Abstract:
The purpose of the present invention is to shorten a time required to perform Auto Gain Control (AGC) processing in a wireless device that can be applied to a plurality of wireless systems. On the basis of a first gain adjusted by means of a gain control unit ( 450 - 1 ), an initial gain setting unit ( 460 ) sets, for a variable gain unit ( 432 - 2 ), an initial gain (converted second initial gain) at the start of gain adjustment. Then, a gain control unit ( 450 - 2 ) sets the initial gain to a second gain at the time of starting the gain adjustment, and adjusts the second gain on the basis of IQ signals of a system, the IQ signals having the level adjusted by means of the variable gain unit ( 432 - 2 ).

Description:
TECHNICAL FIELD 
     The present invention relates to a wireless device capable of multiple wireless schemes, and a reception method. 
     BACKGROUND ART 
     As performance of recent wireless devices increases, wireless devices capable of multiple wireless schemes have emerged. This is partly because increased performance of high-frequency parts or the like has enabled high-frequency circuits to be partly shared by multiple different frequency systems and such systems may thereby be created with few additional components. Such multiple wireless schemes implemented in one wireless device are expected to cooperate to create new added value. For example, studies are in progress to create wireless devices capable of cellular communication such as W-CDMA (Wideband Code Division Multiple Access), and wireless LAN (Local Area Network) communication. Conventional wireless devices are adapted to the multiple wireless schemes by implementing independent processing sections corresponding to the multiple wireless schemes. The conventional wireless devices, for example, are provided with an independent processing section that performs synchronization processes such as AGC (Auto Gain Control), AFC (Auto Frequency Control), and timing synchronization during a preamble period, for each wireless scheme. 
     The wireless devices capable of the multiple wireless schemes, however, consume higher power due to the implementation of the independent processing section corresponding to each of the multiple wireless schemes. 
     PTL 1 discloses a technique for fast AFC process while maintaining low power consumption in a wireless device capable of multiple wireless schemes, in order to solve this problem. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1 
         Japanese Patent Application Laid-Open No. 2007-267304 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     Time required for the AGC process generally accounts for the largest percentage of time required for the respective synchronization processes in the preamble period. In addition, the AFC and establishment of the synchronization cannot be performed unless the AGC is completed. Accordingly, quick completion of the AGC process in the wireless device can increase time available for the AFC process, the timing synchronization process and the like, thereby improving overall communication performance. 
     A technique for reducing the time required for the AGC process in the conventional wireless devices capable of the multiple wireless schemes, however, has not been sufficiently studied. 
     An object of the present invention is to provide a wireless device that is capable of the multiple wireless schemes and can reduce the time required for the AGC process, and a reception method thereof. 
     Solution to Problem 
     To achieve the abovementioned object, a wireless device reflecting one aspect of the present invention includes a first antenna that receives a first signal modulated by a first wireless scheme; a second antenna that receives a second signal modulated by a second wireless scheme; a first variable gain section that adjusts a level of the first signal; a second variable gain section that adjusts a level of the second signal; a first gain control section that adjusts a first gain based on the first signal whose level has been adjusted by the first variable gain section, the first gain being a gain of the first variable gain section; a setting section that sets an initial gain based on the first signal, the initial gain being a second gain that is a gain of the second variable gain section, the initial gain being used by the second variable gain section at start of gain adjustment; and a second gain control section that sets the initial gain to the second gain at the start of the gain adjustment, and adjusts the second gain based on the second signal whose level has been adjusted by the second variable gain section. 
     To achieve the abovementioned object, a reception method reflecting one aspect of the present invention includes a first receiving step of receiving a first signal modulated by a first wireless scheme; a second receiving step of receiving a second signal modulated by a second wireless scheme; a first adjustment step of adjusting a level of the first signal; a second adjustment step of adjusting a level of the second signal; a first gain control step of adjusting a first gain based on the first signal whose level has been adjusted by the first adjustment step, the first gain being a gain in the first adjustment step; a setting step of setting an initial gain based on the first signal, the initial gain being a second gain that is a gain in the second adjustment step, the initial gain being used by the second adjustment step at start of gain adjustment; and a second gain control step of setting the initial gain to the second gain at the start of the gain adjustment, and adjusting the second gain based on the second signal whose level has been adjusted by the second adjustment step. 
     Advantageous Effects of Invention 
     According to the present invention, the wireless device capable of the multiple wireless schemes can reduce the time required for the AGC process. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration example of a wireless system according to Embodiment 1 of the present invention; 
         FIG. 2  is a block diagram illustrating the configuration of a wireless device according to Embodiment 1; 
         FIG. 3  is a diagram illustrating an example of the internal configuration of a gain control section in a reception processing section for an “A system” according to Embodiment 1; 
         FIG. 4  is a diagram illustrating an example of the internal configuration of a gain control section in a reception processing section for a “B system” according to Embodiment 1; 
         FIG. 5  is a flowchart illustrating an example of operations of the wireless device according to Embodiment 1; 
         FIG. 6  is a block diagram illustrating an example of the configuration of variable gain sections in the reception processing sections for the A and B systems according to Embodiment 1; 
         FIG. 7  is a block diagram illustrating an example of the configurations of the variable gain sections in the reception processing sections for the A and B systems according to Embodiment 1; 
         FIG. 8  is a diagram illustrating an example of a table stored in an initial gain setting section according to Embodiment 1; 
         FIG. 9  is a block diagram illustrating the configuration of the wireless device according to Embodiment 2 of the present invention; 
         FIG. 10  is a diagram illustrating an example of the internal configuration of the gain control section in the reception processing section for the “A system” according to Embodiment 2; 
         FIG. 11  is a diagram illustrating an example of the internal configuration of the gain control section in the reception processing section for the “B system” according to Embodiment 2; 
         FIG. 12  is a diagram illustrating a relationship among the differences P 1 , Q 1 , P 2 , Q 2 , P 3  and Q 3 ; 
         FIG. 13  is a diagram illustrating an example of the table stored in the initial gain setting section according to Embodiment 2; and 
         FIG. 14  is a diagram illustrating another example of the table stored in the initial gain setting section according to Embodiment 2. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described in detail below with reference to the drawings. 
