Abstract:
Provided are a time division receiver and a time division receiving method capable of mitigating leaks between branches for a time division multiplexed signal for which a plurality of branches have been time-division multiplexed even when processing using a single high-frequency circuit. In a time division receiver ( 100 A), mixers ( 120 - 1  and  120 - 2 ) down-convert a time division multiplexed signal for which a plurality of branch signals have been time-division multiplexed. Time division separation units ( 130 - 1  and  130 - 2 ) separate the time division multiplexed signal which has been down-converted at the mixers ( 120 - 1  and  120 - 2 ) into branches, respectively. A residual charge initialization unit ( 160 ) initializes charges that are residual when a first branch signal passes for parasitic capacitances that occur in channels between the mixers ( 120 - 1  and  120 - 2 ) and the time division separation units ( 130 - 1  and  130 - 2 ) to the residual charges before passing of a second branch signal.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a time-division receiver and a time-division receiving method for performing processing for receiving a time-division multiplexed signal. 
       BACKGROUND ART 
       [0002]    In recent years, the MIMO (multiple-input and multiple-output) technique has been established and the MIMO technique has been used in many wireless communication standards. In order to practice the MIMO technique, a plurality of radio-frequency circuits are required. Accordingly, the circuit size or power consumption increases as the number of radio-frequency circuits is increased. Therefore, in order to suppress the increase cult size or power consumption, there arises a need to provide a time-division system that can perform processing for a plurality of branches (also referred to as streams) by time-division use of one radio-frequency circuit. 
         [0003]    Patent Literature 1 and Patent Literature 2 each disclose a technique that time-divisionally uses an RF (radio frequency) circuit. Patent Literature 1 discloses an RF circuit for time-division receiver including a mixer. Also Patent Literature 2 discloses a technique for a direct sampling mixer (DSM). 
         [0004]    It has been found that where a time-division receiver, which is represented by the above techniques, is used in a MIMO system, leakage between branches largely affects the reception characteristics of the MIMO system. Therefore, in order to prevent deterioration in reception characteristics, it is necessary to reduce leakage between branches in the time-division receiver as much as possible in the MIMO system. Leakage between branches refers to mixing of signals between the branches. Leakage between branches occurs where a time-divisionally used radio-frequency circuit includes an element having frequency response in a time-division receiver. 
         [0005]    Frequency response is provided by parasitic capacitances. Therefore, ideally, if no parasitic capacitances are generated in the radio-frequency circuit, neither frequency response is provided nor leakage between the branches occurs. 
       CITATION LIST 
     Patent Literature 
     PTL 1 
       [0000]    
       
         Japanese Patent Application Laid-Open No. 2006-135814 
       
     
       PTL 2 
       [0000]    
       
         U.S. Patent Publication No. 2003/35499 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0008]    However, parasitic capacitances exist in an actual element included in a radio-frequency circuit and it is very difficult to completely eliminate the frequency response. Therefore, if an element including parasitic capacitances is shared between branches, signal components before branch switching are accumulated in the parasitic capacitance as a charge, and the accumulated charge exerts influence after the branch switching. Consequently, in the time-division receiver, leakage between the branches occurs, causing the problem of making MIMO decode processing difficult, resulting in deterioration in reception characteristics of the MIMO system. It is known that the problem is more prominent if the time-division receiver is employed in a high-speed broadband wireless transmission system. Therefore, in order to provide a high-speed time-division receiver, mitigation of leakage between branches can be considered an essential technique. 
         [0009]    An object of the present invention is to provide a time-division receiver and a time-division receiving method that even where a time-division multiplexed signal resulting from time-division multiplexing of a plurality of branches is processed by one radio-frequency circuit, can reduce leakage between the branches. 
       Solution to Problem 
       [0010]    A time-division receiver according to one aspect of the present invention employs a configuration including: a mixer that down-converts a tune-division multiplexed signal resulting from a plurality of branch signals being time-division multiplexed; a demultiplexing section that demultiplexes the time-division multiplexed signal down-converted by the mixer, into respective branch signals; and an initializing section that initializes a charge remaining ire a parasitic capacitance, the parasitic capacitance being generated on a path between the mixer and the demultiplexing section, when a first branch signal has passed through the path, before a second branch signal passes through the path. 
         [0011]    A time-division receiving method according to another aspect of the present invention includes: down-converting a time-division multiplexed signal resulting from a plurality of branch signals being time-division multiplexed; demultiplexing the time-division multiplexed signal that has been down-converted into respective branch signals; and initializing a charge remaining in a parasitic capacitance, the parasitic capacitance being generated on a path through which the down-converted time-division multiplexed signal passes, when a first branch signal has passed through the path, before a second branch signal passes through the path. 
       Advantageous Effects of Invention 
       [0012]    According to the present invention, even where time-division multiplexed signal resulting from time-division multiplexing of a plurality of branches is processed by one radio-frequency circuit, leakage between the branches can be reduced. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is a block diagram illustrating a configuration of a time-division receiver to which the present invention is applied; 
           [0014]      FIG. 2  is a diagram illustrating control signals supplied from a control signal generating circuit; 
           [0015]      FIG. 3  is a block diagram illustrating a configuration of a time-division receiver according to embodiment of the presort invention; 
           [0016]      FIG. 4  is a diagram illustrating control signals supplied from a control signal generating circuit; 
           [0017]      FIG. 5  is a diagram conceptually illustrating parasitic capacitances generated on time-division shared signal lines; 
           [0018]      FIG. 6  is a diagram illustrating an internal configuration of a residual charge initializing section according to embodiment 1. 
           [0019]      FIG. 7  is a diagram illustrating a charge in a parasitic capacitance in each of a normal-phase circuit and reversed-phase circuit; 
           [0020]      FIG. 8  is a diagram illustrating a charge remaining in each parasitic capacitances in a time-division receiver according to embodiment 1; 
           [0021]      FIG. 9  is a diagram illustrating a charge remaining in each of parasitic capacitances in a time-division receiver to which the present invention is applied; 
           [0022]      FIG. 10  is a block diagram illustrating another configuration of a time-division receiver according to embodiment 1; 
           [0023]      FIG. 11  is a block diagram illustrating still another configuration of a time-division receiver according to embodiment 1; 
           [0024]      FIG. 12  is a block diagram illustrating still another configuration of a time-division receiver according to embodiment 1; 
           [0025]      FIG. 13  is a block diagram illustrating still another configuration of a time-division receiver according to embodiment 1; 
           [0026]      FIG. 14  is a block diagram illustrating a configuration of a time-division receiver according to embodiment 2 of the present invention; 
           [0027]      FIG. 15  is a diagram conceptually illustrating parasitic capacitances generated on time-division shared signal lines; 
           [0028]      FIG. 16  is a diagram illustrating an internal configuration of a residual charge initializing section according to embodiment 2; 
           [0029]      FIG. 17  is a block diagram illustrating a configuration of a time-division receiver to which the present invention is applied; 
           [0030]      FIG. 18  is a diagram illustrating control signals supplied from a control signal generating circuit; 
           [0031]      FIG. 19  is a diagram illustrating an internal configuration of an SCF; 
           [0032]      FIG. 20  is a block diagram illustrating a configuration of a time-division receiver according to embodiment 3 of the present invention; 
           [0033]      FIG. 21  is a diagram illustrating control signals supplied from a control signal generating circuit; 
           [0034]      FIG. 22  is a diagram conceptually illustrating parasitic capacitances generated on time-division shared signal lines; 
           [0035]      FIG. 23  is a block diagram illustrating another configuration of a time-division receiver according to embodiment 3; 
           [0036]      FIG. 24  is a block diagram illustrating still another configuration of a time-division receiver according to embodiment 3; 
           [0037]      FIG. 25  is a block diagram illustrating still another configuration of a time-division receiver according to embodiment 3; 
           [0038]      FIG. 26  is a block diagram illustrating still another configuration of a time-division receiver according to embodiment 3; 
           [0039]      FIG. 27  is a block diagram illustrating a configuration of a time-division receiver according to embodiment 4 of the present invention; 
           [0040]      FIG. 28  is a block diagram illustrating a configuration of a time-division receiver to which the present invention is applied; 
           [0041]      FIG. 29  is a block diagram illustrating a configuration of a time-division receiver according to embodiment 5 of the present invention; 
           [0042]      FIG. 30  includes diagrams each illustrating spectra of a desired signal and an aliasing signal; 
           [0043]      FIG. 31  is a block diagram illustrating another configuration of a time-division receiver according to embodiment 5; 
           [0044]      FIG. 32  is a block diagram illustrating still another configuration of a time-division receiver according to embodiment 5; 
           [0045]      FIG. 33  is a block diagram illustrating still another configuration of a time-division receiver according to embodiment 5; 
           [0046]      FIG. 34  is a block diagram illustrating still another configuration of a time-division receiver according to embodiment 5; 
           [0047]      FIG. 35  is a block diagram illustrating still a other configuration of a time-division receiver according to embodiment 5; and 
           [0048]      FIG. 36  is a diagram illustrating an example of control signals where the branch count is three. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0049]    Embodiments of the present invention will be described in detail below with reference to the drawings. 
       Embodiment 1 
       [0050]      FIG. 1  is a block diagram illustrating configuration of a time-division receiver to which the present invention is applied. Time-division receiver  100  in  FIG. 1  employs a configuration with the branch count of two which a first branch and a second branch are time-division multiplexed into a single system. 
         [0051]    In  FIG. 1 , time-division receiver  100  includes time-division multiplexing section  110 , mixer  120 , time-division demultiplexing section  130  and control signal generating cult  140 . 
