of the first multiplier and the second multiplier; and calculating a delay amount of the adjustable delay unit according to the first group of factors and the second group of factors. 
         [0009]    According to another embodiment of the present invention, a method for compensating a mismatch of an in-phase signal and a quadrature signal of a transmitter is disclosed, wherein the transmitter comprises a first channel, a second multiplier and a second channel, where the first channel, comprises: a first multiplier, for receiving a first signal to generate a first adjusted first signal; and a first mixer, coupled to the first multiplier, for mixing the adjusted first signal with a first local oscillation signal to generate a mixed first signal; the second multiplier is for receiving the first signal to generate a second adjusted first signal; the second channel comprises: an adder, coupled to the second multiplier, for adding the second adjusted first signal and a second signal to generate an adjusted second signal; an adjustable delay unit, coupled to the adder, for delaying the adjusted second signal to generate a delayed second signal; and a second mixer, coupled to the adjustable delay unit, for mixing the delayed second signal with a second local oscillation signal to generate a mixed second signal; where the first adjusted first signal is one of the in-phase signal and the quadrature signal, and the delayed second signal is the other one of the in-phase signal and the quadrature signal; and the method comprises: disabling the adjustable delay unit; transmitting a first test signal and a second test signal to serve as the first signal and the second signal, respectively, to determine a first group of factors of the first multiplier and the second multiplier; transmitting a third test signal and a fourth test signal to serve as the first signal and the second signal, respectively, to determine a second group of factors of the first multiplier and the second multiplier; and calculating a delay amount of the adjustable delay unit according to the first group of factors and the second group of factors. 
         [0010]    According to another embodiment of the present invention, a method for compensating a mismatch of an in-phase signal and a quadrature signal of a transmitter is disclosed, where the transmitter comprises first channel, a second multiplier and a second channel, where the first channel comprises: a first multiplier, for receiving a first signal to generate a first adjusted first signal; an adjustable delay unit, coupled to the first multiplier, for delaying the first adjusted first signal to generate a delayed first signal; and a first mixer, coupled to the adjustable delay unit, for mixing the delayed first signal with a first local oscillation signal to generate a mixed first signal; the second multiplier is for receiving the first signal to generate a second adjusted first signal; the second channel comprises: an adder, coupled to the second multiplier, for adding the second adjusted first signal and a second signal to generate an adjusted second signal; and a second mixer, coupled to the adjustable delay unit, for mixing the adjusted second signal with a second local oscillation signal to generate a mixed second signal; where the delayed first signal is one of the in-phase signal and the quadrature signal, and the adjusted second signal is the other one of the in-phase signal and the quadrature signal; and the method comprises: disabling the adjustable delay unit; transmitting a first test signal and a second test signal to serve as the first signal and the second signal, respectively, to determine a first group of factors of the first multiplier and the second multiplier; transmitting a third test signal and a fourth test signal to serve as the first signal and the second signal, respectively, to determine a second group of factors of the first multiplier and the second multiplier; and calculating a delay amount of the adjustable delay unit according to the first group of factors and the second group of factors. 
         [0011]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a diagram illustrating a gain mismatch/phase mismatch/path delay mismatch of an in-phase signal and a quadrature signal of a prior art receiver. 
           [0013]      FIG. 2  is a diagram illustrating a diagram illustrating a receiver according to one embodiment of the present invention. 
           [0014]      FIG. 3  is a flowchart of a method for compensating a mismatch of the in-phase signal and the quadrature signal of the receiver according to one embodiment of the present invention. 
           [0015]      FIG. 4  is a diagram illustrating a diagram illustrating a receiver according to another embodiment of the present invention. 
           [0016]      FIG. 5  is a diagram illustrating a gain mismatch/phase mismatch/path delay mismatch of an in-phase signal and a quadrature signal of a prior art transmitter. 
           [0017]      FIG. 6  is a diagram illustrating a diagram illustrating a transmitter according to one embodiment of the present invention. 
           [0018]      FIG. 7  is a flowchart of a method for compensating a mismatch of the in-phase signal and the quadrature signal of the transmitter according to one embodiment of the present invention 
           [0019]      FIG. 8  is a diagram illustrating a diagram illustrating a transmitter according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ” The terms “couple” and “couples” are intended to mean either an indirect or a direct electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections. 
