Abstract:
A frequency up and down converter, in which, when down converting a high frequency signal into an intermediate frequency signal or up converting an intermediate frequency signal into a high frequency signal by controlling switching elements using a local oscillator signal, a signal with a frequency to be converted is controlled a number of times during one cycle of the local oscillator signal, whereby the local oscillator signal with a frequency lower than an original frequency may be used. Transistors are added in parallel to switching transistors disposed in a frequency down conversion unit or a frequency up conversion unit, and local oscillator signals with predetermined phases and pulse widths are provided to the gates of the transistors such that a high frequency signal or an intermediate frequency signal is transferred to an output terminal at least two times during one cycle of a local oscillator signal.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a technology for up or down converting a frequency, and more particularly, to a frequency up and down converter which can up or down convert the frequency of an input signal using an oscillation signal with a frequency lower than an original frequency. 
         [0003]    2. Description of the Related Art 
         [0004]    In general, in a wireless communication system, in order to improve frequency selectivity characteristics for transmission and reception paths, frequency up and down converters for channels are needed for channel separation in an intermediate frequency (IF) analog frequency stage. 
         [0005]      FIG. 1  is a block diagram of a conventional frequency down converter. Referring to  FIG. 1 , a conventional frequency down converter includes a frequency down conversion unit  110 , a local oscillator signal generation unit  120 , and a transimpedance amplification unit  130 . 
         [0006]    The frequency down conversion unit  110  has a single balanced frequency down converting section and a double balanced frequency down converting section. The frequency down conversion unit  110  includes a first mixer  110 A and a second mixer  110 B. 
         [0007]    The first mixer  110 A is configured to control and convert high frequency signals RF_INP and RF_INN inputted thereto, into I channel intermediate frequency signals by using local oscillator signals LO A  and LO B . The second mixer  110 B is configured to control and convert the high frequency signals RF_INP and RF_INN into Q channel intermediate frequency signals IF_QP and IF_QN by using local oscillator signals LO C  and LO D . 
         [0008]    The transimpedance amplification unit  130  includes a transimpedance amplifier TIA, resistors R 1  and R 2  and capacitors C 1  and C 2 , and is configured to amplify the I channel intermediate frequency signals outputted from the first mixer  110 A using the component elements. Accordingly, amplified type I channel intermediate frequency signals IF_IP and IF_IN are outputted from the transimpedance amplifier TIA. 
         [0009]    The local oscillator signal generation unit  120  includes a plurality of local oscillator signal generators  121  to  124 . The waveforms of the local oscillator signals inputted to and outputted from the local oscillator signal generators  121  to  124  are shown in  FIG. 2 . 
         [0010]    Referring to  FIG. 2 , the local oscillator signal generators  121  to  124  receive pulse width modulated type local oscillator signals LO 0  and LO 270 , LO 180  and LO 90 , LO 0  and LO 90 , and LO 180  and LO 270  with different phases, and generate pulse width modulated type local oscillator signals LO A  and LO B , and LO C  and LO D  with a duty ratio equal to or less than 50% and a phase difference of 180° to be used in the first mixer  110 A and the second mixer  110 B. 
         [0011]      FIG. 3  is a block diagram of a conventional frequency up converter. Referring to  FIG. 3 , a conventional frequency up converter includes a frequency up conversion unit  310 , a local oscillator signal generation unit  320 , and a transimpedance amplifier  330 . 
         [0012]    The frequency up conversion unit  310  has a single balanced frequency up converting section and a double balanced frequency up converting section. The frequency up conversion unit  310  includes a first mixer  310 A and a second mixer  310 B. 
         [0013]    The first mixer  310 A is configured to control and convert I channel intermediate frequency signals IF_IP and IF_IN inputted thereto, into high frequency signals by using local oscillator signals LO A  and LO B . The second mixer  310 B is configured to control and convert Q channel intermediate frequency signals IF_QP and IF_QN inputted thereto, into high frequency signals by using local oscillator signals LO C  and LO D . 
         [0014]    The transimpedance amplifier  330  is configured to amplify the high frequency signals outputted from the common output terminals of the first mixer  310 A and the second mixer  310 B and output a positive polarity high frequency signal RF_OUTP and a negative polarity high frequency signal RF_OUTN. 
         [0015]    The local oscillator signal generation unit  320  includes a plurality of local oscillator signal generators  321  to  324 . The waveforms of the local oscillator signals inputted to and outputted from the local oscillator signal generators  321  to  324  are shown in  FIG. 2 . 