         [0052]    Control signal generating circuit  140  supplies control signals (clocks) to time-division multiplexing section  110  and time-division demultiplexing section  130 . More specifically, control signal generating circuit  140  generates SW 1  and SW 2 , and supplies SW 1  and SW 2  to time-division multiplexing section  110  and time-division demultiplexing section  130 .  FIG. 2  is a diagram illustrating control signals SW 1  and SW 2  supplied from control signal generating circuit  140 . 
         [0053]    Control signal generating circuit  140  also generates local signal LO P . Then, control signal generating circuit  140  supplies local signal Lo p  to mixer  120 . 
         [0054]    Time-division multiplexing section  110  includes input terminals  111  and  112 . A radio-frequency signal for a first branch is input to input terminal  111 . Also, a radio-frequency signal for a second branch is input to input terminal.  112 . 
         [0055]    Time-division multiplexing section  110  time-division multiplexes the radio-frequency signals for the first and second branches in response to SW 1  and SW 2  to generate a single time-division multiplexed signal. More specifically, time-division multiplexing section  110  outputs the radio-frequency signal for the first branch, which has been input from input terminal  111 , to mixer  120  during a period in which SW 1  is active. Also, time-division multiplexing section  110  outputs the radio-frequency signal for the second branch, which has been input from input terminal  112 , to mixer  120  during a period in which SW 2  is active. Here, a branch switching rate needs to be a rate equal to or exceeding a symbol rate for each of the radio-frequency signals. As described above, time-division multiplexing section  110  generates a time-division multiplexed signal and outputs the time-division multiplexed signal to mixer  120 . 
         [0056]    Mixer  120  performs frequency conversion (down-conversion) of the time-division multiplexed signal using local signal Lo p  to generate a baseband time-division multiplexed signal (hereinafter abbreviated, as baseband signal) and outputs the baseband signal to time-division demultiplexing section  130 . 
         [0057]    Time-division demultiplexing section  130  includes output terminals  131  and  132 . Then, time-division demultiplexing section  130  demultiplexes the baseband signal into first and second branches in response to SW 1  and SW 2 . More specifically, time-division demultiplexing section  130  outputs the baseband signal to output terminal  131  during a period in which SW 1  is active. Time-division demultiplexing section  130  also outputs the baseband signal to output terminal  132  during a period in which SW 2  is active. As described above, time-division demultiplexing section  130  demultiplexes the baseband signal into the first and second branches at a branch switching rate equal to that of time-division multiplexing section  110 . 
         [0058]    A configuration of time-division receiver  100  to which the present invention is applied has been described above. Next, a time-division receiver according to the present embodiment will be described. 
         [0059]      FIG. 3  is a block diagram illustrating a configuration of time-division receiver  100 A according to the present embodiment. In  FIG. 3 , components that are the same as those in  FIG. 1  are provided with reference numerals that are the same as those in  FIG. 1  and a description thereof will be omitted. 
         [0060]    In  FIG. 3 , time-division receiver  100 A includes time-division multiplexing section  110 , mixers  120 - 1  and  120 - 2 , time-division demultiplexing sections  130 - 1  and  130 - 2 , control signal generating circuit  140 A, reversed-phase signal generating section  150 , and residual charge initializing section  160 . 
         [0061]    In  FIG. 3 , mixer  120 - 1  and time-division demultiplexing section  130 - 1  process a normal-phase signal in a differential system. Also, mixer  120 - 2  and time-division demultiplexing section  130 - 2  process a reversed-phase signal in the differential system. Hereinafter, processing sections that process normal-phase signal are collectively referred to as a normal-phase circuit, and processing sections that process a reversed-phase signal are collectively referred to as a reversed-phase circuit. 
         [0062]    Furthermore, in  FIG. 3 , a path between time-division multiplexing section  110  and mixer  120 - 1  and a path between reversed-phase signal generating section  150  and mixer  120 - 2  are referred to as time-division shared signal lines  170 - 1  and  170 - 2 , respectively. Also, a path between mixer  120 - 1  and time-division demultiplexing section  130 - 1  (output path for mixer  120 - 1 ) is referred to as time-division shared signal line  180 - 1 . Also, a path between mixer  120 - 2  and time-division demultiplexing section  130 - 2  (output path for mixer  120 - 2 ) is referred to as time-division shared signal line  180 - 2 . 
         [0063]    Control signal generating circuit  140 A supplies control signals to time-division multiplexing section  110 , time division demultiplexing sections  130 - 1  and  130 - 2 , and residual charge initializing section  160 . More specifically, control signal generating circuit  140 A generates control signals SW 1 , SW 2  and SWc. Then, control signal generating circuit  140 A supplies SW 1  and SW 2  to time-division multiplexing section  110  and time-division demultiplexing sections  130 - 1  and  130 - 2 . Control signal generating circuit  140 A also supplies SWc to residual charge initializing section  160 . Furthermore, control signal generating circuit.  140 A generates local signal Lo p  and supplies local signal Lo p  to mixers  120 - 1  and  120 - 2 .  FIG. 4  is a diagram illustrating control signals SW 1 , SW 2  and SWc supplied from control signal generating circuit  140 A. Details of SW 1 , SW 2  and SWc will be described later. 
         [0064]    Control signal generating circuit  140 E generates local signal LO p . Then, control signal generating circuit  140 A supplies local signal LO p  to mixers  120 - 1  and  120 - 2 . 
         [0065]    Time-division multiplexing section  110  time-division multiplexes radio-frequency signals for the first and second branches in response to SW 1  and SW 2  to generate a single time-division multiplexed signal. More specifically, during a period in which SW 1  is active, time-division multiplexing section  110  outputs the radio-frequency signal for the first branch to mixer  120 - 1  and reversed-phase signal generating section  150 . Also, during a period in which SW 2  is active, time-division multiplexing section  110  outputs the radio-frequency signal for the second branch to mixer  120 - 1  and reversed-phase signal generating section  150 . During a period in which neither SW 1  nor SW 2  is active (that is, a period in which SWc is active), time-division multiplexing section  110  provides no output to mixer  120 - 1  and reversed-phase signal generating section  150 . 
         [0066]    Reversed-phase signal generating section  150  reverses a phase of the time-division multiplexed signal to generate a reversed-phase time-division multiplexed signal and outputs the reversed-phase time-division multiplexed signal to mixer  120 - 2 . 
         [0067]    As with mixer  120 , mixers  120 - 1  and  120 - 2  perform frequency conversion (down-conversion) of the respective time-division multiplexed signals using local signal LO p  to generate a baseband time-division multiplexed signal (baseband signal). More specifically, mixer  120 - 1  down-converts the normal-phase time-division multiplexed signal to generate a normal-phase baseband signal. Also, mixer  120 - 2  down-converts the reversed-phase time-division multiplexed signal to generate a reversed-phase baseband signal. The normal-phase baseband signal is output to time-division demultiplexing section  130 - 1  via time-division shared signal line  180 - 1 . The reversed-phase baseband signal is output to time-division demultiplexing section  130 - 2  via time-division shared signal line  180 - 2 . 
         [0068]    As with time-division demultiplexing section  130 , each of time-division demultiplexing sections  130 - 1  and  130 - 2  includes output terminals  131  and  132 . Time-division demultiplexing sections  130 - 1  and  130 - 2  each demultiplex the respective baseband signals into the first and second branches in response to SW 1  and SW 2 . More specifically, demultiplexing sections  130 - 1  and  130 - 2  output the respective baseband signals to respective output terminals  131  during a period in which SW 1  is active. Also, time-division demultiplexing sections  130 - 1  and  130 - 2  output the respective baseband signals to respective output terminals  132  during period in which SW 2  is active. As described above, time-division demultiplexing sections  130 - 1  and  130 - 2  demultiplex the respective time-division multiplexed signals into the first and second branches at a branch switching rate equal to that of time-division multiplexing section  110 . 
         [0069]    Residual charge initializing section  160  initializes charges remaining in parasitic capacitances in time-division receiver  100 A. 
         [0070]    Here, parasitic capacitances generated in time-division receiver  100 A will be described. As described above, time-division shared signal lines  170 - 1  and  170 - 2 , mixers  120 - 1  and  120 - 2  and time-division shared signal lines  180 - 1  and  180 - 2  are shared between the first and second branches. Time-division shared signal lines  170 - 1  and  170 - 2 , mixers  120 - 1  and  120 - 2  and time-division shared signal lines  180 - 1  and  180 - 2  shared between the first and second branches are referred to as time-division shared sections below. 
         [0071]    If an element having frequency response exists in a time-division shared section, as described above, a parasitic capacitance is generated in the element and leakage between branches increases due to the generated parasitic capacitance. Here, from among the time-division shared sections, elements having frequency response, that is, elements in which a parasitic capacitance is generated will be discussed. 
         [0072]    To be exact, time-division shared signal lines  170 - 1 ,  170 - 2 , mixers  120 - 1  and  120 - 2 , and time-division shared signal lines  180 - 1  and  180 - 2  all have frequency response. However, there is a large difference between an LO (local) frequency used by mixers  120 - 1  and  120 - 2  for down-conversion and the branch switching rate. For example, the LO frequency is around 2 GHz while the branch switching rate is around 100 MHz. In other words, in time-division receiver  100 A, mixers  120 - 1  and  120 - 2  can be considered as mere elements for frequency shifting from a first frequency to a second frequency. Then, the branch switching rate is extremely slow compared to the LO frequency, and thus, the frequency response of mixers  120 - 1  and  120 - 2  can be ignored. In other words, parasitic capacitances in mixers  120 - 1  and  120 - 2  can be ignored. Furthermore, since each of the first and second branch signals passing through time-division shared signal lines  170 - 1  and  170 - 2  has a radio frequency, as with mixers  120 - 1  and  120 - 2 , the frequency response of time-division shared signal lines  170 - 1  and  170 - 2  can be ignored. 