         [0021]    Please refer to  FIG. 1 , which is a diagram illustrating a gain mismatch/phase mismatch/path delay mismatch of an in-phase signal and a quadrature signal of a prior art receiver  100 , where the receiver  100  includes two mixers  110  and  120 ; and a path delay  130  shown in  FIG. 1  is used to represent a delay difference between an in-phase channel and a quadrature channel, and is not a circuit element. As shown in  FIG. 1 , the receiver  100  receives a signal that is represented as cos((w LO +w m )*t), and the signal passes through the mixers  110  and  120  and the path delay  130  to generate the in-phase signal I and the quadrature signal Q, respectively, where the in-phase signal I can be represented as (1+G)cos(w m t−P), and the quadrature signal Q can be represented as sin(w m (t−dt)), where “G” is a value of I/Q gain mismatch, “P” is a value of I/Q phase mismatch, the “dt” is a value of I/Q path delay mismatch, and the “G” value and the “P” value are generated due to the mismatch of two local oscillation signals generated from a local oscillator and supplied to the mixers  110  and  120 . 
         [0022]    Therefore, the objective of the present invention is to provide a receiver whose in-phase signal I and quadrature signal Q are close to their ideal values, that is cos(w m t) and sin(w m t), respectively. 
         [0023]    Please refer to  FIG. 2 , which is a diagram illustrating a diagram illustrating a receiver  200  according to one embodiment of the present invention. As shown in  FIG. 2 , the receiver  200  includes a first channel  210 , a second channel  220  and a multiplier  230 , where the first channel  210  includes a mixer  212 , a multiplier  214  and an adder  216 , and the second channel  220  includes a mixer  222  and an adjustable delay unit  224 . In addition, the receiver  200  further includes a control unit (not shown) that is used to generate control signals according to outputs of the first channel  210  and the second channel  220 , and the control unit uses the control signals to adjust a factor X of the multiplier  214 , a factor Y of the multiplier  230  and a delay amount of the adjustable delay unit  224 . In addition, in this embodiment, the receiver  200  is a zero-IF receiver, but it is not meant to be a limitation of the present invention. 
         [0024]    In the operations of the receiver  200 , the mixer  212  mixes a received signal Vin with a local oscillation signal OS 1  to generate an in-phase signal I, the multiplier  214  multiplies the in-phase signal I by the factor X to generate an adjusted in-phase signal Iadj. In addition, the mixer  222  mixes the received signal Vin with a local oscillation signal  052  to generate a quadrature signal Q, and the adjustable delay unit  224  delays the quadrature signal Q to generate a delayed quadrature signal Qmatch. Then, the multiplier  230  multiplies the delayed quadrature signal Qmatch by the factor Y to generate an adjusted quadrature signal Qadj. Finally, the adder  216  adds the adjusted in-phase signal Iadj and the adjusted quadrature signal Qadj to generate a compensated in-phase signal Imatch. 
         [0025]    Please refer to  FIG. 2  and  FIG. 3  together,  FIG. 3  is a flowchart of a method for compensating a mismatch of the in-phase signal I and the quadrature signal Q of the receiver  200  according to one embodiment of the present invention. Referring to  FIG. 3 , the flow is described as follows. 
         [0026]    In Step  300 , the adjustable delay unit  224  is disabled, that is the delay amount of the adjustable delay unit  224  is set to be 0. In Step  302 , the receiver  200  receives a first test signal, where the first test signal is a single tone signal having a frequency f 1 . Then, the control unit (not shown) adjusts the factor X of the multiplier  214  and the factor Y of the multiplier  230  by referring to an image rejection ratio (IRR) calculated by using the compensated in-phase signal Imatch and the delayed quadrature signal Qmatch to obtain a first group of factors (X 1 , Y 1 ), where when using the first group of factors (X 1 , Y 1 ) the receiver  200  has the optimal IRR. Referring to  FIG. 1  and  FIG. 2 , assuming that the outputs of the mixers  212  and  222  are (1+G)cos(w m t−P) and sin(w m (t−dt)), respectively, shown in  FIG. 1 , the value of Y 1  should be close to (−tan(P+2πf 1 *dt)) when the compensated in-phase signal Imatch and the delayed quadrature signal Qmatch have the optimal IRR. 
         [0027]    In Step  304 , the receiver  200  receives a second test signal, where the second test signal is a single tone signal having a frequency f 2 . Then, the control unit (not shown) adjusts the factor X of the multiplier  214  and the factor Y of the multiplier  230  by referring to the IRR calculated by using the compensated in-phase signal Imatch and the delayed quadrature signal Qmatch to obtain a second group of factors (X 2 , Y 2 ), where when using the second group of factors (X 2 , Y 2 ) the receiver  200  has the optimal IRR. Referring to  FIG. 1  and  FIG. 2 , assuming that the outputs of the mixers  212  and  222  are (1+G)cos(w m t−P) and sin(w m (t−dt)), respectively, shown in  FIG. 1 , the value of Y 2  should be close to (−tan(P+2πf 2 *dt)) when the compensated in-phase signal Imatch and the delayed quadrature signal Qmatch have the optimal IRR. 
         [0028]    In Step  306 , the control unit uses the first group of factors (X 1 , Y 1 ) and the second group of factors (X 2 , Y 2 ) to calculate a delay amount of the adjustable delay unit  224 . In detail, because in Steps  302  and  304  it is calculated that: Y 1 ≈(−tan(P+2πf 1 *dt)) and Y 2 ≈(−tan(P+2πf 2 *dt)), the delay amount dt between the in-phase signal I and the quadrature signal Q can be calculated by using the following formula: 
         [0000]        dt ≈( Y 1 −Y 2)/(2π( f 2 −f 1)).
 