         [0016]    Referring to  FIG. 2 , the local oscillator signal generators  321  to  324  receive local oscillator signals LO 0  and LO 270 , LO 180  and LO 90 , LO 0  and LO 90 , and LO 180  and LO 270  with different phases, and generate local oscillator signals LO A  and LO B , and LO C  and LO D  with a duty ratio equal to or less than 50% and a phase difference of 180° to be used in the first mixer  310 A and the second mixer  310 B. 
         [0017]    In the conventional frequency down converter, when converting high frequency signals into intermediate frequency signals, local oscillator signals with a frequency corresponding to the frequency of the high frequency signals to be converted are used. In this regard, as a mobile communication system recently trends toward the use of a higher frequency signal, it is difficult to provide local oscillator signals with a correspondingly high frequency. 
         [0018]    Also, in the conventional frequency up converter, when converting intermediate frequency signals into high frequency signals, local oscillator signals with a high frequency corresponding to the frequency of the intermediate frequency signals are used. In this regard, as a mobile communication system recently trends toward the use of a higher frequency signal, it is difficult to provide local oscillator signals with a correspondingly high frequency. 
       SUMMARY OF THE INVENTION 
       [0019]    Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a frequency up and down converter, in which, when down converting a high frequency signal into an intermediate frequency signal or up converting an intermediate frequency signal into a high frequency signal by controlling switching elements using a local oscillator signal, a signal with a frequency to be converted is controlled a number of times during one cycle of the local oscillator signal, whereby the local oscillator signal with a frequency lower than an original frequency may be used. 
         [0020]    In order to achieve the above object, according to one aspect of the present invention, there is provided a frequency down converter for single-balanced down converting a frequency of a high frequency signal and transferring the high frequency signal to output terminals of an I channel positive polarity intermediate frequency signal, an I channel negative polarity intermediate frequency signal, a Q channel positive polarity intermediate frequency signal and a Q channel negative polarity intermediate frequency signal, the frequency down converter including: a first mixer including a plurality of MOS transistors which are connected in parallel to transfer the high frequency signal to the output terminal of the I channel positive polarity intermediate frequency signal a number of times with a predetermined phase difference, and a plurality of MOS transistors which are connected in parallel to transfer the high frequency signal to the output terminal of the I channel negative polarity intermediate frequency signal a number of times with a predetermined phase difference; a second mixer including a plurality of MOS transistors which are connected in parallel to transfer the high frequency signal to the output terminal of the Q channel positive polarity intermediate frequency signal a number of times with a predetermined phase difference, and a plurality of MOS transistors which are connected in parallel to transfer the high frequency signal to the output terminal of the Q channel negative polarity intermediate frequency signal a number of times with a predetermined phase difference; and a local oscillator signal generation unit configured to provide local oscillator signals with preselected phases and pulse widths to respective gates of the pluralities of MOS transistors connected in parallel to transfer the high frequency signal to the output terminals of the I channel positive polarity intermediate frequency signal, the I channel negative polarity intermediate frequency signal, the Q channel positive polarity intermediate frequency signal and the Q channel negative polarity intermediate frequency signal through the pluralities of MOS transistors the number of times during one cycle of a local oscillator signal. 