         [0073]    Meanwhile, the down-converted baseband signals pass through time-division shared signal lines  180 - 1  and  180 - 2 . Each of the baseband signals has a low frequency, for example, around 5 MHz. Therefore, the frequency of the baseband signals is close to the branch switching rate compared to that of the radio-frequency signals, and thus, the frequency response of time-division shared signal lines  180 - 1  and  180 - 2  should be taken into consideration. Thus, on time-division shared signal lines  180 - 1  and  180 - 2 , parasitic capacitances can be generated. 
         [0074]      FIG. 5  is a diagram conceptually illustrating parasitic capacitances generated on time-division shared signal lines  180 - 1  and  180 - 2 . In  FIG. 5 , parasitic capacitances  190 - 1  and  190 - 2  are parasitic capacitances generated on time-division shared signal lines  180 - 1  and  180 - 2 . In parasitic capacitances  190 - 1  and  190 - 2 , signal components before branch switching remain. 
         [0075]    Therefore, in the present embodiment, in time-division receiver  100 A, residual charge initializing section  160  is connected to time-division shared signal lines  180 - 1  and  180 - 2  (output paths for mixers  120 - 1  and  120 - 2 ). In the present embodiment, residual charge initializing section  160  is configured to initialize charges remaining in parasitic capacitances  190 - 1  and  190 - 2  (hereinafter also referred to as residual charges). 
         [0076]      FIG. 6  is a diagram illustrating an internal configuration of residual charge initializing section  160  and connection to the same. 
         [0077]    Residual charge initializing section  160  includes switch  161 . 
         [0078]    One of connection destinations of switch  161  is the output path for mixer  120 - 1  in the normal-phase circuit and the other is the output path for mixer  120 - 2  in the reversed-phase circuit. 
         [0079]    Then, switch  161  is turned on/off in response to SWc, and consequently, the normal-phase circuit and the reversed-phase circuit are in a conducting or non-conducting state. More specifically, during a period in which SWc is active, switch  161  is on, whereby the normal-phase circuit and the reversed-phase circuit are in a conducting state. Also, during a period in which SWc, is non-active, switch  161  is off, whereby the normal-phase circuit and the reversed-phase circuit are its a non-conducting state. 
         [0080]    Next, the control signals output from control signal generating circuit  140 A will be described with reference to  FIG. 4 . 
         [0081]    In  FIG. 4 , SW 1  is a control signal for time-division multiplexing section  110  and time-division demultiplexing sections  130 - 1  and  130 - 2  to select the first branch. Also, SW 2  is a control signal for time-division multiplexing section  110  and time-division demultiplexing sections  130 - 1  and  130 - 2  to select the second branch. 
         [0082]    As described above, SW 1  and SW 2  for switching between the first and second branches are control signals common to time-division multiplexing section  110  and time-division demultiplexing sections  130 - 1  and  130 - 2 . SW 1  and SW 2  each have a rate higher than the symbol rate. 
         [0083]    Furthermore, as illustrated in  FIG. 4 , SW 1  and SW 2  are not active simultaneously, and there are periods in which both SW 1  and SW 2  are non-active. Each of the periods in which both SW 1  and SW 2  are non-active is a period in which the time-division multiplexed signal is quiescent. Also, each of the periods in which both SW 1  and SW 2  are non-active and the time-division multiplexed signal is quiescent (hereinafter referred to as “quiescent period”) is a period in which SWc is active. Residual charge initializing section  160  initializes the charges accumulated in parasitic capacitances  190 - 1  and  190 - 2  (residual charges) during a period in which SWc is active, that is, a quiescent period. 
         [0084]    Time necessary for initializing the residual charges should be assigned to the period in which SWc is active. However, majority of charge is moved to a parasitic capacitance in an early period in which charge accumulation has started. Therefore, even where residual charges are initialized for residual charge reduction during a period shorter than a period of time consumed for actual accumulation of the residual charges, the initialization of the residual charges can provide an effect of reduction in leakage between the branches. Accordingly, the period in which SWc is active may be shorter than time required to completely initialize the residual charges. 
         [0085]    Furthermore, since each of the periods in which SWc is active is a period in which both SW 1  and SW 2  are non-active (quiescent period), if the period in which SWc is active is long, the period in which SW 1  or SW 2  is active is short. Shortening the period in which SW 1  or SW 2  is active causes deterioration in pass gain characteristic of the signal for the branch for which the active period has been shortened. Meanwhile, shortening the period in which SWc is active disables sufficient initialization of the residual charges, resulting in deterioration in characteristic of leakage between the branches. Therefore, it is necessary to determine the period in which SWc is active taking a trade-off between the pass gain characteristic and the characteristic of leakage between the branches into consideration. 
         [0086]    Next, an operation of residual charge initializing section  160  will be described. 
         [0087]      FIG. 7  is a diagram illustrating charges (residual charges) generally accumulated in a parasitic capacitance in a normal-phase circuit and a parasitic capacitance in a reversed-phase circuit in a differential system. As can be seen from  FIG. 7 , residual charges in the normal-phase circuit and the reversed-phase circuit exhibit symmetry. Thus, the normal-phase circuit and the reversed-phase circuit are in a conducting state, whereby the residual charges in the normal-phase circuit and the reversed-phase circuit are cancelled out. 
         [0088]      FIG. 8  is a diagram illustrating charges (residual charges) accumulated in parasitic capacitances  190 - 1  and  190 - 2  in time-division receiver  100 A according to the present embodiment. 
         [0089]    Residual charge initializing section  160  initializes the residual charges during a period in which SWc is active. More specifically, during the period in which SWc is active, switch  161  is on, whereby the normal-phase circuit and the reversed-phase circuit are in a conducting state (interdifferential short-circuiting). As a result, charges accumulated in parasitic capacitances  190 - 1  and  190 - 2  (residual charges) are cancelled out, whereby the residual charges are initialized. 
         [0090]    As described above, an SWc active period is provided between an SW 1  active period and an SW 2  active period. In the SWc active period, interdifferential short-circuiting is performed. Consequently, in time-division receiver  100 A, after initialization of the charges accumulated in parasitic capacitances  190 - 1 ,  190 - 2  (residual charges), respective signals after branch switching pass through time-division shared signal lines  180 - 1  and  180 - 2 . Thus, time-division receiver  100 A can avoid mixing of signals before branch switching and signals after the branch switching, enabling reduction in leakage between the branches. Consequently, time-division receiver  100 A enables suppression of deterioration MIMO reception characteristics. 
         [0091]    Meanwhile,  FIG. 9  is a diagram illustrating charges accumulated in parasitic capacitances (residual charges) in the normal-phase circuit and the reversed-phase circuit in time-division receiver  100  in  FIG. 1 . In other words,  FIG. 9  illustrates an example where the residual charges are not initialized. In  FIG. 9 , solid lines indicate residual charges before and after branch switching in time-division receiver  100 . In  FIG. 9 , dotted lines indicate residual charges after branch switching in the case of an ideal time-division receiver in which the time-division shared sections of time-division receiver  100  have no frequency response. 
         [0092]    In time-division receiver  100 , after switching from the first branch to the second branch, the signal for the second branch is input with signal components for the first branch remaining in the parasitic capacitances. Therefore, as indicated by the solid lines in  FIG. 9 , the residual charges are large after the branch switching, which indicate that signal components for the first and second branches are mixed. 
         [0093]    As described above, from comparison between  FIG. 8  and  FIG. 9 , time-division receiver  100 A according to the present embodiment can reduce leakage between the branches and can suppress deterioration in MIMO reception characteristics. 
         [0094]    As described above, residual charge section  160  initializes residual charges generated on paths through which time-division multiplexed signals pass, for each branch switching. More specifically, time-division receiver  100 A makes residual charges generated on the paths through which respective time-division multiplexed signals pass, be cancelled out between the differential circuits in the differential system. In residual charge initializing section  160 , in a period in which SWc is active, that is, a quiescent period, switch  161  connects the output path for mixer  120 - 1  and the output path for mixer  120 - 2 . Consequently, time-division receiver  100 A makes a charge remaining in the parasitic capacitance  190 - 1  in the normal-phase circuit and a charge remaining in parasitic capacitance  190 - 2  in the reversed-phase circuit be cancelled out. As described above, residual charge initializing section  160  initializes charges remaining in the respective parasitic capacitances, which are generated on the respective output paths, when respective first branch signals have passed the respective paths, before respective second branch signals pass the respective paths. Consequently, time-division receiver  100 A can reduce leakage between the branches. 
         [0095]    In general, in a differential system, a normal-phase circuit and a reversed-phase circuit basically exhibit symmetry, but do not necessarily exhibit perfect symmetry to be exact. Thus, time-division receiver  100 A does not necessarily completely initialize residual charges. However, even where a normal-phase circuit and a reversed-phase circuit do not exhibit perfect symmetry, time-division receiver  100 A can provide an effect of mitigating leakage between the branches with an extremely simple configuration. 
         [0096]      FIG. 10  is a block diagram illustrating another configuration of a time-division receiver according to the present embodiment. In  FIG. 10 , components that are the same as those in  FIG. 3  are provided with reference numerals that are the same as those in  FIG. 3  and a description thereof will be omitted. Time-division receiver  100 A in  FIG. 3  includes reversed-phase signal generating section  150  in the following stage of time-division multiplexing section  110 . Meanwhile, time-division receiver  100 B in  FIG. 10  includes reversed-phase signal generating sections  150 - 1  and  150 - 2  in the preceding stage of time-division multiplexing sections  110 - 1  and  110 - 2 . Operations of time-division multiplexing sections  110 - 1  and  110 - 2  and reversed-phase, signal generating sections  150 - 1  and  150 - 2  are similar to those of time-division multiplexing section  110  and reversed-phase signal generating section  150 , respectively, and thus, a description thereof will be omitted. 