     (Embodiment 1) 
       FIG. 1  is a diagram illustrating a configuration example of a wireless system according to Embodiment 1 of the present invention. Wireless system  100  of  FIG. 1  includes wireless device # 1   200  and wireless device # 2   300 . The case will be described below where wireless device # 1   200  and wireless device # 2   300  are capable of two wireless communication systems, an “A system” and a “B system,” by way of example. The two wireless systems, for example, correspond to different wireless standards like a cellular communication system such as W-CDMA, and a wireless LAN communication system. 
     Wireless device # 1   200  includes processing section for the “A system”  210  and processing section for the “B system”  220 . Wireless device # 2   300  includes processing section for the “A system”  310  and processing section for the “B system”  320 . 
     Processing sections  210  and  310  for the “A system” perform transmission and reception processes for the “A system”. Processing sections  220  and  320  for the “B system” perform transmission and reception processes for the “B system”. 
     The case will be described below where wireless device # 1   200  receives signals of the A and B systems that are transmitted from wireless device # 2   300 . Communication of the “B system” may or may not be performed simultaneously with communication of the “A system”. Hereinafter, the communication of the “A system” is assumed to have been performed prior to the communication of the “B system”. 
     Wireless device # 1   200  knows in advance that it receives the signal transmitted from wireless device # 2   300 , next in the communication of the “B system”. Wireless device # 1   200  has obtained this information through previous arrangements made between wireless device # 1   200  and wireless device # 2   300 , statistics of past communication, or information shared among members in the communication. 
       FIG. 2  is a block diagram illustrating the configuration of the wireless device according to the present embodiment. Wireless device  400  of  FIG. 2  is applied to wireless device # 1  ( 200 ) of  FIG. 1 . In order to avoid complicated descriptions,  FIG. 2  illustrates only components associated with the reception of the signals of the A and B systems, which is closely related to the present invention.  FIG. 2  omits illustrations and descriptions of components associated with the transmission of the signals of the A and B systems. 
     Wireless device  400  includes antennas  410 - 1  and  410 - 2 , reception processing section  420 - 1  for the “A system”, reception processing section  420 - 2  for the “B system,” and initial gain setting section  460 . 
     Antenna  410 - 1  receives the signal of the “A system”. 
     Antenna  410 - 2  receives the signal of the “B system”. 
     Reception processing section for the “A system”  420 - 1  includes high-frequency circuit  430 - 1 , demodulation section  440 - 1  and gain control section  450 - 1 . 
     High-frequency circuit  430 - 1  includes orthogonal demodulation section  431 - 1 , variable gain section  432 - 1  and AD (Analog to Digital) conversion section  433 - 1 . 
     Orthogonal demodulation section  431 - 1  performs an orthogonal demodulation process on the signal of the “A system” received via antenna  410 - 1 , and generates a baseband IQ signal of the “A system”. Orthogonal demodulation section  431 - 1  outputs the baseband IQ signal of the “A system” to variable gain section  432 - 1 . 
     Variable gain section  432 - 1  adjusts the level of the baseband IQ signal of the “A system”. Specifically, variable gain section  432 - 1  adjusts the level of the baseband IQ signal of the “A system” based on a gain designated by gain control section  450 - 1  (hereinafter referred to as “first gain”). Variable gain section  432 - 1  outputs the baseband IQ signal of the “A system” after the level adjustment, to AD conversion section  433 - 1 . 
     AD conversion section  433 - 1  converts the analog baseband IQ signal of the “A system” after the level adjustment, into a digital signal. AD conversion section  433 - 1  outputs the digital IQ signal of the “A system” after the conversion, to demodulation section  440 - 1  and gain control section  450 - 1 . 
     Demodulation section  440 - 1  demodulates the digital IQ signal of the “A system”. 
     Gain control section  450 - 1  adjusts the gain of variable gain section  432 - 1  (the first gain) while monitoring the power of the digital IQ signal of the “A system”. Specifically, gain control section  450 - 1  sets the first gain such that the power of the digital IQ signal of the “A system” remains constant. The internal configuration and operations of gain control section  450 - 1  will be described later. 
     Reception processing section  420 - 1  for the “A system” thus uses the output of variable gain section  432 - 1  to perform an AGC process in which gain control section  450 - 1  adjusts the gain of variable gain section  432 - 1  (this is, the first gain). 
     Initial gain setting section  460  sets an initial gain to be used by variable gain section  432 - 2  at the start of the gain adjustment (hereinafter referred to as “converted second initial gain”), based on the first gain. A method of setting the converted second initial gain will be described later. Initial gain setting section  460  outputs information on the set converted second initial gain, to gain control section  450 - 2 . 
     Reception processing section for the “B system”  420 - 2  includes high-frequency circuit  430 - 2 , demodulation section  440 - 2  and gain control section  450 - 2 . 
     High-frequency circuit  430 - 2  includes orthogonal demodulation section  431 - 2 , variable gain section  432 - 2  and AD conversion section  433 - 2 . 
     Orthogonal demodulation section  431 - 2  performs the orthogonal demodulation process on the signal of the “B system” received via antenna  410 - 2 , and generates a baseband IQ signal of the “B system”. Orthogonal demodulation section  431 - 2  outputs the baseband IQ signal of the “B system” to variable gain section  432 - 2 . 
     Variable gain section  432 - 2  adjusts the level of the baseband IQ signal of the “B system”. Specifically, variable gain section  432 - 2  adjusts the level of the baseband IQ signal of the “B system” based on a gain specified by gain control section  450 - 2  (hereinafter referred to as “second gain”). Variable gain section  432 - 2  outputs the baseband IQ signal of the “B system” after the level adjustment, to AD conversion section  433 - 2 . 
     AD conversion section  433 - 2  converts the analog baseband IQ signal of the “B system” after the level adjustment, into a digital signal. AD conversion section  433 - 2  outputs the digital IQ signal of the “B system” after the conversion, to demodulation section  440 - 2  and gain control section  450 - 2 . 
     Demodulation section  440 - 2  demodulates the digital IQ signal of the “B system”. 
     Gain control section  450 - 2  adjusts the gain of variable gain section  432 - 2  (that is, the second gain) while monitoring the power of the digital IQ signal of the “B system”. Specifically, gain control section  450 - 2  uses the converted second initial gain set by initial gain setting section  460 , as the initial gain at the start of the gain adjustment. Gain control section  450 - 2  then sets the second gain such that the power of the digital IQ signal of the “B system” remains constant. The internal configuration and operations of gain control section  450 - 2  will be described later. 