         [0021]    In order to achieve the above object, according to another aspect of the present invention, there is provided a frequency down converter for double-balanced down converting frequencies of a positive polarity high frequency signal and a negative polarity high frequency signal and transferring the high frequency signals to output terminals of an I channel positive polarity intermediate frequency signal, an I channel negative polarity intermediate frequency signal, a Q channel positive polarity intermediate frequency signal and a Q channel negative polarity intermediate frequency signal, the frequency down converter including: a first mixer including a plurality of MOS transistors which are connected in parallel to transfer the positive polarity high frequency signal to the output terminal of the I channel positive polarity intermediate frequency signal a number of times with a predetermined phase difference, a plurality of MOS transistors which are connected in parallel to transfer the positive polarity high frequency signal to the output terminal of the I channel negative polarity intermediate frequency signal a number of times with a predetermined phase difference; a plurality of MOS transistors which are connected in parallel to transfer the negative polarity high frequency signal to the output terminal of the I channel negative polarity intermediate frequency signal a number of times with a predetermined phase difference, and a plurality of MOS transistors which are connected in parallel to transfer the negative polarity high frequency signal to the output terminal of the I channel positive polarity intermediate frequency signal a number of times with a predetermined phase difference; a second mixer including a plurality of MOS transistors which are connected in parallel to transfer the positive polarity high frequency signal to the output terminal of the Q channel positive polarity intermediate frequency signal a number of times with a predetermined phase difference, a plurality of MOS transistors which are connected in parallel to transfer the positive polarity high frequency signal to the output terminal of the Q channel negative polarity intermediate frequency signal a number of times with a predetermined phase difference; a plurality of MOS transistors which are connected in parallel to transfer the negative polarity high frequency signal to the output terminal of the Q channel negative polarity intermediate frequency signal a number of times with a predetermined phase difference, and a plurality of MOS transistors which are connected in parallel to transfer the negative polarity high frequency signal to the output terminal of the Q channel positive polarity intermediate frequency signal a number of times with a predetermined phase difference; and a local oscillator signal generation unit configured to provide local oscillator signals with preselected phases and pulse widths to respective gates of the pluralities of MOS transistors connected in parallel to transfer the positive polarity high frequency signal and the negative polarity high frequency signal to the output terminals of the I channel positive polarity intermediate frequency signal, the I channel negative polarity intermediate frequency signal, the Q channel positive polarity intermediate frequency signal and the Q channel negative polarity intermediate frequency signal through the pluralities of MOS transistors the number of times during one cycle of a local oscillator signal. 
         [0022]    In order to achieve the above object, according to still another aspect of the present invention, there is provided a frequency up converter for single-balanced up converting frequencies of an I channel positive polarity intermediate frequency signal, an I channel negative polarity intermediate frequency signal, a Q channel positive polarity intermediate frequency signal and a Q channel negative polarity intermediate frequency signal and transferring the signals to an output terminal of a high frequency signal, the frequency up converter including: a first mixer including a plurality of MOS transistors which are connected in parallel to transfer the I channel positive polarity intermediate frequency signal to the output terminal of the high frequency signal a number of times with a predetermined phase difference, and a plurality of MOS transistors which are connected in parallel to transfer the I channel negative polarity intermediate frequency signal to the output terminal of the high frequency signal a number of times with a predetermined phase difference; a second mixer including a plurality of MOS transistors which are connected in parallel to transfer the Q channel positive polarity intermediate frequency signal to the output terminal of the high frequency signal a number of times with a predetermined phase difference, and a plurality of MOS transistors which are connected in parallel to transfer the Q channel negative polarity intermediate frequency signal to the output terminal of the high frequency signal a number of times with a predetermined phase difference; and a local oscillator signal generation unit configured to provide local oscillator signals with preselected phases and pulse widths to respective gates of the pluralities of MOS transistors connected in parallel to transfer the I channel positive polarity intermediate frequency signal, the I channel negative polarity intermediate frequency signal, the Q channel positive polarity intermediate frequency signal and the Q channel negative polarity intermediate frequency signal to the output terminal of high frequency signal through the pluralities of MOS transistors the number of times during one cycle of a local oscillator signal. 