         [0097]      FIG. 11  is a block diagram illustrating still another configuration of a time-division receiver according to the present embodiment. In  FIG. 11 , components that are the same as those in  FIG. 3  are provided with reference numerals that are the same as those in  FIG. 3  and a description, thereof will be omitted. Time-division receiver  100 C in  FIG. 11  employs a configuration of time-division receiver  100 A in  FIG. 3  with control signal generating circuit  140 B provided instead of control signal generating circuit  140 A and with reversed-phase signal generating section  150  removed. 
         [0098]    As with control signal generating circuit  140 A, control signal generating circuit  140 B generates control signals SW 1  SW 2  and SWc and local signal LO P . Furthermore, control signal generating circuit  140 B generates local signal LO N  obtained by reversing a phase of local signal LO p  and supplies local signal LO N  to mixer  120 - 2 . Consequently, a reversed-phase baseband signal is output from mixer  120 - 2 . 
         [0099]      FIG. 12  is a block diagram illustrating still another configuration of a time-division receiver according to the present embodiment. In  FIG. 12 , components that are the same as those in  FIG. 10  are provided with reference numerals that are the same as those in  FIG. 10  and a description thereof will be omitted. Time-division receiver  100 D in  FIG. 12  employs a configuration of time-division receiver  100 B in  FIG. 10  with reversed-phase signal generating sections  150 - 1  and  150 - 2  removed. Time-division receiver  100 D in  FIG. 12  provides an example configuration where normal-phase signals for first and second branches and reversed-phase signals for the first and second branches are input, respectively. 
         [0100]      FIG. 13  is a block diagram illustrating still another configuration of a time-division receiver according to the present embodiment. In  FIG. 13 , components that are the same as those in  FIG. 10  are provided with reference numerals that are the same as those in  FIG. 10  and a description thereof will be omitted. Time-division receiver  100 E in  FIG. 13  employs a configuration of time-division receiver  100 B in  FIG. 10  with control signal generating circuit  140 B provided instead of control signal generating circuit  140 A and with reversed-phase signal generating sections  150 - 1  and  150 - 2  removed. In time-division receiver  100 E in  FIG. 13 , control signal generating circuit  140 B supplies local signal LO N  obtained by reversing a phase of local signal LO p  to mixer  120 - 2 . Consequently, a reversed-phase baseband signal is output from mixer  120 - 2 . 
         [0101]    The present embodiment has been described in terms of a case where the present invention is applied to time-division receiver  100  in which a time-division shared radio-frequency circuit includes a mixer. However, the configuration of time-division receiver  100  to which the present invention can be applied is not limited to this case. Any types of receivers other than time-division receiver  100  can provide an effect similar to that of time-division receiver  100  by providing residual charge initializing section  160  in the receiver. Such receivers will be described  111  embodiment 3 onwards. 
       Embodiment 2 
       [0102]      FIG. 14  is a block diagram illustrating a configuration of a time-division receiver according to an embodiment of the present invention in  FIG. 14 , components that are the same as those  FIG. 3  are provided with reference numerals that are the same as those in  FIG. 3  and a description thereof will be omitted. Time-division receiver  200  in  FIG. 14  includes residual charge initializing sections  210 - 1  and  210 - 2  instead of residual charge initializing section  160  in time-division receiver  100 A in  FIG. 3 . 
         [0103]      FIG. 15  is a diagram conceptually illustrating parasitic capacitances generated on time-division shared signal lines  180 - 1  and  180 - 2 . In  FIG. 15 , parasitic capacitances  190 - 1  and  190 - 2  are parasitic capacitances generated on time-division shared signal lines  180 - 1  and  180 - 2 . In parasitic capacitances  190 - 1  and  190 - 2 , signal components before branch switching remain. 
         [0104]      FIG. 16  is a diagram illustrating an internal configuration of residual charge initializing section  210 - 1  ( 210 - 2 ) according to the present embodiment and connection to the same. Residual charge initializing section  210 - 1  ( 210 - 2 ) according to the present embodiment includes charge supply section (voltage source)  211  and switch  161 . 
         [0105]    As in embodiment 1, switch  161  is on during a period in which SWc is active, whereby a normal-phase (reversed-phase) circuit and charge supply section  211  are in a conducting state. Also, as in embodiment 1, switch  161  is off during a period in which SWc is non-active, whereby the normal-phase (reversed-phase) circuit and charge supply section  211  are in a non-conducting state. 
         [0106]    In a conducting state, charge supply section  211  supplies charge to parasitic capacitance  190 - 1  ( 190 - 2 ) to bring the charge in parasitic capacitance  190 - 1  ( 190 - 2 ) to a reference charge level. As described above, residual charge initializing section  210 - 1  ( 210 - 2 ) initializes the charge accumulated, in parasitic capacitance  190 - 1  ( 190 - 2 ). 
         [0107]    As described above, residual charge initializing section  210 - 1  ( 210 - 2 ) includes charge supply section  211  and switch  161 . Switch  161  controls connection/disconnection between charge supply section  211  and an output path for mixer  120 - 1  ( 120 - 2 ) for every branch switching. More specifically, switch  161  connects charge supply section  211  and the output path for mixer  120 - 1  ( 120 - 2 ) in a period in which SWc is active, that is, quiescent period. Then, in a conducting state, charge supply section  211  supplies charge to parasitic capacitance  190 - 1  ( 190 - 2 ). As described above, residual charge initializing section  210 - 1  ( 210 - 2 ) initializes a charge remaining in a parasitic capacitance, which is generated on the output path, when a first branch signal has passed through the path, before a second branch signal passes through the path. Consequently, time-division receiver  200  can reduce leakage between the branches. 
         [0108]    Furthermore, in the case where charge supply section  211  is a voltage source that can stably supply charge, time-division receiver  200  can mitigate leakage between the branches with higher precision compared to time-division receivers  100 A and  100 B according to embodiment 1. 
         [0109]    Furthermore, the present embodiment can be applied to non-differential systems as well as differential systems. However, in the case where charge supply section  211  that can stably supply charge is provided, the present embodiment can provide higher performance in mitigating leakage between the branches compared to embodiment 1, but causes a large circuit impact. 
       Embodiment 3 
       [0110]    Embodiments 1 and 2 have been described in terms of a case where the present invention is applied to a time-division receiver in which a radio-frequency circuit includes a mixer. The present embodiment will be described in terms of a case where the present invention is applied to a time-division receiver in which a radio-frequency circuit includes a DSM. 
         [0111]      FIG. 17  is a block diagram illustrating a configuration of a time-division receiver to which the present invention is applied. In  FIG. 17 , components that are the same as those in  FIG. 1  are provided with reference numerals that are the same as those in  FIG. 1  and a description thereof will be omitted. Time-division receiver  300  in  FIG. 17  is a time-division receiver in which a radio-frequency circuit includes a DSM. 
         [0112]    In  FIG. 17 , time-division receiver  300  includes time-division multiplexing section  110 , time-division demultiplexing section  130 , TA (transconductance amplifier: voltage-current converter)  310 , sampler  320 , history capacitor section  330 , SCF (switched capacity filter)  340 , buffer capacitor section  351 ) and control signal generating circuit  360 . 
         [0113]    Control signal generating circuit  360  supplies control signals to time division multiplexing section  110 , time-division demultiplexing section  130 , history capacitor section  330 , SCF  340  and buffer capacitor section  350 . 
         [0114]    More specifically, control signal generating circuit  360  generates control signals SW 11 , SW 12 , SW 21 , SW 22  and S 0  to S 3 . Then, control signal generating circuit  360  supplies SW 11  and SW 12  to time division multiplexing section  110  and history capacitor section  330 . Control signal generating circuit  360  also supplies SW 21  and SW 22  to buffet capacitor section  350  and time-division demultiplexing section  130 . Control signal generating circuit  360  also supplies S 0  to S 3  to SCF  340 .  FIG. 18  is a diagram illustrating control signals SW 1 , SW 12 , SW 21 , SW 22  and S 0  to S 3  supplied from control signal generating circuit  360 . Details of the control signals will be described later. 
         [0115]    Control signal generating circuit  360  also generates local signal LO p . Then, control signal generating circuit  360  supplies local signal LO p  to sampler  320 . 
         [0116]    TA  310  coverts a time-division multiplexed signal from a voltage signal to a current signal, and outputs the time-division multiplexed signal to sampler  320  as an analog RF current signal. 
         [0117]    Sampler  320 , which includes, for example, an FET (field-effect transistor), samples the analog RE current signal using local signal LO p  to perform frequency conversion (down-conversion). 
         [0118]    The signal output from TA  310  and sampler  320  is a current signal, and the current signal is output to time-division demultiplexing section  130 . The subsequent processing is also performed on the current signal. 
         [0119]    History capacitor section  330  includes switches  331  and  333  and Chs (history capacitors)  332  and  334 . 
         [0120]    Switches  331  and  333  are turned on/off in response to SW 11  and SW 12 . More specifically, switch  331  is on during a period in which SW 11  is active and is off during a period in which SW 11  is non-active. Switch  333  is on during a period in which SW 12  is active, and is off during a period in which SW 12  is non-active. 
         [0121]    Ch  332  is a history capacitor for a first branch, and Ch  334  is a history capacitor for a second branch. 
         [0122]    As described above, on an output path for sampler  320 , Ch  332  for the first branch and Ch  334  for the second branch are provided. Connection/disconnection between these capacitors and the output path for sampler  320  are controlled by switches  331  and  333 . 
         [0123]    SCF  340  repeats charging and discharging of later-described rotation capacitors in response to S 0  to S 3  to filter the current signal output from sampler  320 , and outputs the filtered signal to time-division demultiplexing section  130 . A detailed configuration of SCF  340  will be described later. 
         [0124]    Buffer capacitor section  350  includes switches  351  and  353  and Cbs (buffer capacitors)  352  and  354 . 