     Reception processing section  420 - 2  for the “B system” thus uses the output of variable gain section  432 - 2  to perform the AGC process in which gain control section  450 - 2  adjusts the gain of variable gain section  432 - 2  (that is, the second gain). 
       FIG. 3  is a diagram illustrating an example of the internal configuration of gain control section  450 - 1  in reception processing section  420 - 1  for the “A system”. 
     Gain control section  450 - 1  includes IQ power measurement section  451 - 1 , initial gain storage section  452 - 1 , and adjustment section  453 - 1 , and adjusts the gain of variable gain section  432 - 1  (the first gain). 
     IQ power measurement section  451 - 1  measures a power value of the digital IQ signal of the “A system”, and outputs the measured power value to adjustment section  453 - 1 . 
     Initial gain storage section  452 - 1  stores an initial gain to be used by variable gain section  432 - 1  at the start of the gain adjustment (hereinafter referred to as “first initial gain”). Initial gain storage section  452 - 1  then outputs information on the first initial gain to adjustment section  453 - 1 , at the start of the gain adjustment. 
     Adjustment section  453 - 1  adjusts the gain of variable gain section  432 - 1  (the first gain) based on the power value of the digital IQ signal of the “A system”. Adjustment section  453 - 1  outputs the information on the first initial gain, as information on the first gain, to variable gain section  432 - 1  at the start of the gain adjustment. 
     Adjustment section  453 - 1  includes coarse adjustment section  454 - 1  and fine adjustment section  455 - 1 . 
     Coarse adjustment section  454 - 1  coarsely adjusts the gain of variable gain section  432 - 1  based on the power value of the digital IQ signal of the “A system”. 
     Fine adjustment section  455 - 1  finely adjusts the gain of variable gain section  432 - 1 , within an adjustment range smaller than a gain adjustment range in coarse adjustment section  454 - 1 . 
     Adjustment section  453 - 1  then sets the final first gain while adjusting the first gain in coarse adjustment section  454 - 1  and fine adjustment section  455 - 1 . Adjustment section  453 - 1  outputs information on the set final first gain to initial gain setting section  460 . 
       FIG. 4  is a diagram illustrating an example of the internal configuration of gain control section  450 - 2  in reception processing section  420 - 2  for the “B system”. 
     Gain control section  450 - 2  includes IQ power measurement section  451 - 2 , initial gain storage section  452 - 2 , adjustment section  453 - 2 , and selection section  456 , and adjusts the gain of variable gain section  432 - 2  (the second gain). 
     IQ power measurement section  451 - 2  measures a power value of the digital IQ signal of the “B system”, and outputs the measured power value to adjustment section  453 - 2 . 
     Initial gain storage section  452 - 2  stores an initial gain to be normally used by variable gain section  432 - 2  at the start of the gain adjustment (hereinafter referred to as “normal converted second initial gain”). Initial gain storage section  452 - 2  then outputs information on the normal converted second initial gain to selection section  456 , at the start of the gain adjustment. 
     Information on a normal converted second initial gain is input to selection section  456  from initial gain storage section  452 - 2 . In addition, the information on the converted second initial gain is input to selection section  456  from initial gain setting section  460 . If the information on the converted second initial gain is input from initial gain setting section  460 , selection section  456  outputs the information on the converted second initial gain, as information on a second initial gain, to adjustment section  453 - 2 . In contrast, if the information on the converted second initial gain is not input from initial gain setting section  460 , selection section  456  outputs the information on the normal converted second initial gain, as the information on the second initial gain, to adjustment section  453 - 2 . 
     Adjustment section  453 - 2  adjusts the gain of variable gain section  432 - 2  based on the power value of the digital IQ signal of the “B system”. The information on the second initial gain is input to adjustment section  453 - 2  from selection section  456 . Adjustment section  453 - 2  outputs the information on the second initial gain, as information on the second gain, to variable gain section  432 - 2  at the start of the gain adjustment. Adjustment section  453 - 2  then adjusts the second gain based on the digital IQ signal of the “B system”. 
     Adjustment section  453 - 2  includes coarse adjustment section  454 - 2  and fine adjustment section  455 - 2 . 
     Coarse adjustment section  454 - 2  performs the coarse adjustment on the gain of variable gain section  432 - 2 . 
     Fine adjustment section  455 - 2  performs the fine adjustment on the gain of variable gain section  432 - 2 , within an adjustment range smaller than a gain adjustment range in coarse adjustment section  454 - 2 . 
     Adjustment section  453 - 2  then sets the final second gain of variable gain section  432 - 2  while adjusting the second gain in coarse adjustment section  454 - 2  and fine adjustment section  455 - 2 . 
     Operations of wireless device  400  will be described next. 
       FIG. 5  is a flowchart illustrating an example of the operations of wireless device  400 . 
     In step S 101 , antenna  410 - 1  receives the signal of the “A system” transmitted from wireless device # 2   300  (not illustrated). 
     In step S 102 , orthogonal demodulation section  431 - 1  performs the orthogonal demodulation process on the signal of the “A system”, and generates the baseband IQ signal of the “A system”. 
     In step S 103 , variable gain section  432 - 1  adjusts the level of the baseband IQ signal of the “A system”. 
     In step S 104 , gain control section  450 - 1  then adjusts the gain of variable gain section  432 - 1  (that is, the first gain), based on the baseband IQ signal of the “A system” after the level adjustment. 
     In step S 105 , initial gain setting section  460  sets the initial gain of gain control section  450 - 2  (that is, the converted second initial gain), based on the gain of variable gain section  432 - 1  (that is, the first gain) set by gain control section  450 - 1 . The method of setting the converted second initial gain will be described later. 
     In step S 106 , antenna  410 - 2  receives the signal of the “B system” transmitted from wireless device # 2   300  (not illustrated). 
     In step S 107 , orthogonal demodulation section  431 - 2  performs the orthogonal demodulation process to generate the baseband IQ signal of the “B system”. 
     In step S 108 , variable gain section  432 - 2  adjusts the level of the baseband IQ signal of the “B system”. 
     In step S 109 , gain control section  450 - 2  then adjusts the gain of variable gain section  432 - 2  (the second gain), based on the baseband IQ signal of the “B system” after the level adjustment. 