         [0029]    In addition, because dt=Δ*Ts=Δ/Fs, where Ts and Fs are a sampling clock period and a sampling clock frequency of an analog-to-digital converter (ADC) of the receiver  200 , respectively, a delay parameter Δ used by the adjustable delay unit  224  can be calculated as follows: 
         [0000]    
       
         
           
             
               Δ 
               = 
               
                 
                   
                     ( 
                     
                       
                         Y 
                          
                         
                             
                         
                          
                         1 
                       
                       - 
                       
                         Y 
                          
                         
                             
                         
                          
                         2 
                       
                     
                     ) 
                   
                   
                     
                       2 
                        
                       
                         π 
                          
                         
                           ( 
                           
                             
                               f 
                                
                               
                                   
                               
                                
                               2 
                             
                             - 
                             
                               f 
                                
                               
                                   
                               
                                
                               1 
                             
                           
                           ) 
                         
                       
                     
                     Fs 
                   
                 
                 = 
                 
                   
                     ( 
                     
                       
                         Y 
                          
                         
                             
                         
                          
                         1 
                       
                       - 
                       
                         Y 
                          
                         
                             
                         
                          
                         2 
                       
                     
                     ) 
                   
                   
                     
                       2 
                        
                       
                         π 
                          
                         
                           ( 
                           
                             
                               tone_idx 
                                
                               
                                 ( 
                                 
                                   f 
                                    
                                   
                                       
                                   
                                    
                                   2 
                                 
                                 ) 
                               
                             
                             - 
                             
                               tone_idx 
                                
                               
                                 ( 
                                 
                                   f 
                                    
                                   
                                       
                                   
                                    
                                   1 
                                 
                                 ) 
                               
                             
                           
                           ) 
                         
                       
                     