         [0023]    In order to achieve the above object, according to yet still another aspect of the present invention, there is provided a frequency up converter for double-balanced up converting frequencies of an I channel positive polarity intermediate frequency signal, an I channel negative polarity intermediate frequency signal, a Q channel positive polarity intermediate frequency signal and a Q channel negative polarity intermediate frequency signal and transferring the signals to an output terminal of a positive polarity high frequency signal and an output terminal of a negative polarity high frequency signal, the frequency up converter including: a first mixer including a plurality of MOS transistors which are connected in parallel to transfer the I channel positive polarity intermediate frequency signal to the output terminal of the positive polarity high frequency signal a number of times with a predetermined phase difference, a plurality of MOS transistors which are connected in parallel to transfer the I channel positive polarity intermediate frequency signal to the output terminal of the negative polarity high frequency signal a number of times with a predetermined phase difference, a plurality of MOS transistors which are connected in parallel to transfer the I channel negative polarity intermediate frequency signal to the output terminal of the negative polarity high frequency signal a number of times with a predetermined phase difference, and a plurality of MOS transistors which are connected in parallel to transfer the I channel negative polarity intermediate frequency signal to the output terminal of the positive polarity high frequency signal a number of times with a predetermined phase difference; a second mixer including a plurality of MOS transistors which are connected in parallel to transfer the Q channel positive polarity intermediate frequency signal to the output terminal of the positive polarity high frequency signal a number of times with a predetermined phase difference, a plurality of MOS transistors which are connected in parallel to transfer the Q channel positive polarity intermediate frequency signal to the output terminal of the negative polarity high frequency signal a number of times with a predetermined phase difference, a plurality of MOS transistors which are connected in parallel to transfer the Q channel negative polarity intermediate frequency signal to the output terminal of the negative polarity high frequency signal a number of times with a predetermined phase difference, and a plurality of MOS transistors which are connected in parallel to transfer the Q channel negative polarity intermediate frequency signal to the output terminal of the positive polarity high frequency signal a number of times with a predetermined phase difference; and a local oscillator signal generation unit configured to provide local oscillator signals with preselected phases and pulse widths to respective gates of the pluralities of MOS transistors connected in parallel to transfer the I channel positive polarity intermediate frequency signal, the I channel negative polarity intermediate frequency signal, the Q channel positive polarity intermediate frequency signal and the Q channel negative polarity intermediate frequency signal to the output terminal of the positive polarity high frequency signal and the output terminal of the negative polarity high frequency signal through the pluralities of MOS transistors the number of times during one cycle of a local oscillator signal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description taken in conjunction with the drawings, in which: 
           [0025]      FIG. 1  is a block diagram of a conventional frequency down converter; 
           [0026]      FIG. 2  is a waveform diagram of local oscillator signals outputted from the local oscillator signal generation unit shown in  FIG. 1 ; 
           [0027]      FIG. 3  is a block diagram of a conventional frequency up converter; 
           [0028]      FIG. 4  is a block diagram of a single balanced frequency down converter in accordance with a first embodiment of the present invention; 
           [0029]      FIG. 5  is a block diagram of a double balanced frequency down converter in accordance with a second embodiment of the present invention; 
           [0030]      FIG. 6  is a block diagram of a single balanced frequency up converter in accordance with a third embodiment of the present invention; 
           [0031]      FIG. 7  is a block diagram of a double balanced frequency up converter in accordance with a fourth embodiment of the present invention; and 
           [0032]    In  FIG. 8 , (a) is a waveform diagram of frequency down conversion according to the conventional art, and (b) is a waveform diagram of frequency down conversion according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0033]    Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts. 
         [0034]      FIG. 4  is a block diagram of a single balanced frequency down converter in accordance with a first embodiment of the present invention. In  FIG. 4 , a single balanced frequency down converter includes a frequency down conversion unit  410  having a first mixer  410 A and a second mixer  410 B and a local oscillator signal generation unit  420  having a plurality of local oscillator signal generators  421  to  428 . 
         [0035]    Referring to  FIG. 4 , the first mixer  410 A includes a pair of first and second MOS transistors M 401  and M 402  which are sequentially switched and transfer a high frequency signal RF_IN to the output terminal of an I channel positive polarity intermediate frequency signal IF_IP, and a pair of third and fourth MOS transistors M 403  and M 404  which are sequentially switched and transfer the high frequency signal RF_IN to the output terminal of an I channel negative polarity intermediate frequency signal IF_IN. 
         [0036]    One terminals and the other terminals of the first MOS transistor M 401  and the second MOS transistor M 402  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the high frequency signal RF_IN and the other common connection terminal is connected to the output terminal of the I channel positive polarity intermediate frequency signal IF_IP. The gate of the first MOS transistor M 401  is connected to the terminal of a local oscillator signal LO A , and the gate of the second MOS transistor M 402  is connected to the terminal of a local oscillator signal LO B . 
         [0037]    One terminals and the other terminals of the third MOS transistor M 403  and the fourth MOS transistor M 404  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the high frequency signal RF_IN and the other common connection terminal is connected to the output terminal of the I channel negative polarity intermediate frequency signal IF_IN. The gate of the third MOS transistor M 403  is connected to the terminal of a local oscillator signal LO C , and the gate of the fourth MOS transistor M 404  is connected to the terminal of a local oscillator signal LO D . 
         [0038]    The second mixer  410 B includes a pair of fifth and sixth MOS transistors M 405  and M 406  which are sequentially switched and transfer the high frequency signal RF_IN to the output terminal of a Q channel positive polarity intermediate frequency signal IF_QP, and a pair of seventh and eighth MOS transistors M 407  and M 408  which are sequentially switched and transfer the high frequency signal RF_IN to the output terminal of a Q channel negative polarity intermediate frequency signal IF_QN. 