     In  FIG. 1 , signals of the A and B systems leave wireless device # 2   300 , pass through the same propagation path, and arrive at wireless device # 1   200 . The reception levels of the signals of the A and B systems then decrease due to propagation losses. As described above, gain control section  450 - 1  adjusts the gain of variable gain section  432 - 1  (that is, the first gain) such that the power of the digital IQ signal of the “A system” that is input to demodulation section  440 - 1  remain constant. In other words, gain control section  450 - 1  adjusts the gain of variable gain section  432 - 1  (that is, the first gain) to be a value that compensates for the propagation loss of the signal of the “A system”. Thus, the gain of variable gain section  432 - 1  (that is, the first gain), adjusted by gain control section  450 - 1 , includes information on the propagation loss. 
     Accordingly, initial gain setting section  460  sets the gain to be used by variable gain section  432 - 2  (the converted second initial gain), based on the first gain, at the start of the gain adjustment. Gain control section  450 - 2  thereby starts the gain adjustment with the converted second initial gain suitable for compensating for the propagation loss, and thus reduces the time required for the gain adjustment in variable gain section  432 - 2 . Wireless device  400  thereby increases the time to be assigned to establishment of timing synchronization and an AFC process in a preamble period, and improve communication performance. 
     The method of setting the converted second initial gain in initial gain setting section  460  will be described next. 
     The case of variable gain sections  432 - 1  and  432 - 2  including multiple VGAs (Variable Gain Amplifiers) will be considered below. In addition, the case of variable gain sections  432 - 1  and  432 - 2  having the same internal configuration will be described by way of example. 
       FIG. 6  is a block diagram illustrating an example of the configuration of variable gain sections  432 - 1  and  432 - 2 . Variable gain sections  432 - 1  and  432 - 2  of  FIG. 6  include VGA[ 0 ] to VGA[ 5 ]. Among them, VGA[ 0 ] to VGA[ 2 ] are VGAs for the fine adjustment, while VGA[ 3 ] to VGA[ 5 ] are those for the coarse adjustment. 
     VGA[ 0 ] to VGA[ 5 ] switch between whether or not to amplify the input signal, depending on gain setting values C[ 0 ] to C[ 5 ]. If C[k]=1, for example, VGA[k] amplifies the amplitude level of the input signal by 2 k  dB. In contrast, if C[k]=0, VGA[k] directly outputs the input signal without an amplification operation. 
     [Setting Method #1-1] 
     Initial gain setting section  460  directly sets the first gain to the converted second initial gain of variable gain section  432 - 2 . 
     Gain control section  450 - 1 , for example, is assumed to have set the gain setting values C[ 0 ] to C[ 5 ] of VGA[ 0 ] to VGA[ 5 ] in variable gain section  432 - 1  (the first gain) as follows:
         C[ 5 ]=1, C[ 4 ]=0, C[ 3 ]=1, C[ 2 ]=0, C[ 1 ]=1, C[ 0 ]=0.       

     Initial gain setting section  460  then directly sets the above setting to the converted second initial gain of VGA[ 0 ] to VGA[ 5 ] included in variable gain section  432 - 2 . 
     Gain control section  450 - 2  then starts the gain adjustment with the converted second initial gain to adjust the gain of variable gain section  432 - 2  (that is, the second gain) such that the amplitude level of the digital IQ signal of the “B system” remains constant. 
     In Setting Method #1-1, gain control section  460  thus directly sets the gain of variable gain section  432 - 1  (the first gain) that has already been adjusted by gain control section  450 - 1 , to the converted second initial gain. Variable gain section  432 - 2  then uses the first gain of variable gain section  432 - 1 , for the converted second initial gain, and performs the level adjustment. If frequencies of the A and B systems are close to each other and a difference between the propagation losses of the signals of the A and B systems is small, for example, gain control section  450 - 2  can complete the gain adjustment in a short time. 
     [Setting Method #1-2] 
     Initial gain setting section  460  sets an initial gain of coarse adjustment section  454 - 2  based on the first gain. 
     Gain control section  450 - 1 , for example, is assumed to have set the gain setting values C[ 0 ] to C[ 5 ] of VGA[ 0 ] to VGA[ 5 ] in variable gain section  432 - 1  (the first gain) as follows:
         C[ 5 ]=1, C[ 4 ]=0, C[ 3 ]=1, C[ 2 ]=0, C[ 1 ]=1, C[ 0 ]=0.       

     Initial gain setting section  460  then sets the converted second initial gain that has at least C[ 5 ]=1, C[ 4 ]=0 and C[ 3 ]=1, among the gain setting values C[ 0 ] to C[ 5 ] of VGA[ 0 ] to VGA[ 5 ] in variable gain section  432 - 2 . 
     In Setting Method #1-2, variable gain section  432 - 2  thus uses the initial gain of the VGAs for the coarse adjustment in variable gain section  432 - 1 , in the first gain, for the initial gain of the VGAs for the coarse adjustment in variable gain section  432 - 2 , and performs the level adjustment. The first gain includes the information on the propagation loss as described above. Accordingly, for example, even if the A and B systems have different frequencies and propagation losses, gain control section  450 - 2  can start the gain adjustment with the converted second initial gain suitable for compensating for the propagation loss. Gain control section  450 - 2  can thereby reduce the time required for the gain adjustment. 
     Setting Methods #1-1 and #1-2 are preferred in the case of variable gain sections  432 - 1  and  432 - 2  having the same internal configuration. 
     Additionally, setting methods applicable in the case of variable gain sections  432 - 1  and  432 - 2  (that is, Setting Methods #1-3 and #1-4) have different internal configurations and will be described next. 
       FIG. 7  is a block diagram illustrating an example of the configurations of variable gain sections  432 - 1  and  432 - 2 . 
     Variable gain section  432 - 1  of  FIG. 7A  includes VGA[ 0 ] to VGA[ 5 ]. Among them, VGA[ 0 ] to VGA[ 2 ] are the VGAs for the fine adjustment, while VGA[ 3 ] to VGA[ 5 ] are those for the coarse adjustment. 
     VGA[ 0 ] to VGA[ 5 ] switch between whether or not to amplify the input signal, depending on the gain setting values C[ 0 ] to C[ 5 ]. If C[k]=1, for example, VGA[k] amplifies the amplitude level of the input signal by 2 k  dB. In contrast, if C[k]=0, VGA[k] directly outputs the input signal without the amplification operation. 