                     FFT_pts 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    where FFT_pts is a number of points used when performing a fast Fourier Transform upon the first test signal and the second test signal, and tone_index is an index of the tone/frequency. 
         [0030]    In Step  308 , the control unit (not shown) enables the adjustable delay unit  224  and sets adjustable delay unit  224  according to the delay parameter Δ or the delay amount dt. 
         [0031]    In Step  310 , the receiver  200  receives a third test signal, where the third test signal is a single tone signal having a frequency f 3 . Then, the control unit (not shown) adjusts the factor X of the multiplier  214  and the factor Y of the multiplier  230  by referring to the IRR calculated by using the compensated in-phase signal Imatch and the delayed quadrature signal Qmatch to obtain a third group of factors (X 3 , Y 3 ), where when using the third group of factors (X 3 , Y 3 ) the receiver  200  has the optimal IRR. The third group of factors (X 3 , Y 3 ) are used by the multipliers  214  and  230  of the receiver  200  in the following operations. 
         [0032]    In light of above, after the delay parameter Δ used in adjustable delay unit  224 , the factor X 3  of the multiplier  214  and the factor Y 3  of the multiplier  230  are determined, the receiver  200  can eliminate the gain mismatch/phase mismatch/path delay mismatch of the in-phase signal I and the quadrature signal Q, and the gain/phase/path delay of the compensated in-phase signal Imatch and the delayed quadrature signal Qmatch are matched. In particular, when eliminating the path delay mismatch of the in-phase signal I and the quadrature signal Q, the receiver  200  can simultaneously eliminate the frequency-dependent phase mismatch and the frequency-independent phase mismatch. 
         [0033]    It is noted that, in the embodiment shown in  FIG. 2 , the first channel  210  is the in-phase channel and the second channel  220  is the quadrature channel. In other embodiments, however, the first channel  210  can be the quadrature channel and the second channel  220  can be the in-phase channel, and the determination steps of the delay parameter Δ, the factor X 3  of the multiplier  214  and the factor Y 3  of the multiplier  230  are similar to the steps shown in  FIG. 3  (only the formula for calculating the delay parameter Δ is different from the formula described in step  306 ). Because a person skilled in this art should understand how to derive the formula to obtain the delay parameter Δ and the two factors X 3  and Y 3  after reading the above-mentioned disclosure, further descriptions are omitted here. 
         [0034]    Please refer to  FIG. 4 , which is a diagram illustrating a receiver  400  according to another embodiment of the present invention. As shown in  FIG. 4 , the receiver  400  includes a first channel  410 , a second channel  420  and a multiplier  430 , where the first channel  410  includes a mixer  412 , an adjustable delay unit  414 , a multiplier  416  and an adder  418 , and the second channel  420  includes a mixer  422 . In addition, the receiver  400  further includes a control unit (not shown) that is used to generate control signals according to outputs of the first channel  410  and the second channel  420 , and the control unit uses the control signals to adjust a factor X of the multiplier  416 , a factor Y of the multiplier  430  and a delay amount of the adjustable delay unit  414 . 
         [0035]    In the operations of the receiver  400 , the mixer  412  mixes a received signal Vin with a local oscillation signal OS 1  to generate an in-phase signal I, the adjustable delay unit  414  delays the in-phase signal I to generate a delayed in-phase signal Id, and the multiplier  416  multiplies the delayed in-phase signal Id by the factor X to obtain an adjusted in-phase signal Iadj. In addition, the mixer  422  mixes the received signal Vin with a local oscillation signal  052  to generate a quadrature signal Q, the multiplier  430  multiplies the quadrature signal Q by the factor Y to obtain an adjusted quadrature signal Qadj. Finally, the adder  418  adds the adjusted in-phase signal Iadj and the adjusted quadrature signal Qadj to generate a compensated in-phase signal Imatch. 
         [0036]    The method for determining the delay parameter of the adjustable delay unit  414 , the factor X of the multiplier  416  and the factor Y of the multiplier  430  are similar to the steps shown in  FIG. 3 , and only the formula for calculating the delay parameter of the adjustable delay unit  414  is different from the formula for calculating the delay parameter Δ of the adjustable delay unit  224  of the receiver  200  shown in  FIG. 2  (in Step  306 ). Because a person skilled in this art should understand the following calculations after reading the above-mentioned disclosure (e.g., the delay parameter of the adjustable delay unit  414  can be calculated by the formula: 
         [0000]    
       
         
           
             
               Δ 
               = 
               
                 
                   - 
                   
                     
                       ( 
                       
                         
                           Y 
                            
                           
                               
                           
                            
                           1 
                         
                         - 
                         
                           Y 
                            
                           
                               
                           
                            
                           2 
                         
                       
                       ) 
                     
                     
                       
                         2 
                          
                         
                           π 
                            
                           
                             ( 
                             
                               
                                 f 
                                  
                                 
                                     
                                 
                                  
                                 2 
                               
                               - 
                               
                                 f 
                                  
                                 
                                     
                                 
                                  
                                 1 
                               
                             
                             ) 
                           
                         
                       
                       Fs 
                     
                   
                 
                 = 
                 
                   - 
                   
                     
                       ( 
                       
                         
                           Y 
                            
                           
                               