         [0125]    Switches  351  and  353  are turned on/off in response to SW 21  and SW 22 , respectively. More specifically, switch  351  is on during a period in which SW 21  is active, and is off during a period in which SW 21  is non-active. Switch  353  is on during a period in which SW 22  is active and is off during a period in which SW 22  is non-active. 
         [0126]    Cb  352  is a buffer capacitor for the first branch and Cb  354  is a buffer capacitor for the second branch. 
         [0127]    As described above, on the output path for SCF  340 , Cb  352  for the first branch and Cb  354  for the second branch are provided. Connection/disconnection between these capacitors and the output path for SCF  340  is controlled by switches  351  and  353 . 
         [0128]      FIG. 19  is a diagram illustrating an example detailed configuration inside SCF  340  in  FIG. 17 . 
         [0129]    As illustrated in  FIG. 19 , four paths are provided between an input and an output of SCF  340 . Path  1  includes switches  410 ,  412 ,  413  and  414 , and Cr (rotation capacitor)  411 . Path  2  includes switches  420 ,  422 ,  423  and  424 , and Cr  421 . Path  3  includes switches  430 ,  432 ,  433  and  434 , and Cr  431 . Path  4  includes switches  440 ,  442 ,  443  and  444 , and Cr  441 . Here, switches  410 ,  420 ,  430  and  440  are switches for input control. Switches  412 ,  422 ,  432  and  442  are switches for discharge. Switches  413 ,  423 ,  433  and  443  are switches for pre-charge voltage supply. Switches  414 ,  424 ,  434  and  444  are switches for output control. 
         [0130]    As described above, SCF  340  includes configurations of the four paths, which are completely similar to one another. The respective switches are controlled by S 0  to S 3  supplied from control signal generating circuit  360 . 
         [0131]    Next, an operation of SCF  340  will be described. Each of the four paths in SCF  340  cycles through four states. Since similar processing is performed for the respective paths, description will be provided for path  1 . 
         [0132]    In a first state, switch  412  is turned on, whereby Cr  411  is discharged. 
         [0133]    Next, in a second state, switch  413  is turned on, whereby a pre-charge voltage is supplied to Cr  411  as an initial charge. 
         [0134]    Next, in a third state, switch  410  is turned on, whereby an input signal is loaded, the charge is shared by Cr  411  and history capacitor section  330  in the preceding stage of SCF  340 . 
         [0135]    Lastly, in a fourth state, switch  414  is turned on whereby the charge is shared between Cr  411  and buffer capacitor section  350  in the following stage of SCF  340 . 
         [0136]    For operations in the other paths, processing for the four states is performed in each of the remaining three paths with the state shifted by one state from one another. Then, in the present embodiment, charges are shared by the Chs in history capacitor section  330  and the Crs in SCF  340 , and furthermore charges are shared by the Crs in SCF  340  and the Cbs in buffer capacitor section  350 . Consequently, SCF  340  serves as a second-order IIR (Infinite Impulse Response) filter. 
         [0137]    Here, in  FIG. 18 , SW 11  and SW 12  are control signals supplied to time-division multiplexing section  110 , and switches  331  and  333  in history capacitor section  330 . SW 21  and SW 22  are control signals supplied to time-division demultiplexing section  130 , and switches  351  and  353  in buffer capacitor section  350 . 
         [0138]    During a period in which SW 11  and SW 21  are active, the first branch is selected, and during a period in which SW 12  and SW 22  are active, the second branch is selected. Here, SW 21  and SW 22  are delayed by one time period relative to SW 11  and SW 12  because an input signal is delayed by one time period in SCF  340 . 
         [0139]    A configuration of time-division receiver  300  to which the present invention is applied has been described above. In time-division receiver  300 , a parasitic capacitance is generated on each of an output path for sampler  320  (input path for SCF  340 ) and the output path for SCF  340 . Therefore, in time-division receiver  300 , leakage between the branches occurs due to an influence of charges (residual charges) generated as a result of signal components before branch switching remaining in the parasitic capacitances. Therefore, the present embodiment will be described in terms of a time-division receiver that, where a radio-frequency circuit includes a DSM, can reduce leakage between branches. 
         [0140]      FIG. 20  is a block diagram illustrating a configuration of a time-division receiver  300 A according to the present embodiment. In  FIG. 20 , components that are the same as those in  FIG. 17  are provided with reference numerals that are the same as those in  FIG. 17  and a description thereof will be omitted. 
         [0141]    In  FIG. 20 , time-division receiver  300 A includes time-division multiplexing section  110 , TA  310 , samplers  320 - 1  and  320 - 2 , reversed-phase signal generating section  150 , history capacitor sections  330 - 1  and  330 - 2 , SCFs  340 - 1  and  340 - 2 , buffer capacitor sections  350 - 1  and  350 - 2 , residual charge initializing sections  370 - 1  and  370 - 2 , control signal generating circuit  360 A, and time-division demultiplexing sections  130 - 1  and  130 - 2 . 
         [0142]    In  FIG. 20 , sampler  320 - 1 , history capacitor section  330 - 1 , SCF  340 - 1  and buffer capacitor section  350 - 1  process a normal-phase signal in a differential system. Also, sampler  320 - 2 , history capacitor section  330 - 2 , SCF  340 - 2  and buffer capacitor section  350 - 2  process a reversed-phase signal in the differential system. Hereinafter processing sections that process a normal-phase signal are collectively referred to as a normal-phase circuit, and processing sections that process a reversed-phase signal are collectively referred to as a reversed-phase circuit. 
         [0143]    in  FIG. 20 , a path between sampler  320 - 1  and SCF  340 - 1  (input path for SCF  340 - 1 ) is referred to as time-division shared signal line  390 - 1 . A path between sampler  320 - 2  and SCF  340 - 2  (input path for SCF  340 - 2 ) is referred to as time-division shared signal line  390 - 2 . A path between SCF  340 - 1  and time-division demultiplexing section  130 - 1  (output path for SCF  340 - 1 ) is referred to as time-division shared signal line  390 - 3 . A path between SCF  340 - 2  and time-division demultiplexing section.  130 - 2  (output path for SCF  340 - 2 ) is referred to as time-division shared signal line  390 - 4 . A parasitic capacitance is generated on each of time-division shared signal lines  390 - 1 ,  390 - 2 ,  390 - 3  and  390 - 4 . 
         [0144]    Control signal generating circuit  360 A supplies control signals to time-division multiplexing section  110 , time-division demultiplexing sections  130 - 1  and  130 - 2 , history capacitor sections  330 - and  330 - 2 , SCFs  340 - 1  and  340 - 2 , buffer capacitor sections  350 - 1  and  350 - 2  and residual charge initializing sections  370 - 1  and  370 - 2 . 
         [0145]    More specifically, control signal generating circuit  360 A generates SW 11 , SW 12 , SW 21 , SW 22 , SWc 1 , SWc 2  and S 0  to S 3 . Then, control signal generating circuit  360 A supplies SW 11  and SW 12  to time-division multiplexing section  110  and history capacitor sections  330 - 1  and  330 - 2 . Control signal generating circuit  360 A also supplies SW 21  and SW 22  to buffer capacitor sections  350 - 1  and  350 - 2  and time-division demultiplexing sections  130 - 1  and  130 - 2 . Control signal generating circuit  360 A also supplies SWc 1  to residual charge initializing section  370 - 1 . Control signal generating circuit  360 A also supplies SWc 2  to residual charge initializing section  370 - 2 . Control signal generating circuit  360 A also supplies S 0  to S 3  to SCFs  340 - 1  and  340 - 2 .  FIG. 21  is a diagram illustrating control signals SW 11 , SW 12 , SW 21 , SW 22 , SWc 1 , SWc 2  and S 0  to S 3  supplied from control signal generating circuit  360 A. Details of the control signals will be described later. 
         [0146]    Control signal generating circuit  360 A also generates local signal LO p . Then, control signal generating circuit  360 A supplies local signal LO p  to samplers  320 - 1  and  320 - 2 . 
         [0147]    Reversed-phase signal generating section  150  reverses a phase of a current signal output from TA  310  to generate a reversed-phase time-division multiplexed signal and outputs the reversed-phase time-division multiplexed signal to sampler  320 - 2 . 
         [0148]    As with sampler  320 , samplers  320 - 1  and  320 - 2  sample the analog RF current signal using local signal LO p  to perform frequency conversion (down-con version). 
         [0149]    As with history capacitor section  330 , each of history capacitor sections  330 - 1  and  330 - 2  includes switches  331  and  333 , and Chs  332  and  334 . Switches  331  and  333  switch connection/disconnection between respective output paths for sampler  320 - 1  and  320 - 2  and respective Chs  332  for a first branch or respective Chs  334  for a second branch in response to SW 11  and SW 12 . 
         [0150]    SCFs  340 - 1  and  340 - 2  each employs a configuration similar to that of SCF  340 . SCF  340 - 1  repeats charging/discharging of rotation capacitors in response to S 0  to S 3  to filter the normal-phase current signal, and outputs the filtered signal to time-division demultiplexing section  130 - 1 . Also, SCF  340 - 2  repeats charging/discharging of rotation capacitors in response to S 0  to S 3  to filter the reversed-phase current signal, and outputs the filtered signal to time-division demultiplexing section  130 - 2 . 
         [0151]    As with buffer capacitor section  350 , each of buffer capacitor sections  350 - 1  and  350 - 2  includes switches  351  and  353 , and Cbs  352  and  354 . Switches  351  and  353  switch connection/disconnection between respective output paths for SCFs  340 - 1  and  340 - 2  and Cb  352  for the first branch or Cb  354  for the second branch in response to SW 21  and SW 22 . 