     Variable gain section  432 - 2  of  FIG. 7B  includes VGA[ 6 ] to VGA[ 9 ]. Among them, VGA[ 6 ] and VGA[ 7 ] are the VGAs for the fine adjustment, while VGA[ 8 ] and VGA[ 9 ] are those for the coarse adjustment. 
     VGA[ 6 ] to VGA[ 9 ] switch between whether or not to amplify the input signal, depending on gain setting values C[ 6 ] to C[ 9 ]. If C[k]=1, for example, VGA[k] amplifies the amplitude level of the input signal by 3 k  dB. In contrast, if C[k]=0, VGA[k] directly outputs the input signal without the amplification operation. 
     [Setting Method #1-3] 
     Initial gain setting section  460  compares the first gain with a predetermined range, and based on a result of the comparison, selects a candidate from a list of candidates for the converted second initial gain of variable gain section  432 - 2 . Initial gain setting section  460  then sets the selected candidate to the converted second initial gain of variable gain section  432 - 2 . 
     Specifically, initial gain setting section  460  compares the first gain with the predetermined range, and determines the electric field level of the propagation path. Initial gain setting section  460  then sets the converted second initial gain of variable gain section  432 - 2 , depending on the determined electric field level. 
     Initial gain setting section  460 , for example, compares the first gain with the eleventh range (from 0 dB to 20 dB), the twelfth range (from 21 dB to 42 dB), and the thirteenth range (from 43 dB to 63 dB). If the first gain is in the eleventh range (from 0 dB to 20 dB), in the twelfth range (from 21 dB to 42 dB), or in the thirteenth range (from 43 dB to 63 dB), the initial gain setting section  460  is assumed to determine the electric field level to be a strong electric field level, a medium electric field level, or a weak electric field level, respectively. 
     Gain control section  450 - 1  is assumed to have set the gain setting values C[ 0 ] to C[ 5 ] of VGA[ 0 ] to VGA[ 5 ] in variable gain section  432 - 1  (that is, the first gain) as follows:
         C[ 5 ]=1, C[ 4 ]=0, C[ 3 ]=1, C[ 2 ]=0, C[ 1 ]=1, C[ 0 ]=0.       

     According to the above setting, the first gain of variable gain section  432 - 1  becomes 26(=32×1+16×0+8×1+4×0+2×1+1×0) dB. 
     Accordingly, initial gain setting section  460  determines that the electric field level of the propagation path is the medium electric field level, based on the result of the comparison between the first gain (=26 dB) and the above ranges. 
     After determining the electric field level from the first gain, initial gain setting section  460  then sets the converted second initial gain depending on a result of the determination. 
     It is assumed that, for example, there are three candidates G 21 , G 22  and G 23  in the list of candidates for the initial gain C[ 9 : 6 ] of coarse adjustment section  454 - 2 . For example, G 21  is assumed to be C[ 9 ]=0, C[ 8 ]=1, C[ 7 ]=0, C[ 6 ]=1. G 22  is assumed to be C[ 9 ]=1, C[ 8 ]=0, C[ 7 ]=0, C[ 6 ]=0. G 23  is assumed to be C[ 9 ]=1, C[ 8 ]=1, C[ 7 ]=0, C[ 6 ]=0. 
     In the case of the weak electric field level, initial gain setting section  460  sets the initial gain of coarse adjustment section  454 - 2  to G 21 . In the case of the medium electric field level, initial gain setting section  460  sets the initial gain of coarse adjustment section  454 - 2  to G 22 . In the case of the strong electric field level, initial gain setting section  460  sets the initial gain of coarse adjustment section  454 - 2  to G 23 . 
     In Setting Method #1-3, initial gain setting section  460  thus classifies the status of the propagation path into the strong electric field level, the medium electric field level, or the weak electric field level, based on the first gain. Initial gain setting section  460  then sets the initial gain of variable gain section  432 - 2  (the converted second initial gain), depending on the status of the propagation path. The first gain includes the information on the propagation loss as described above. Initial gain setting section  460  then determines the status of the propagation path depending on the first gain, and sets the converted second initial gain suitable for the status of the propagation path. Accordingly, even in the case of variable gain sections  432 - 1  and  432 - 2  having the different internal configurations, gain control section  450 - 2  can start the gain adjustment with the converted second initial gain suitable for compensating for the propagation loss. Gain control section  450 - 2  can thereby reduce the time required for the gain adjustment. 
     In the above description, initial gain setting section  460  classifies the electric field level into three classes depending on the first gain, and selects the candidate from the three candidates for the initial gain depending on the electric field level, which is not limited thereto. The number of classes into which the electric field level is classified, and the number of candidates for the converted second initial gain depend on requested precision of variable gain section  432 - 2 . 
     In addition, in the above described case, initial gain setting section  460  sets only the initial gain of coarse adjustment section  454 - 2  depending on the electric field level, which is not limited thereto. Initial gain setting section  460  may set the initial gains of coarse adjustment section  454 - 2  and fine adjustment section  455 - 2 , depending on the electric field level. 
     Setting Method #1-3 is also applicable to the case of variable gain sections  432 - 1  and  432 - 2  having the same internal configuration. 
     [Setting Method #1-4] 
     In Setting Method #1-4, initial gain setting section  460  stores a table that includes the first gain associated with the corresponding second gain, and sets the initial gain of variable gain section  432 - 2  (that is, the converted second initial gain) based on the first gain. 
       FIG. 8  is a diagram illustrating an example of the table stored in initial gain setting section  460 . The first gain is associated with the corresponding second gain based on the effects of the propagation losses through the propagation path and due to the difference between the frequencies of the signals of the A and B systems. In other words, this table includes a first gain associated with a corresponding second gain that is obtained by applying a frequency characteristic conversion to the first gain and depending on the difference between the propagation losses of the signals of the A and B systems. 
     Initial gain setting section  460  then selects the second gain associated with the first gain from this table, and sets the selected second gain to the initial gain of variable gain section  432 - 2  (that is, the converted second initial gain). 
     In Setting Method #1-4, initial gain setting section  460  thus sets the gain obtained by applying the frequency characteristic conversion to the first gain, to the converted second initial gain, depending on the difference between the propagation losses of the signals of the A and B systems. Accordingly, even in the case of variable gain sections  432 - 1  and  432 - 2  having the different internal configurations, gain control section  450 - 2  can start the gain adjustment with the converted second initial gain suitable for compensating for the propagation loss. The time required for gain adjustment is thereby reduced. Setting Method #1-4 is also applicable to the case of variable gain sections  432 - 1  and  432 - 2  having the same internal configuration. 