                           
                            
                           1 
                         
                         - 
                         
                           Y 
                            
                           
                               
                           
                            
                           2 
                         
                       
                       ) 
                     
                     
                       
                         2 
                          
                         
                           π 
                            
                           
                             ( 
                             
                               
                                 tone_idx 
                                  
                                 
                                   ( 
                                   
                                     f 
                                      
                                     
                                         
                                     
                                      
                                     2 
                                   
                                   ) 
                                 
                               
                               - 
                               
                                 tone_idx 
                                  
                                 
                                   ( 
                                   
                                     f 
                                      
                                     
                                         
                                     
                                      
                                     1 
                                   
                                   ) 
                                 
                               
                             
                             ) 
                           
                         
                       
                       FFT_pts 
                     
                   
                 
               
             
             , 
           
         
       
     
         [0000]    that is a negative of the delay parameter described in the embodiment shown in  FIG. 2 ), further descriptions are omitted here. 
         [0037]    It is noted that, in the embodiment shown in  FIG. 4 , the first channel  410  is the in-phase channel and the second channel  420  is the quadrature channel. In other embodiments, however, the first channel  410  can be the quadrature channel and the second channel  420  can be the in-phase channel, and the determination steps of the delay parameter Δ, the factor X 3  of the multiplier  416  and the factor Y 3  of the multiplier  430  are similar to the steps shown in  FIG. 3  (only the formula for calculating the delay parameter Δ is different from the formula described in step  306 ). Because a person skilled in this art should understand how to derive the formula to obtain the delay parameter Δ and the two factors X 3  and Y 3  after reading the above-mentioned disclosure, further descriptions are omitted here. 
         [0038]    Please refer to  FIG. 5 , which is a diagram illustrating a gain mismatch/phase mismatch/path delay mismatch of an in-phase signal and a quadrature signal of a prior art transmitter  500 , where the transmitter  500  includes two mixers  510  and  520  and an adder  530 ; and a path delay  540  shown in  FIG. 5  is used to represent a delay difference between an in-phase channel and a quadrature channel, and is not a circuit element. As shown in  FIG. 5 , the transmitter  500  receives an in-phase signal I and a quadrature signal Q, and the in-phase signal I and a quadrature signal Q are processes by the mixers  510  and  520 , the path delay  540  and the adder  530  to generate an output signal Vout, and the output signal Vout is radiated by an antenna. The local oscillation signals supplied to the mixers  510  and  520  are (1+G)cos(w LO t+P) and −sin(w LO t), respectively, where “G” is a value of I/Q gain mismatch, “P” is a value of I/Q phase mismatch, the “dt” is a value of I/Q path delay mismatch. Because the in-phase signal and the quadrature signal included in the output signal Vout may have the gain mismatch/phase mismatch/path delay mismatch, errors may be happened when the output signal Vout is received and processed by a receiver. 
         [0039]    Please refer to  FIG. 6 , which is a diagram illustrating a transmitter  600  according to one embodiment of the present invention. As shown in  FIG. 6 , the transmitter  600  includes a first channel  610 , a second channel  620 , a multiplier  630  and an adder  640 , where the first channel  610  includes a mixer  612  and a multiplier  614 , and the second channel  620  includes a mixer  622 , an adjustable delay unit  624  and an adder  626 . In addition, the transmitter  600  further includes a control unit (not shown) that is used to generate control signals according to the output signal Vout of the transmitter  600 , and the control unit uses the control signals to adjust a factor X of the multiplier  614 , a factor Y of the multiplier  630  and a delay amount of the adjustable delay unit  624 . 