         [0152]    As with time-division demultiplexing section  130 , each of time-division demultiplexing sections  130 - 1  and  130 - 2  demultiplexes a baseband time-division multiplexed signal (baseband signal) into the first and second branches in response to SW 21  and SW 22 . More specifically, time-division demultiplexing sections  130 - 1  and  130 - 2  output the respective baseband signals to respective output terminals  131  during period in which SW 21  is active. Also, time-division demultiplexing sections  130 - 1  and  130 - 2  output the respective baseband signals to respective output terminals  132  during a period in which SW 22  is active. 
         [0153]    Residual charge initializing sections  370 - 1  and  370 - 2  initialize charges remaining in parasitic capacitances in time-division receiver  300 A. 
         [0154]      FIG. 22  is a diagram conceptually illustrating parasitic capacitances generated in time-division receiver  300 A. In  FIG. 22 , parasitic capacitances  380 - 1 ,  380 - 2 ,  380 - 3  and  380 - 4  are parasitic, capacitances generated in time-division receiver  300 A. Signal components before branch switching remain in parasitic capacitances  380 - 1 ,  380 - 2 ,  380 - 3  and  380 - 4 . 
         [0155]    Therefore, in time-division receive  300 A according to the present embodiment, residual charge initializing sections  370 - 1  and  370 - 2  are provided in the preceding and following stages of SCFs  340 - 1  and  340 - 2 , respectively. Here, an internal configuration of residual charge initializing sections  370 - 1  and  370 - 2  is similar to that of residual charge initializing section  160 , and thus, illustration and description thereof will be omitted. 
         [0156]    In other words, in the present embodiment, residual charge initializing section  370 - 1  makes charges accumulated in parasitic capacitances  380 - 1  and  380 - 2  generated in the preceding stage of SCFs  340 - 1  and  340 - 2  (residual charges) be initialized (cancelled out). Also, residual charge initializing section  370 - 2  makes charges accumulated in parasitic capacitances  380 - 3  and  380 - 4  generated in the following stage of SCFs  340 - 1  and  340 - 2  (residual charges) be initialized (cancelled out). 
         [0157]    Next, control signals output from control signal generating circuit  360 A will be described with reference to  FIG. 21 . 
         [0158]    In  FIG. 21 , SW 11  and SW 12  are control signals supplied to time-division multiplexing section  110 , and switches  331  and  333  in history capacitor sections  330 - 1  and  330 - 2 . SW 21  and SW 22  are control signals supplied to time-division demultiplexing sections  130 - 1  and  130 - 2 , and switches  351  and  353  in buffer capacitor sections  350 - 1  and  350 - 2 . SWc 1  and SWc 2  are control signals for controlling respective switches  161  in residual charge initializing sections  370 - 1  and  370 - 2 . During a period in which SWc 1  and SWc 2  are active, switches  161  in residual charge initializing sections  370 - 1  and  370 - 2  are on, whereby a normal-phase circuit and a reversed-phase circuit are in a conducting state (interdifferential short-circuiting). As a result, charges accumulated in the parasitic capacitances in the normal-phase circuit and the reversed-phase circuit (residual charges) are cancelled out, whereby the residual charges are initialized. 
         [0159]    Here, control signals used in the present embodiment (see  FIG. 21 ) and control signals in  FIG. 18  are different from each other in the following points. In the control signals in  FIG. 21 , a non-active period is provided between an SW 11  active period and an SW 12  active period, and between an SW 21  active period and an SW 22  active period. Meanwhile, in the control signals in  FIG. 18 , there is no non-active period between an SW 11  active period and an SW 12  active period, and between an SW 21  active period and an SW 22  active period. 
         [0160]    SWc 1  is active only during a period in which SW 11  and SW 12  are non-active. SWc 2  is active only during a period in which SW 21  and SW 22  are non-active. Here, as mentioned in embodiment 1, the periods in which SWc 1  and SWc 2  are active are determined taking a trade-off between the pass gain characteristic and the characteristic of leakage between the branches into consideration. 
         [0161]    Although the above description has been provided in terms of a case where time-division receiver  300 A includes residual charge initializing sections  370 - 1  and  370 - 2  in the preceding and following stages of SCFs  340 - 1  and  340 - 2 , respectively, time-division receiver  300 A is not limited to this case. Time-division receiver  300 A can provide the effect of reducing leakage between the branches even if time-division receiver  300 A includes either one of the residual charge initializing sections. 
         [0162]    As described above, residual charge initializing section  370 - 1  is connected to the path between sampler  320 - 1  and SCF  340 - 1  and also to the path between sampler  320 - 2  and SCF  340 - 2 . Residual charge initializing section  370 - 1  connects the paths during a period in which SWc 1  is active (quiescent period). Residual charge initializing section  370 - 2  is connected to the path between SCF  340 - 1  and time-division demultiplexing section  130 - 1  and also to the path between SCF  340 - 2  and time-division demultiplexing section  130 - 2 . Residual charge initializing section  370 - 2  connects the paths during a period in which SWc 2  is active (quiescent period). As described above, residual charge initializing sections  370 - 1  and  370 - 2  initialize charges remaining in the parasitic capacitances, which are generated on the paths through which respective time-division multiplexed signals pass, when respective first branch signals have passed through the respective paths, before respective second branch signals pass through the respective paths. Consequently, time-division receiver  300 A can reduce leakage between the branches. 
         [0163]      FIG. 23  is a block diagram illustrating another configuration of a time-division receiver according to the present embodiment. In  FIG. 23 , components that are the same as those in  FIG. 20  are provided with reference numerals that are the same as those in  FIG. 20  and a description thereof will be omitted. Time-division receiver  300 A in  FIG. 20  includes reversed-phase signal generating section  150  in the following stage of time-division multiplexing section  110 . Meanwhile, time-division receiver  300 B in  FIG. 23  includes reversed-phase signal generating sections  150 - 1  and  150 - 2  in the preceding stage of time-division multiplexing sections  110 - 1  and  110 - 2 . Operations of time-division multiplexing sections  110 - 1  and  110 - 2  and reversed-phase signal generating sections  150 - 1  and  150 - 2  are similar to those of time-division multiplexing section  110  and reversed-phase signal generating section  150 , respectively, and thus a description thereof will be omitted. Also, operations of TAs  310 - 1  and  310 - 2  are similar to that of TA  310 , and thus a description thereof will be omitted. 
         [0164]    In time-division receiver  300 B, residual charge initializing section  370 - 1  is connected to a path between sampler  320 - 1  and SCF  340 - 1  and also to a path between sampler  320 - 2  and SCF  340 - 2 . Residual charge initializing section  370 - 1  connects the paths during a period in which SWc 1  is active (quiescent period). Residual charge initializing section  370 - 2  is connected to a path between SCF  340 - 1  and time-division demultiplexing section  130 - 1  and also to a path between SCF  340 - 2  and time-division demultiplexing section  130 - 2 . Residual charge initializing section  370 - 2  connects the paths during a period in which SWc 2  is active (quiescent period). As described above, residual charge initializing sections  370 - 1  and  370 - 2  initialize charges remaining in respective parasitic capacitances, which generated on the respective paths through which respective time-division multiplexed signals pass, when respective first branch signals have passed through the respective paths, before respective second branch signals pass through the respective paths. As a result, time-division receiver  300 B can reduce leakage between the branches. 
         [0165]      FIG. 24  is a block diagram illustrating still another configuration of a time-division receiver according to the present embodiment in  FIG. 24 , components that are the same as those in  FIG. 20  are provided with reference numerals that are the same as those in  FIG. 20  and a description thereof will be omitted. Time-division receiver  300 C in  FIG. 24  employs a configuration of time-division receiver  300 A in  FIG. 20  with control signal generating circuit  360 B provided instead of control signal generating circuit  360 A and with reversed-phase signal generating section  150  removed. 
         [0166]    As with control signal generating circuit  360 A, control signal generating circuit  360 B generates control signals SW 11 , SW 12 , SW 21 , SW 22 , SWc 1 , SWc 2  and S 0  to S 3 , and local signal LO P . Furthermore, control signal generating circuit  360 B generates local signal LO N  obtained by reversing a phase of local signal LO P , and supplies local signal LO N  to sampler  320 - 2 . Consequently, a reversed-phase baseband signal is output from sampler  320 - 2 . 
         [0167]      FIG. 25  is a block diagram illustrating still another configuration of a time-division receiver according to the present embodiment. In  FIG. 25 , components that are the same as those in  FIG. 23  are provided with reference numerals that are the same as those in  FIG. 23  and a description thereof will be omitted. Time-division receiver  300 D in  FIG. 25  employs a configuration of time-division receiver  300 B in  FIG. 23  with reversed-phase signal generating sections  150 - 1  and  150 - 2  to removed. Time-division receiver  300 D in  FIG. 25  provides an example configuration for a case where normal-phase signals for first and second branches and reversed-phase signals for the first and second branches are input, respectively. 
         [0168]      FIG. 26  is a block diagram illustrating still another configuration of a time-division receiver according to the present embodiment. In  FIG. 26 , components that are the same as those in  FIG. 23  are provided with reference numerals that are the same as those in  FIG. 23  and a description thereof will be omitted. Time-division receiver  300 E in  FIG. 26  employs a configuration of time-division receiver  300 B in  FIG. 23  with control signal generating circuit  360 B provided instead of control signal generating circuit  360 A and with reversed-phase signal generating sections  150 - 1  and  150 - 2  removed. In time-division receiver  300 E in  FIG. 26 , control signal generating circuit  360 B supplies local signal LO N  obtained by reversing a phase of local signal LO p  to sampler  320 - 2 . Consequently, a reversed-phase baseband signal is output from sampler  320 - 2 . 