     As described above, in wireless device  400  according to the present embodiment, initial gain setting section  460  sets the converted second initial gain based on the first gain. Here, the first gain is the gain of variable gain section  432 - 1  that has been adjusted by gain control section  450 - 1 . The converted second initial gain is the initial gain of variable gain section  432 - 2  at the start of the gain adjustment. 
     Gain control section  450 - 2  then sets this converted second initial gain to the second gain at the start of the gain adjustment, and adjusts the second gain based on the IQ signal of the “B system” whose level has been adjusted by variable gain section  432 - 2 . Wireless device  400  thereby starts the gain adjustment with the converted second initial gain suitable for compensating for the propagation loss and reduces the time required for the gain adjustment. In other words, wireless device  400  can reduce time required for the AGC process. Wireless device  400  therefore improves the communication performance by an increase in the time available for AFC processing and the timing synchronization process in the preamble period. 
     After the converted second initial gain is set, only fine adjustment section  455 - 2  may perform the gain adjustment, without coarse adjustment section  454 - 2 . This reduces power consumption in subsequent gain adjustment without coarse adjustment section  454 - 2 . 
     (Embodiment 2) 
       FIG. 9  is a block diagram illustrating the configuration of the wireless device according to the present embodiment. Wireless device  500  of  FIG. 9  is applied to wireless device # 1  ( 200 ) of  FIG. 1 . In  FIG. 9 , components common to  FIG. 2  are assigned the same reference numerals as  FIG. 2 , and descriptions thereof will be omitted. In contrast to wireless device  400  of  FIG. 2 , wireless device  500  of  FIG. 9  includes reception processing section for the “A system”  510 - 1 , and reception processing section for the “B system”  510 - 2 , instead of reception processing section for the “A system”  420 - 1 , and reception processing section for the “B system”  420 - 2 . In contrast to wireless device  400  of  FIG. 2 , wireless device  500  of  FIG. 9  also includes initial gain setting section  530  instead of initial gain setting section  460 . 
     In contrast to reception processing section for the “A system”  420 - 1 , reception processing section for the “A system”  510 - 1  includes gain control section  520 - 1  instead of gain control section  450 - 1 . 
     Gain control section  520 - 1  adjusts the gain of variable gain section  432 - 1  (that is, the first gain) while monitoring the power of the digital IQ signal of the “A system,” similarly to gain control section  450 - 1 . Gain control section  520 - 1  further estimates received power of the signal of the “A system” at the end of antenna  410 - 1  (hereinafter also referred to as “received power of the ‘A system’”), based on the digital IQ signal of the “A system” and the information on the final first gain. Gain control section  520 - 1  then outputs information on the received power of the “A system,” to initial gain setting section  530 . The internal configuration and operations of gain control section  520 - 1  will be described later. 
     Initial gain setting section  530  sets the initial gain of variable gain section  432 - 2  (that is, the converted second initial gain), based on the received power of the “A system” during communication. The method of setting the converted second initial gain will be described later. 
     In contrast to reception processing section for the “B system”  420 - 2 , reception processing section for the “B system” 510 - 2  includes gain control section  520 - 2  instead of gain control section  450 - 2 . 
     Gain control section  520 - 2  adjusts the gain of variable gain section  432 - 2  (the second gain) while monitoring the power of the digital IQ signal of the “B system”. Specifically, gain control section  520 - 2  uses the converted second initial gain set by initial gain setting section  530 , as the initial gain at the start of the gain adjustment during wireless communication using the “B system”. Gain control section  520 - 2  then sets the second gain such that the power of the digital IQ signal of the “B system” remains constant. The internal configuration and operations of gain control section  520 - 2  will be described later. 
       FIG. 10  is a diagram illustrating an example of the internal configuration of gain control section  520 - 1  in reception processing section for the “A system”  510 - 1 . In  FIG. 10 , components common to  FIG. 3  are assigned the same reference numerals as  FIG. 3 , and detailed descriptions thereof will be omitted. 
     Gain control section  520 - 1  includes IQ power measurement section  451 - 1 , initial gain storage section  452 - 1 , adjustment section  453 - 1 , and received power estimation section  521 - 1 . 
     IQ power measurement section  451 - 1  measures the power value of the digital IQ signal of the “A system”, and outputs the measured power value to adjustment section  453 - 1  and received power estimation section  521 - 1 . 
     Adjustment section  453 - 1  sets the final first gain while adjusting the first gain in coarse adjustment section  454 - 1  and fine adjustment section  455 - 1 . Adjustment section  453 - 1  outputs the information on the set final first gain to received power estimation section  521 - 1 . 
     Received power estimation section  521 - 1  estimates the received power of the signal of the “A system” at the end of antenna  410 - 1  (that is, the received power of the “A system”), based on the power value of the digital IQ signal of the “A system” and the information on the final first gain. Received power estimation section  521 - 1  then outputs the information on the received power of the “A system,” to initial gain setting section  530 . 
       FIG. 11  is a diagram illustrating an example of the internal configuration of gain control section  520 - 2  in reception processing section for the “B system”  510 - 2 . In  FIG. 11 , components common to  FIG. 4  are assigned the same reference numerals as  FIG. 4 , and detailed descriptions thereof will be omitted. 
     Gain control section  520 - 2  includes IQ power measurement section  451 - 2 , initial gain storage section  452 - 2 , adjustment section  453 - 2 , selection section  456 , and received power estimation section  521 - 2 . Received power estimation section  521 - 2  does not operate in the actual communication, but operates only at the time of preadjustment (that is, prior to actual communication). 
     IQ power measurement section  451 - 2  measures the power value of the digital IQ signal of the “B system,” and outputs the measured power value to adjustment section  453 - 2 . IQ power measurement section  451 - 2  outputs the measured power value to adjustment section  453 - 2  and received power estimation section  521 - 2  only at the time of the preadjustment. 
     Adjustment section  453 - 2  sets the final second gain of variable gain section  432 - 2  while adjusting the second gain. 
     Received power estimation section  521 - 2  estimates received power of the signal of the “B system” at the end of antenna  410 - 2  (that is, the received power of the “B system”), based on the power value of the digital IQ signal of the “B system” and the information on the second gain, at the time of the preadjustment. Received power estimation section  521 - 2  then outputs the information on the received power of the “B system,” to initial gain setting section  530 . 