         [0039]    One terminals and the other terminals of the fifth MOS transistor M 405  and the sixth MOS transistor M 406  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the high frequency signal RF_IN and the other common connection terminal is connected to the output terminal of the Q channel positive polarity intermediate frequency signal IF_QP. The gate of the fifth MOS transistor M 405  is connected to the terminal of a local oscillator signal LO E , and the gate of the sixth MOS transistor M 406  is connected to the terminal of a local oscillator signal LO H . 
         [0040]    One terminals and the other terminals of the seventh MOS transistor M 407  and the eighth MOS transistor M 408  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the high frequency signal RF_IN and the other common connection terminal is connected to the output terminal of the Q channel negative polarity intermediate frequency signal IF_QN. The gate of the seventh MOS transistor M 407  is connected to the terminal of a local oscillator signal LO G , and the gate of the eighth MOS transistor M 408  is connected to the terminal of a local oscillator signal LO H . 
         [0041]    The first local oscillator signal generator  421  is configured to be inputted with a local oscillator signal LO 0  with the phase of 0° and a local oscillator signal LO 270  with the phase of 270° and generate the local oscillator signal LO A  with the phase of 0°. The second local oscillator signal generator  422  is configured to be inputted with a local oscillator signal LO 180  with the phase of 180° and a local oscillator signal LO 90  with the phase of 90° and generate the local oscillator signal LO B  with the phase of 180°. The third local oscillator signal generator  423  is configured to be inputted with the local oscillator signal LO 0  with the phase of 0° and the local oscillator signal LO 90  with the phase of 90° and generate the local oscillator signal LO C  with the phase of 90°. The fourth local oscillator signal generator  424  is configured to be inputted with the local oscillator signal LO 180  with the phase of 180° and the local oscillator signal LO 270  with the phase of 270° and generate the local oscillator signal LO D  with the phase of 270°. The fifth local oscillator signal generator  425  is configured to be inputted with a local oscillator signal LO 45  with the phase of 45° and a local oscillator signal LO 315  with the phase of 315° and generate the local oscillator signal LO E  with the phase of 45°. The sixth local oscillator signal generator  426  is configured to be inputted with a local oscillator signal LO 225  with the phase of 225° and a local oscillator signal LO 135  with the phase of 135° and generate the local oscillator signal LO F  with the phase of 225°. The seventh local oscillator signal generator  427  is configured to be inputted with the local oscillator signal LO 45  with the phase of 45° and the local oscillator signal LO 135  with the phase of 135° and generate the local oscillator signal LO G  with the phase of 135°. The eighth local oscillator signal generator  428  is configured to be inputted with the local oscillator signal LO 225  with the phase of 225° and the local oscillator signal LO 315  with the phase of 315° and generate the local oscillator signal LO H  with the phase of 315°. 
         [0042]    The local oscillator signal generation unit  420  generates the pulse width modulated type local oscillator signals as shown in  FIG. 2 . The four local oscillator signals LO 0 , LO 90 , LO 180  and LO 270  shown in  FIG. 2  have the phase difference of 90° and the duty ratio of 50%. However, since the local oscillator signal generation unit  420  uses the eight local oscillator signals LO 0 , LO 45 , LO 90 , LO 135 , LO 180 , LO 225 , LO 270  and LO 315 , these eight local oscillator signals have the phase difference of 45° and the duty ratio of 25%. 
         [0043]    Therefore, the first MOS transistor M 401  of the first mixer  410 A is turned on by the local oscillator signal LO A , and the high frequency signal RF_IN is transferred to the output terminal of the I channel positive polarity intermediate frequency signal IF_IP through the first MOS transistor M 401 . Thereafter, the second MOS transistor M 402  of the first mixer  410 A is turned on by the local oscillator signal LO B , and the high frequency signal RF_IN is transferred to the output terminal of the I channel positive polarity intermediate frequency signal IF_IP through the second MOS transistor M 402 . 
         [0044]    The third MOS transistor M 403  of the first mixer  410 A is turned on by the local oscillator signal LO C , and the high frequency signal RF_IN is transferred to the output terminal of the I channel negative polarity intermediate frequency signal IF_IN through the third MOS transistor M 403 . Thereafter, the fourth MOS transistor M 404  of the first mixer  410 A is turned on by the local oscillator signal LO D , and the high frequency signal RF_IN is transferred to the output terminal of the I channel negative polarity intermediate frequency signal IF_IN through the fourth MOS transistor M 404 . 