         [0040]    In the operations of the transmitter  600 , the multiplier  614  multiplies an in-phase signal I by the factor X to generate a first adjusted in-phase signal Iadj 1 , and the mixer  612  mixes the first adjusted in-phase signal Iadj 1  with a local oscillation signal OS 1  to generate a mixed in-phase signal Imix. At the same time, the multiplier  630  multiplies the in-phase signal I by the factor Y to generate a second adjusted in-phase signal Iadj 2 , the adder  626  adds the second adjusted in-phase signal Iadj 2  and a quadrature signal Q to generate an adjusted quadrature signal Dadj, the adjustable delay unit  624  delays the adjusted quadrature signal Dadj to generate a delayed quadrature signal Qd, and the mixer  622  mixes the delayed quadrature signal Qd with a local oscillation signal OS 2  to generate a mixer oscillation signal Qmix. Finally, the adder  640  adds the mixed in-phase signal Imix and the mixer oscillation signal Qmix to generate the output signal Vout. 
         [0041]    Please refer to  FIG. 6  and  FIG. 7  together,  FIG. 7  is a flowchart of a method for compensating a mismatch of the in-phase signal and the quadrature signal of the transmitter  600  according to one embodiment of the present invention. Referring to  FIG. 7 , the flow is described as follows. 
         [0042]    In Step  700 , the adjustable delay unit  624  is disabled, that is the delay amount of the adjustable delay unit  624  is set to be 0. Then, in Step  702 , the transmitter  600  transmits a first test signal and a second test signal, where the first test signal and the second test signal are the in-phase signal and quadrature signal, respectively, and each of them is a single tone signal having a frequency f 1  (i.e., the first test signal serves as the in-phase signal I shown in  FIG. 6 , and the second test signal serves as the quadrature signal Q shown in  FIG. 6 ). Then, the control unit (not shown) adjusts the factor X of the multiplier  614  and the factor Y of the multiplier  630  by referring to an image rejection ratio (IRR) calculated by using the output signal Vout to obtain a first group of factors (X 1 , Y 1 ), where when using the first group of factors (X 1 , Y 1 ) the transmitter  600  has the optimal IRR. Referring to  FIG. 5  and  FIG. 6 , assuming that the oscillation signals supplied to the mixers  612  and  622  are (1+G)cos(w LO t+P) and −sin(w LO t), respectively, the value of Y 1  should be close to (−tan(P+2πf 1 *dt)) when the output signal Vout has the optimal IRR. 
         [0043]    In Step  704 , the transmitter  600  transmits a third test signal and a fourth test signal, where the third test signal and the fourth test signal are the in-phase signal and quadrature signal, respectively, and each of them is a single tone signal having a frequency f 2  (i.e., the third test signal serves as the in-phase signal I shown in  FIG. 6 , and the fourth test signal serves as the quadrature signal Q shown in  FIG. 6 ). Then, the control unit (not shown) adjusts the factor X of the multiplier  614  and the factor Y of the multiplier  630  by referring to an image rejection ratio (IRR) calculated by using the output signal Vout to obtain a second group of factors (X 2 , Y 2 ), where when using the second group of factors (X 2 , Y 2 ) the transmitter  600  has the optimal IRR. Referring to  FIG. 5  and  FIG. 6 , assuming that the oscillation signals supplied to the mixers  612  and  622  are (1+G)cos(w LO t+P) and −sin(w LO t), respectively, the value of Y 2  should be close to (−tan(P+2πf 2 *dt)) when the output signal Vout has the optimal IRR. 
         [0044]    In Step  706 , the control unit uses the first group of factors (X 1 , Y 1 ) and the second group of factors (X 2 , Y 2 ) to calculate a delay amount of the adjustable delay unit  624 . In detail, because in Steps  702  and  704  it is calculated that: Y 1 ≈(−tan(P+2πf 1 *dt)) and Y 2 ≈(−tan(P+2πf 2 *dt)), the delay amount dt between the in-phase signal I and the quadrature signal Q can be calculated by using the following formula: 
         [0000]        dt ≈( Y 1 −Y 2)/(2π( f 2 −f 1)).
 
         [0045]    In addition, because dt=Δ*Ts=Δ/Fs, where Ts and Fs are a sampling clock period and a sampling clock frequency of an analog-to-digital converter (ADC) of the receiver  600 , respectively, a delay parameter Δ used by the adjustable delay unit  624  can be calculated as follows: 
         [0000]    
       
         
           
             
               Δ 
               = 
               
                 
                   
                     ( 
                     
                       
                         Y 
                          
                         
                             
                         
                          
                         1 
                       
                       - 
                       
                         Y 
                          
                         
                             
                         
                          
                         2 
                       
                     
                     ) 
                   
                   
                     
                       2 
                        
                       
                         π 
                          
                         
                           ( 
                           
                             
                               f 
                                
                               
                                   
                               
                                