     The method of setting the converted second initial gain in initial gain setting section  530  will be described next. 
     [Setting Method #2-1] 
     Received power estimation sections  521 - 1  and  521 - 2  estimate the received power of the signals of the A and B systems, at the time of the preadjustment, in two cases of a long distance between wireless device  500  (that is, wireless device # 1 ) and transmitter wireless device # 2 , and of a short distance therebetween. 
     Initial gain setting section  530  stores the following information (P 1 , Q 1 , P 2 , Q 2 ) into an internal memory: 
     P 1 : A difference between the transmitted power and the received power of the signal of the “A system” in the case of the long distance between wireless device # 1  and wireless device # 2 . 
     Q 1 : A difference between the transmitted power and the received power of the signal of the “B system” in the case of the long distance between wireless device # 1  and wireless device # 2 . 
     P 2 : The difference between the transmitted power and the received power of the signal of the “A system” in the case of the short distance between wireless device # 1  and wireless device # 2 . 
     Q 2 : The difference between the transmitted power and the received power of the signal of the “B system” in the case of the short distance between wireless device # 1  and wireless device # 2 . 
     The information on the received power of the signal of the “A system” is input to initial gain setting section  530  during communication. Initial gain setting section  530  then calculates a difference P 3  between the transmitted power and this received power of the signal of the “A system”. 
     Initial gain setting section  530  then estimates a difference Q 3  between the transmitted power and the received power of the signal of the “B system,” based on the difference P 3  between the transmitted power and this received power of the signal of the “A system”. 
     Specifically, assuming that the difference between the transmitted power and the received power has linearity, initial gain setting section  530  estimates the difference Q 3  between the transmitted power and the received power of the signal of the “B system”. 
       FIG. 12  is a diagram illustrating a relationship among the differences P 1 , Q 1 , P 2 , Q 2 , P 3  and Q 3 . As illustrated in  FIG. 12 , initial gain setting section  530  estimates the difference Q 3  by using Equations 1 and 2, according to a relationship between the differences P 1 , Q 1 , P 2  and Q 2  previously obtained at the time of the preadjustment, and the difference P 3  obtained during communication.
 
( Q 3 −Q 1)=( Q 2 −Q 1)( P 3 −P 1)/( P 2 −P 1)  (Equation 1)
 
 Q 3=( Q 2 −Q 1)( P 3 −P 1)/( P 2 −P 1)+ Q 1  (Equation 2)
 
     The difference Q 3  indicates an estimated value of the propagation loss of the signal of the “B system” through the propagation path. 
     Initial gain setting section  530  then sets the initial gain of variable gain section  432 - 2  (that is, the converted second initial gain) depending on the difference Q 3 . 
     In Setting Method #2-1, initial gain setting section  530  thus previously obtains association between a difference PA between the transmitted power and the received power of the signal of the “A system,” and a difference PB between the transmitted power and the received power of the signal of the “B system”. Initial gain setting section  530  then estimates the difference Q 3  based on this association and the difference P 3 . Here, the difference P 3  is a difference between the transmitted power of one signal of the “A system” and the received power of the signal of the “A system” that has been estimated by received power estimation section  521 - 1 . The difference Q 3  is the difference between the transmitted power and the received power of the signal of the “B system”. Initial gain setting section  530  then sets the converted second initial gain based on the estimated difference Q 3 . Initial gain setting section  530  thus sets the gain suitable for compensating for the propagation loss of the signal of the “B system,” to the converted second initial gain, from the received power of the “A system”. Gain control section  520 - 2  can thereby reduce the time required for the gain adjustment. 
     [Setting Method #2-2] 
     In Setting Method #2-1, initial gain setting section  530  used Equation (2) to estimate the received power of the signal of the “B system,” from the received power of the signal of the “A system”. In Setting Method #2-2, instead of Equation (2), initial gain setting section  530  sets the converted second initial gain by using an association table of PA and PB, where the difference PA between the transmitted power and the received power of the signal of the “A system,” is associated with the corresponding difference PB between the transmitted power and the received power of the signal of the “B system,”. 
     Received power estimation sections  521 - 1  and  521 - 2  estimate the received power of the signals of the A and B systems, at multiple distances between wireless device  500  (that is, wireless device # 1 ) and transmitter wireless device # 2 , at the time of the preadjustment. 
     Initial gain setting section  530  stores a table including the difference PA associated with the difference PB at each of the multiple distances between wireless device  500  (wireless device # 1 ) and transmitter wireless device # 2 , into the internal memory. Here, the difference PA is the difference between the transmitted power and the received power of the signal of the “A system”. The difference PB is the difference between the transmitted power and the received power of the signal of the “B system”. 
       FIG. 13  is a diagram illustrating an example of the table stored in initial gain setting section  530 . Initial gain setting section  530  stores the table including the difference PA associated with the corresponding difference PB at each distance. 
     The information on the received power of the signal of the “A system” is input to initial gain setting section  530  in the actual communication. Initial gain setting section  530  then calculates the difference P 3  between the transmitted power and this received power of the signal of the “A system”. 
     Initial gain setting section  530  then estimates the difference Q 3  between the transmitted power and the received power of the signal of the “B system,” based on the difference P 3  between the transmitted power and this received power of the signal of the “A system,” with reference to the above table. 
     Subsequently, initial gain setting section  530  sets the converted second initial gain of variable gain section  432 - 2 , depending on the difference Q 3 , similar to Setting Method #2-1. 
     In Setting Method #2-2, initial gain setting section  530  stores the table including the difference PA associated with the corresponding difference PB. Initial gain setting section  530  then sets the converted second initial gain, based on the difference PB associated with the difference between the transmitted power of the signal of the “A system” and the received power of the signal of the “A system” that has been estimated by received power estimation section  521 - 1 . 
     Initial gain setting section  530  thus sets the gain suitable for compensating for the propagation loss of the signal of the “B system”, to the converted second initial gain, from the received power of the “A system”. Gain control section  520 - 2  thereby reduces the time required for the gain adjustment. 
     [Setting Method #2-3] 
     Initial gain setting section  530  determines the electric field level of the propagation path, from the received power of the signal of the “A system”. Initial gain setting section  530  then sets the converted second initial gain of variable gain section  432 - 2  depending on the determined electric field level. 