       Embodiment 4 
       [0169]      FIG. 27  is a block diagram illustrating a configuration of a time-division receiver  500  according to the present embodiment. In  FIG. 27 , components that are the same as those in  FIG. 20  are provided with reference numerals that are the same as those in  FIG. 20  and a description thereof will be omitted. Time-division receiver  500  in  FIG. 27  includes residual charge initializing sections  510 - 1 ,  510 - 2 ,  520 - 1  and  520 - 2  instead of residual charge initializing sections  370 - 1  and  370 - 2  in time-division receiver  300 A in  FIG. 20 . 
         [0170]    Each of residual charge initializing sections  510 - 1 ,  510 - 2 ,  520 - 1  and  520 - 2  employs a configuration similar to that of residual charge initializing sections  210 - 1  and  210 - 2  (see  FIG. 16 ), and includes switch  161  and charge supply section  211 . 
         [0171]    In residual charge initializing section  510 - 1  ( 510 - 2 ), switch  161  is on during a period in which SWc 1  is active, whereby a normal-phase (reversed-phase) circuit and charge supply section  211  are in a conducting state. Also, in residual charge initializing section  510 - 1  ( 510 - 2 ), switch  161  is off during a period in which SWc 1  is non-active, whereby the normal-phase (reversed-phase) circuit and charge supply section  211  are in a non-conducting state. 
         [0172]    Also, in residual charge initializing section  520 - 1  ( 520 - 2 ), switch  161  is on dining a period in which SWc 2  is active, whereby the normal-phase (reversed-phase) circuit and charge supply section  211  are in a conducting state. Also, in residual charge initializing section  520 - 1  ( 520 - 2 ), switch  161  is off during a period in which SWc 2  is non-active, whereby the normal-phase (reversed-phase) circuit and charge supply section  211  are in a non-conducting state. 
         [0173]    In a conducting state, charge supply section  211  in each of residual charge initializing sections  510 - 1 ,  510 - 2 ,  520 - 1  and  520 - 2  supplies charge to a parasitic capacitance to bring the charge in the parasitic capacitance to a reference charge level. As described above, residual charge initializing section  510 - 1  ( 510 - 2 ) initializes a residual charge generated on an output path for sampler  320 - 1  ( 320 - 2 ). Residual charge initializing section  520 - 1  ( 520 - 2 ) initializes a residual charge generated on an output path for SCF  340 - 1  ( 340 - 2 ). 
         [0174]    As described above, residual charge initializing section  510 - 1  is connected to a path between sampler  320 - 1  and SCF  340 - 1 . Residual charge initializing section  510 - 1  connects charge supply section  211  and the path during a period in which SWc 1  is active (quiescent period). Residual charge initializing section  520 - 1  is connected to a path between SCF  340 - 1  and time-division demultiplexing section  130 - 1 . Residual charge initializing section  520 - 1  connects charge supply section  211  and the path during a period in which SWc 2  is active (quiescent period). Also, residual charge initializing section  510 - 2  is connected to a path between sampler  320 - 2  and SCF  340 - 2 . Residual charge initializing section  510 - 2  connects charge supply section  211  and the path during a period in which SWc 1  is active (quiescent period). Residual charge initializing section  520 - 2  is connected to a path between SCF  340 - 2  and a time-division demultiplexing section  130 - 2 . Residual charge initializing section  520 - 2  connects charge supply section  211  and the path during a period in which SWc 2  is active (quiescent period). As described above, each of residual charge initializing sections  510 - 1 ,  510 - 2 ,  520 - 1  and  520 - 2  initializes a charge remaining in the respective parasitic capacitance, which is generated on the respective path through which a respective time-division multiplexed signal passes, when a respective first branch signal has passed through the respective path, before a respective second branch signal passes through the respective path. As a result, time-division receiver  500  can reduce leakage between the branches. 
         [0175]    Also, in the case where charge supply section  211  is a voltage source that can stably supply charge, time-division receiver  500  can mitigate leakage between the branches with higher precision compared to time-division receiver  300 A according to embodiment 3. 
         [0176]    Also, the present embodiment can be applied to non-differential systems as well as differential systems. However, in the case where charge supply section  211  that can stably supply charge is provided, the present embodiment can provide higher performance in mitigating leakage between the branches, compared to embodiment 3, but causes a large circuit impact. 
       Embodiment 5 
       [0177]      FIG. 28  is a block diagram illustrating a configuration of a time-division receiver to which the present invention is applied. In  FIG. 28 , components that are the same as those in  FIG. 17  are provided with reference numerals that are the same as those in  FIG. 17  and a description thereof will be omitted. Time-division receiver  600  in  FIG. 28  includes buffer capacitor section  610  instead of buffer capacitor section  350  in time-division receiver  300  in  FIG. 17 . 
         [0178]    In  FIG. 28  tittle-division receiver  600  includes time-division multiplexing section  110 , time-division demultiplexing section  130 , TA  310 , sampler  320 , history capacitor section  330 , SCF  340 , buffer capacitor section  610  and control signal generating circuit  360 . 
         [0179]    Buffer capacitor section  610  includes Cbs  611  and  612 . Meanwhile, buffer capacitor section  350  includes Cbs  352  and  354  and switches  351  and  353 . In other words, buffer capacitor section  610  has a smaller number of parts compared to buffer capacitor section  350  because of lack of switches  351  and  353 . Therefore, time-division receiver  600  can have a reduced circuit size compared to time-divisions receiver  300 . 
         [0180]    Cb  611  is connected to a Cr in SCF  340  during a period in which SW 21  is active. Cb  612  is connected to a Cr in SCF  340  during a period in which SW 22  is active. Consequently, in the present embodiment, IIR filtering is performed for each of first and second branches. 
         [0181]    A configuration of time-division receiver  600  to which the present invention is applied has been described above. 
         [0182]    Next, time-division receiver  600 A according to an embodiment of the present invention will be described. 
         [0183]      FIG. 29  is a block diagram illustrating a configuration of a time-division receiver  600 A according to the present embodiment. In  FIG. 29 , components that are the same as those in  FIG. 28  are provided with reference numerals that are the same as those in  FIG. 28  and a description thereof will be omitted. 
         [0184]    In  FIG. 29 , time-division receiver  600 A includes time-division multiplexing section  110 , TA  310 , samplers  320 - 1  and  320 - 2 , reversed-phase signal generating section  150 , history capacitor sections  330 - 1  and  330 - 2 , SCFs  340 - 1  and  340 - 2 , residual charge initializing sections  370 - 1  and  370 - 2 , control signal generating circuit  360 A, time-division demultiplexing sections  130 - 1  and  130 - 2  and buffer capacitor sections  610 - 1  and  610 - 2 . Here, a configuration and an operation of each of buffer capacitor sections  610 - 1  and  610 - 2  are similar to those of buffer capacitor section  610 , and a description thereof will be omitted. 
         [0185]    Here, differences between time-division receiver  300 A in  FIG. 20  and time-division receiver  600 A in  FIG. 29  will be described. 
         [0186]    In time-division receiver  300 A, during a period in which SW 21  and SW 22  is non-active (that is a period in which SWc 2  is active), no signals are output to output terminals  131  and  132  (zero padding). Therefore, in time-division receiver  300 A, there is a period in which output terminal  131  and output terminal  132  output no signals at all. As a result, an aliasing signal generated in a cycle corresponding to a branch switching rate is output from time-division receiver  300 A. 
         [0187]    In time-division receiver  600 A, during a period in which SW 21  and SW 22  is non-active (that is, a period in which SWc 2  is active), no signals are output to output terminals  131  and  132  as in time-division receiver  300 A. However, Chs  611  and  612  connected to output terminals  131  and  132  retain immediately previous baseband signals for first and second branches, respectively. Therefore, in time-division receiver  600 A, even during a period in which SW 21  and SW 22  is non-active (that is, a period in which SWc 2  is active), signals are output from buffer capacitor sections  610 - 1  and  610 - 2 . As a result, time-division receiver  600 A can suppress aliasing signals. 
         [0188]      FIG. 30  includes diagrams each illustrating spectra of a desired signal and an aliasing signal.  FIG. 30A  is a diagram illustrating spectra of a desired signal and an aliasing signal in time-division receiver  300 A.  FIG. 30B  is a diagram illustrating spectra of a desired signal and an aliasing signal in time-division receiver  600 A. As can be seen from  FIGS. 30A and 30B  time-division receiver  600 A provides a smaller aliasing signal spectrum with reference to a desired signal spectrum compared to time-division receiver  300 A. 
         [0189]    This is because Cbs  611  and  612  in buffer capacitor sections  610 - 1  and  610 - 2  provided in the following stage of time-division demultiplexing sections  130 - 1  and  130 - 2  retain immediately previous branch signal components during a period in which neither first branch signal nor second branch signal is input. 
         [0190]    With the configuration described above, in a Ch connected to a branch for which no signal is output from time-division demultiplexing section  130 - 1  ( 130 - 2 ), from among Cbs  611  and  612 , a charge of immediately previous signal components is retained. Consequently, an output voltage from each of buffer capacitor sections  610 - 1  and  610 - 2  becomes equal to that of a state in which the immediately previous signal components have passed. As a result, time-division receiver  600 A can suppress aliasing signals contained in an output signal, compared to time-division receiver  300 A. Therefore, time-division receiver  600 A enables mitigation of required characteristics of filters that are necessary to be provided in the following stage of time-division receiver  600 A for aliasing signal removal. 
         [0191]    As described above, residual charge initializing section  370 - 1  is connected to a path between sampler  320 - 1  and SCF  340 - 1  and also to a path between sampler  320 - 2  and SCF  340 - 2 . Residual charge initializing section  370 - 1  connects the paths during a period in which SWc 1  is active (quiescent period). Residual charge initializing section  370 - 2  is connected to a path between SCF  340 - 1  and time-division demultiplexing section  130 - 1  and also to a path between SCF  340 - 2  and time-division demultiplexing section  130 - 2 . Residual charge initializing section  370 - 2  connects the paths during a period in which SWc 2  is active (quiescent period). As described above, residual charge initializing sections  370 - 1  and  370 - 2  initialize charges remaining respective parasitic capacitances, which are generated on respective paths through which respective time-division multiplexed signals pass, when respective first branch signals have passed through the respective paths, before respective second branch signals pass through the respective paths. As a result, time-division receiver  600 A can reduce leakage between the branches. 