                               2 
                             
                             - 
                             
                               f 
                                
                               
                                   
                               
                                
                               1 
                             
                           
                           ) 
                         
                       
                     
                     Fs 
                   
                 
                 = 
                 
                   
                     ( 
                     
                       
                         Y 
                          
                         
                             
                         
                          
                         1 
                       
                       - 
                       
                         Y 
                          
                         
                             
                         
                          
                         2 
                       
                     
                     ) 
                   
                   
                     
                       2 
                        
                       
                         π 
                          
                         
                           ( 
                           
                             
                               tone_idx 
                                
                               
                                 ( 
                                 
                                   f 
                                    
                                   
                                       
                                   
                                    
                                   2 
                                 
                                 ) 
                               
                             
                             - 
                             
                               tone_idx 
                                
                               
                                 ( 
                                 
                                   f 
                                    
                                   
                                       
                                   
                                    
                                   1 
                                 
                                 ) 
                               
                             
                           
                           ) 
                         
                       
                     
                     FFT_pts 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    where FFT_pts is a number of points used when performing a fast Fourier Transform upon the first test signal and the second test signal, and tone_index is an index of the tone/frequency. 
         [0046]    In Step  708 , the control unit (not shown) enables the adjustable delay unit  624  and sets adjustable delay unit  624  according to the delay parameter Δ or the delay amount dt. 
         [0047]    In Step  710 , the transmitter  600  transmits a fifth test signal and a sixth test signal, where the fifth test signal and the sixth test signal are the in-phase signal and quadrature signal, respectively, and each of them is a single tone signal having a frequency f 3  (i.e., the fifth test signal serves as the in-phase signal I shown in  FIG. 6 , and the sixth test signal serves as the quadrature signal Q shown in  FIG. 6 ). Then, the control unit (not shown) adjusts the factor X of the multiplier  614  and the factor Y of the multiplier  630  by referring to the IRR calculated by using the output signal Vout to obtain a third group of factors (X 3 , Y 3 ), where when using the third group of factors (X 3 , Y 3 ) the transmitter  600  has the optimal IRR. The third group of factors (X 3 , Y 3 ) are used by the multipliers  614  and  630  of the transmitter  600  in the following operations. 
         [0048]    In light of above, after the delay parameter Δ used in adjustable delay unit  624 , the factor X 3  of the multiplier  614  and the factor Y 3  of the multiplier  630  are determined, the transmitter  600  can eliminate the gain mismatch/phase mismatch/path delay mismatch of the in-phase signal I and the quadrature signal Q included in the output signal Vout. When the output signal Vout is received and demodulated by a receiver, the gain/phase/path delay of the generated in-phase signal and quadrature signal will be matched. 
         [0049]    It is noted that, in the embodiment shown in  FIG. 6 , the first channel  610  is the in-phase channel and the second channel  620  is the quadrature channel. In other embodiments, however, the first channel  610  can be the quadrature channel and the second channel  620  can be the in-phase channel, and the determination steps of the delay parameter Δ, the factor X 3  of the multiplier  614  and the factor Y 3  of the multiplier  630  are similar to the steps shown in  FIG. 7  (only the formula for calculating the delay parameter Δ is different from the formula described in step  706 ). Because a person skilled in this art should understand how to derive the formula to obtain the delay parameter Δ and the two factors X 3  and Y 3  after reading the above-mentioned disclosure, further descriptions are omitted here. 
         [0050]    Please refer to  FIG. 8 , which is a diagram illustrating a transmitter  800  according to another embodiment of the present invention. As shown in  FIG. 8 , the transmitter  800  includes a first channel  810 , a second channel  820 , a multiplier  830  and an adder  840 , where the first channel  810  includes a mixer  812 , an adjustable delay unit  814  and a multiplier  816 , and the second channel  820  includes a mixer  822  and an adder  824 . In addition, the transmitter  800  further includes a control unit (not shown) that is used to generate control signals according to the output signal Vout of the transmitter  800 , and the control unit uses the control signals to adjust a factor X of the multiplier  816 , a factor Y of the multiplier  830  and a delay amount of the adjustable delay unit  814 . 
         [0051]    In the operations of the transmitter  800 , the multiplier  816  multiplies an in-phase signal I by the factor X to generate a first adjusted in-phase signal Iadj 1 , the adjustable delay unit  814  delays the first adjusted in-phase signal Iadj 1  to generate a delayed in-phase signal Id, and the mixer  812  mixes the delayed in-phase signal Id with a local oscillation signal OS 1  to generate a mixed in-phase signal Imix. At the same time, the multiplier  830  multiplies the in-phase signal I by the factor Y to generate a second adjusted in-phase signal Iadj 2 , the adder  824  adds the second adjusted in-phase signal Iadj 2  and a quadrature signal Q to generate an adjusted quadrature signal Qadj, and the mixer  822  mixes the adjusted quadrature signal Qadj with a local oscillation signal  052  to generate a mixed quadrature signal Qmix. Finally, the adder  840  adds the mixed in-phase signal Imix and the mixed quadrature signal Qmix to generate an output signal Vout. 
         [0052]    The method for determining the delay parameter of the adjustable delay unit  814 , the factor X of the multiplier  816  and the factor Y of the multiplier  830  are similar to the steps shown in  FIG. 7 , and only the formula for calculating the delay parameter of the adjustable delay unit  814  is different from the formula for calculating the delay parameter Δ of the adjustable delay unit  624  of the transmitter  600  shown in  FIG. 6  (in Step  706 ). Because a person skilled in this art should understand the following calculations after reading the above-mentioned disclosure (e.g., the delay parameter of the adjustable delay unit  814  can be calculated by the formula: 
         [0000]    
       