     Initial gain setting section  530 , for example, compares the received power of the signal of the “A system” with the twenty-first range (from 43 dB to 63 dB), the twenty-second range (from 21 dB to 42 dB), and the twenty-third range (from 0 dB to 20 dB). The received power of the signal of the “A system,” for example, is assumed to be in the twenty-first range (from 43 dB to 63 dB), in the twenty-second range (from 21 dB to 42 dB), or in the twenty-third range (from 0 dB to 20 dB). In this case, initial gain setting section  530  is assumed to determine the electric field level to be the strong electric field level, the medium electric field level, or the weak electric field level, respectively. 
     Now, the received power of the signal of the “A system” is assumed to be 38 dB. In this case, initial gain setting section  530  determines that the electric field level of the propagation path is the medium electric field level, from the received power of the signal of the “A system” (=38 dB). 
     After determining the electric field level from the received power of the signal of the “A system,” initial gain setting section  530  then sets the initial gain of coarse adjustment section  454 - 2  depending on a result of the determination. 
     A method of setting the initial gain of coarse adjustment section  454 - 2  is similar to Setting Method #1-3, and thus a description thereof will be omitted. 
     In Setting Method #2-3, initial gain setting section  530  thus classifies the status of the propagation path into the strong electric field level, the medium electric field level, or the weak electric field level, based on the received power of the signal of the “A system”. Initial gain setting section  530  then sets the initial gain of variable gain section  432 - 2  (that is, the converted second initial gain) depending on the status of the propagation path. The received power of the signal of the “A system” includes the information on the propagation loss as described above. Initial gain setting section  530  then determines the status of the propagation path depending on the received power of the signal of the “A system,” and sets the converted second initial gain suitable for the status of the propagation path. Accordingly, gain control section  520 - 2  starts the gain adjustment with the converted second initial gain suitable for compensating for the propagation loss. Gain control section  520 - 2  thereby reduces the time required for the gain adjustment. Since Setting Method #2-3 does not need the estimation of the received power of the signal of the “B system” during communication and at the time of the preadjustment, gain control section  520 - 2  can employ a configuration without received power estimation section  521 - 2 . 
     [Setting Method #2-4] 
     In Setting Method #2-4, initial gain setting section  530  stores a table including the difference PA associated with the corresponding second gain, and sets the initial gain of variable gain section  432 - 2  (that is, the converted second initial gain) based on the difference PA. 
       FIG. 14  is a diagram illustrating an example of the table stored in initial gain setting section  530 . The difference PA is associated with the corresponding second gain based on the effects of the propagation losses through the propagation path and due to the difference between the frequencies of the signals of the A and B systems. In other words, this table includes the difference PA associated with the corresponding second gain required for compensating for the difference PB obtained by applying the frequency characteristic conversion to the difference PA, depending on the difference between the propagation losses of the signals of the A and B systems. 
     Initial gain setting section  530  then selects the second gain associated with the difference PA, from this table, and sets the selected second gain to the initial gain of variable gain section  432 - 2  (that is, the converted second initial gain). 
     In Setting Method #2-4, initial gain setting section  530  thus stores the table including the difference PA associated with the corresponding second gain, depending on the propagation losses of the signals of the A and B systems through the propagation path. Initial gain setting section  530  then sets the second gain associated with the corresponding difference P 3  between the transmitted power of the signal of the “A system” and the received power of the signal of the “A system” that has been estimated by received power estimation section  521 - 1 , to the converted second initial gain. Accordingly, gain control section  520 - 2  starts the gain adjustment with the converted second initial gain suitable for compensating for the propagation loss. Gain control section  520 - 2  thereby reduces the time required for the gain adjustment, since Setting Method #2-4 does not need the estimation of the received power of the signal of the “B system” during communication and at the time of the preadjustment. Gain control section  520 - 2  therefore employs a configuration without received power estimation section  521 - 2 . 
     As described above, in wireless device  500  according to the present embodiment, initial gain setting section  530  sets the converted second initial gain based on the received power of the signal of the “A system”. Gain control section  520 - 2  then sets this converted second initial gain to the second gain at the start of the gain adjustment, and adjusts the second gain based on the IQ signal of the “B system” whose level has been adjusted by variable gain section  432 - 2 . Wireless device  500  thereby starts the gain adjustment with the converted second initial gain suitable for compensating for the propagation loss, and reduces the time required for the gain adjustment. In other words, wireless device  500  reduces the time required for AGC processing. Wireless device  500  therefore improves the communication performance according to an increase in the time available for the AFC process and the timing synchronization process in the preamble period. 
     After the converted second initial gain is set, only fine adjustment section  455 - 2  may perform the gain adjustment, without coarse adjustment section  454 - 2 . The present embodiment thereby reduces the power consumption in the subsequent gain adjustment without coarse adjustment section  454 - 2 . 
     The entire content of the disclosure of the description, drawings and abstract included in Japanese Patent Application No. 2011-048965 filed on Mar. 7, 2011 is incorporated herein by reference. 
     Industrial Applicability 
     The wireless device and the reception method according to the present invention are useful for wireless devices capable of multiple wireless schemes and the like. 
     Reference Signs List 
     
         
           100  Wireless system 
           200 ,  300 ,  400 ,  500  Wireless device 
           210 ,  310  Processing section for the A system 
           220 ,  320  Processing section for the B system 
           410 - 1 ,  410 - 2  Antenna 
           420 - 1 ,  510 - 1  Reception processing section for the A system 
           420 - 2 ,  510 - 2  Reception processing section for the B system 
           430 - 1 ,  430 - 2  High-frequency circuit 
           431 - 1 ,  431 - 2  Orthogonal demodulation section 
           432 - 1 ,  432 - 2  Variable gain section 
           433 - 1 ,  433 - 2  AD conversion section 
           440 - 1 ,  440 - 2  Demodulation section 
           450 - 1 ,  450 - 2 ,  520 - 1 ,  520 - 2  Gain control section 
           451 - 1 ,  451 - 2  IQ power measurement section 
           452 - 1 ,  452 - 2  Initial gain storage section 
           453 - 1 ,  453 - 2  Adjustment section 
           454 - 1 ,  454 - 2  Coarse adjustment section 
           455 - 1 ,  455 - 2  Fine adjustment section 
           456  Selection section 
           460 ,  530  Initial gain setting section 
           521 - 1 ,  521 - 2  Received power estimation section