         [0192]      FIG. 31  is a block diagram illustrating another configuration of a time-division receiver according to the present embodiment in  FIG. 31 , time-division receiver  600 B includes reversed-phase signal generating sections  150 - 1  and  150 - 2 , time-division multiplexing sections  110 - 1  and  110 - 2 , TAs  310 - 1  and  310 - 2 , samplers  320 - 1  and  320 - 2 , history capacitor sections  330 - 1  and  330 - 2 , SCFs  340 - 1  and  340 - 2 , residual charge initializing sections  370 - 1  and  370 - 2 , control signal generating circuit  360 A, time-division demultiplexing sections  130 - 1  and  130 - 2 , and buffer capacitor sections  610 - 1  and  610 - 2 . 
         [0193]    In time-division receiver  600 B, residual charge initializing section  370 - 1  is connected to a path between sampler  320 - 1  and SCF  340 - 1  and also to a path between sampler  320 - 2  and SCF  340 - 2 . Residual charge initializing section  370 - 1  connects the paths during a period in which SWc 1  is active (quiescent period). Residual charge initializing section  370 - 2  is connected to a path between SCF  340 - 1  and time-division demultiplexing section  130 - 1  and also to a path between SCF  340 - 2  and time-division demultiplexing section  130 - 2 . 
         [0194]    Residual charge initializing section  370 - 2  connects the paths in during a period in which SWc 2  is active (quiescent period). As described above, residual charge initializing sections  370 - 1  and  370 - 2  initialize charges remaining in respective parasitic capacitances, which are generated on respective paths through which respective time-division multiplexed signals pass when respective first branch signals have passed through the respective paths before respective second branch signals pass through the respective paths. As a result, time-division receiver  600 B can reduce leakage between the branches. 
         [0195]      FIG. 32  is a block diagram illustrating still another configuration of a time-division receiver according to the present embodiment. In  FIG. 32 , components that are the same as those in  FIG. 29  are provided with reference numerals that are the same as those in  FIG. 29  and a description thereof will be omitted. Time-division receiver  600 C in  FIG. 32  employs a configuration of time-division receiver  600 A in  FIG. 29  with control signal generating circuit  360 B provided instead of control signal generating circuit  360 A and with reversed-phase signal generating section  150  removed. In time-division receiver  600 C in  FIG. 32 , control signal generating circuit  360 B supplies local signal LO N  obtained by reversing a phase of local signal. LO p  to sampler  320 - 2 . Consequently, a reversed-phase baseband signal is output from sampler  320 - 2 . 
         [0196]      FIG. 33  is a block diagram illustrating still another configuration of a time-division receiver according to the present embodiment. In  FIG. 33 , components that are the same as those in  FIG. 31  are provided with reference numerals that are the same as those in  FIG. 31  and a description thereof will be omitted. Time-division receiver  600 B in  FIG. 33  employs a configuration of time-division receiver  600 B in  FIG. 31  with reversed-phase signal generating sections  150 - 1  and  150 - 2  is removed. Time-division receiver  600 D in  FIG. 33  provides an example configuration where normal-phase signals for first and second branches and reversed-phase signal for first and second branches are input, respectively. 
         [0197]      FIG. 34  is a block diagram illustrating still another configuration of a time-division receiver according to the present embodiment. In  FIG. 34 , components that are the same as those in  FIG. 31  are provided, with reference numerals that are the same as those in  FIG. 31  and a description thereof will be omitted. Time-division receiver  600 E in  FIG. 34  employs a configuration of time-division receiver  600 B in  FIG. 31  with control signal generating circuit  360 B provided instead of control signal generating circuit  360 A and with reversed-phase signal generating sections  150 - 1  and  150 - 2  removed. In time-division receiver  600 E in  FIG. 34 , control signal generating circuit  360 B supplies local signal LO N  obtained by reversing a phase of local signal LO p  to sampler  320 - 2 . Consequently, reversed-phase baseband signal is output from sampler  320 - 2 . 
         [0198]      FIG. 35  is a block diagram illustrating still another configuration of a time-division receiver according to the present embodiment in  FIG. 35 , time-division receiver  600 F includes time-division multiplexing section  110 , TA  310 , samplers  320 - 1  and  320 - 2 , reversed-phase signal generating section  150 , history capacitor sections  330 - 1  and  330 - 2 . SCFs  340 - 1  and  340 - 2 , residual charge initializing sections  510 - 1 ,  510 - 2 ,  520 - 1  and  520 - 2 , control signal generating circuit  360 A, time-division demultiplexing sections  130 - 1  and  130 - 2 , and buffer capacitor sections  610 - 1  and  610 - 2 . 
         [0199]    In time-division receiver  600 F, residual charge initializing section  510 - 1  is connected to a path between sampler  320 - 1  and SCF  340 - 1 . Residual charge initializing section  510 - 1  connects charge supply section  211  and the path during a period in which SWc 1  is active (quiescent period). Residual charge initializing section  520 - 1  is connected to a path between SCF  340 - 1  and time-division section  130 - 1 . Residual charge initializing section  520 - 1  connects charge supply section  211  and the path during a period in which SWc 2  is active (quiescent period). Residual charge initializing section  510 - 2  is connected to a path between sampler  320 - 2  and SCF  340 - 2 . Residual charge initializing section  510 - 2  connects charge supply section  211  and the path during a period in which SWc 1  is active (quiescent period). Residual charge initializing section  520 - 2  is connected to a path between SCF  340 - 2  and time-division section  130 - 2 . Residual charge initializing section  520 - 2  connects charge supply section  211  and the path during a period in which SWc 2  is active (quiescent period). As described above, residual charge initializing sections  510 - 1 ,  510 - 2 ,  520 - 1  and  520 - 2  initialize charges remaining in respective parasitic capacitances, which are generated on the respective paths through which respective time-division multiplexed signals pass, when respective first branch signals have passed through the respective paths, before respective second branch signals pass through the paths. As a result, time-division receiver  600 F can reduce leakage between the branches. 
         [0200]    As in time-division receiver  600 A, in time-division receivers  600 B,  600 C,  600 D,  600 E and  600 F, buffer capacitor sections  610 - 1  and  610 - 2  are provided in the following stage of time-division demultiplexing sections  130 - 1  and  130 - 2 , respectively. Therefore, time-division receiver  600 C can mitigate required characteristics of filters in the following stage thereof. 
         [0201]    The respective embodiments have been described above. 
         [0202]    The above description, has been provided taking a case where the branch count is two as an example, but the branch count is not limited to two. The present invention can also be applied to a case where streams with a branch count of three or more are time-division multiplexed.  FIG. 36  is a diagram illustrating an example of respective control signals where the branch count is three. Also in the case where the branch count is three, it is only necessary that a time-division multiplexing section generates a time-division multiplexed signal including quiescent period between the respective branches and a residual charge initializing section initializes a residual charge during the quiescent period. 
         [0203]    The entire disclosure of the description, the drawings and the abstract included in Japanese Patent Application No. 2010-292716 filed on Dec. 28, 2010 is incorporated herein by reference. 
       INDUSTRIAL APPLICABILITY 
       [0204]    A time-division receiver and a time-division receiving method according to the present invention are useful for e.g., a receiver in a MIMO system requiring simultaneous reception of radio-frequency signals for a plurality of branches. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           100 ,  100 A,  100 B,  100 C,  100 D,  100 E,  200 ,  300 ,  300 A,  300 B,  300 C,  300 D,  300 E,  500 ,  600 ,  600 A,  600 B,  600 C,  600 D,  600 E,  600 F Time-division receiver 
           110 ,  110 - 1 ,  110 - 2  Time-division multiplexing section 
           111 ,  112  Input terminal 
           120 ,  120 - 1 ,  120 - 2  Mixer 
           130 ,  130 - 1 ,  130 - 2  Time-division demultiplexing section 
           131 ,  132  Output terminal 
           140 ,  140 A,  140 B,  360 ,  360 A,  360 B Control signal generating circuit 
           150 ,  150 - 1 ,  150 - 2  Reversed-phase signal generating section 
           160 ,  210 - 1 ,  210 - 2 ,  370 - 1 ,  370 - 2 ,  510 - 1 ,  510 - 2 ,  520 - 1 ,  520 - 2  Residual charge initializing section 
           161 ,  331 ,  333 ,  351 ,  353 ,  410 ,  412 ,  413 ,  414 ,  420 ,  422 ,  423 ,  424 ,  430 ,  432 ,  433 ,  434 ,  440 ,  442 ,  443 ,  444  Switch 
           170 - 1 ,  170 - 2 ,  180 - 1 ,  180 - 2 ,  390 - 1 ,  390 - 2 ,  390 - 3 ,  390 - 4  Time-division shared signal line 
           190 - 1 ,  190 - 2 ,  380 - 1 ,  380 - 2 ,  380 - 3 ,  380 - 4  Parasitic capacitance 
           211  charge supply section 
           310 ,  310 - 1 ,  310 - 2  TA 
           320 ,  320 - 1 ,  320 - 2  Sampler 
           330 ,  330 - 1 ,  330 - 2  History capacitor section 
           340 ,  340 - 1 ,  340 - 2  SCF 
           350 ,  350 - 1 ,  350 - 2 ,  510 - 1 ,  510 - 2 ,  610 - 1 ,  610 - 2  Buffer capacitor section 
           332 ,  334  Ch 
           352 ,  354 ,  611 ,  612  Cb 
           411 ,  421 ,  431 ,  441  Cr