         
           
             
               Δ 
               = 
               
                 
                   - 
                   
                     
                       ( 
                       
                         
                           Y 
                            
                           
                               
                           
                            
                           1 
                         
                         - 
                         
                           Y 
                            
                           
                               
                           
                            
                           2 
                         
                       
                       ) 
                     
                     
                       
                         2 
                          
                         
                           π 
                            
                           
                             ( 
                             
                               
                                 f 
                                  
                                 
                                     
                                 
                                  
                                 2 
                               
                               - 
                               
                                 f 
                                  
                                 
                                     
                                 
                                  
                                 1 
                               
                             
                             ) 
                           
                         
                       
                       Fs 
                     
                   
                 
                 = 
                 
                   - 
                   
                     
                       ( 
                       
                         
                           Y 
                            
                           
                               
                           
                            
                           1 
                         
                         - 
                         
                           Y 
                            
                           
                               
                           
                            
                           2 
                         
                       
                       ) 
                     
                     
                       
                         2 
                          
                         
                           π 
                            
                           
                             ( 
                             
                               
                                 tone_idx 
                                  
                                 
                                   ( 
                                   
                                     f 
                                      
                                     
                                         
                                     
                                      
                                     2 
                                   
                                   ) 
                                 
                               
                               - 
                               
                                 tone_idx 
                                  
                                 
                                   ( 
                                   
                                     f 
                                      
                                     
                                         
                                     
                                      
                                     1 
                                   
                                   ) 
                                 
                               
                             
                             ) 
                           
                         
                       
                       FFT_pts 
                     
                   
                 
               
             
             , 
           
         
       
     
         [0000]    that is a negative of the delay parameter described in the embodiment shown in  FIG. 6 ), further descriptions are omitted here. 
         [0053]    It is noted that, in the embodiment shown in  FIG. 8 , the first channel  810  is the in-phase channel and the second channel  820  is the quadrature channel. In other embodiments, however, the first channel  810  can be the quadrature channel and the second channel  820  can be the in-phase channel, and the determination steps of the delay parameter Δ, the factor X 3  of the multiplier  816  and the factor Y 3  of the multiplier  830  are similar to the steps shown in  FIG. 7  (only the formula for calculating the delay parameter Δ is different from the formula described in step  706 ). Because a person skilled in this art should understand how to derive the formula to obtain the delay parameter Δ and the two factors X 3  and Y 3  after reading the above-mentioned disclosure, further descriptions are omitted here. 
         [0054]    Briefly summarized, in the method for compensating gain mismatch/phase mismatch/path delay mismatch of an in-phase signal and a quadrature signal of a receiver or a transmitter of the present invention, parameters for compensating the gain mismatch/phase mismatch/path delay mismatch can be determined correctly and efficiently, and prevent errors in the following operations. 
         [0055]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.