         [0045]    The fifth MOS transistor M 405  of the second mixer  410 B is turned on by the local oscillator signal LO B , and the high frequency signal RF_IN is transferred to the output terminal of the Q channel positive polarity intermediate frequency signal IF_QP through the fifth MOS transistor M 405 . Thereafter, the sixth MOS transistor M 406  of the second mixer  410 B is turned on by the local oscillator signal LO B , and the high frequency signal RF_IN is transferred to the output terminal of the Q channel positive polarity intermediate frequency signal IF_QP through the sixth MOS transistor M 406 . 
         [0046]    The seventh MOS transistor M 407  of the second mixer  410 B is turned on by the local oscillator signal LO G , and the high frequency signal RF_IN is transferred to the output terminal of the Q channel negative polarity intermediate frequency signal IF_QN through the seventh MOS transistor M 407 . Thereafter, the eighth MOS transistor M 408  of the second mixer  410 B is turned on by the local oscillator signal LO H , and the high frequency signal RF_IN is transferred to the output terminal of the Q channel negative polarity intermediate frequency signal IF_QN through the eighth MOS transistor M 408 . 
         [0047]    In this way, during one cycle of a local oscillator signal LO, the high frequency signal RF_IN is transferred two times to each of the output terminals of the intermediate frequency signals IF_IP, IF_IN, IF_QP and IF_QN through each pair of pairs of MOS transistors M 401  and M 402 , M 403  and M 404 , M 405  and M 406 , and M 407  and M 408  which perform switching operations. Accordingly, unlike the conventional single balanced frequency down conversion in which, during one cycle of the local oscillator signal LO, the high frequency signal RF_IN is transferred one time to each of the output terminals of the intermediate frequency signals IF_IP, IF_IN, IF_QP and IF_QN through a one corresponding MOS transistor, it is possible to perform single balanced frequency down conversion in the same way even by using a local oscillator signal with one half frequency. 
         [0048]    While it was described above that the respective pairs of MOS transistors M 401  and M 402 , M 403  and M 404 , M 405  and M 406 , and M 407  and M 408  are used in correspondence to the respective output terminals of the intermediate frequency signals IF_IP, IF_IN, IF_QP and IF_QN, it is to be noted that the present invention is not limited to such and an output signal with a higher frequency may be acquired using increased numbers of oscillators and switching MOS transistors by applying the same principle as described above. 
         [0049]      FIG. 5  is a block diagram of a double balanced frequency down converter in accordance with a second embodiment of the present invention. In  FIG. 5 , a double balanced frequency down converter includes a frequency down conversion unit  510  having a first mixer  510 A and a second mixer  510 B and a local oscillator signal generation unit  520  having a plurality of local oscillator signal generators  521  to  528 . 
         [0050]    Referring to  FIG. 5 , the first mixer  510 A includes a pair of first and second MOS transistors M 501  and M 502  which are sequentially switched and transfer a positive polarity high frequency signal RF_INP to the output terminal of an I channel positive polarity intermediate frequency signal IF_IP, a pair of third and fourth MOS transistors M 503  and M 504  which are sequentially switched and transfer the positive polarity high frequency signal RF_INP to the output terminal of an I channel negative polarity intermediate frequency signal IF_IN, a pair of fifth and sixth MOS transistors M 505  and M 506  which are sequentially switched and transfer a negative polarity high frequency signal RF_INN to the output terminal of the I channel negative polarity intermediate frequency signal IF_IN, and a pair of seventh and eighth MOS transistors M 507  and M 508  which are sequentially switched and transfer the negative polarity high frequency signal RF_INN to the output terminal of the I channel positive polarity intermediate frequency signal IF_IP. 
         [0051]    One terminals and the other terminals of the first MOS transistor M 501  and the second MOS transistor M 502  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the positive polarity high frequency signal RF_INP and the other common connection terminal is connected to the output terminal of the I channel positive polarity intermediate frequency signal IF_IP. The gate of the first MOS transistor M 501  is connected to the terminal of a local oscillator signal LO A , and the gate of the second MOS transistor M 502  is connected to the terminal of a local oscillator signal LO B . 
         [0052]    One terminals and the other terminals of the third MOS transistor M 503  and the fourth MOS transistor M 504  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the positive polarity high frequency signal RF_INP and the other common connection terminal is connected to the output terminal of the I channel negative polarity intermediate frequency signal IF_IN. The gate of the third MOS transistor M 503  is connected to the terminal of a local oscillator signal LO C , and the gate of the fourth MOS transistor M 504  is connected to the terminal of a local oscillator signal LO D . 
         [0053]    One terminals and the other terminals of the fifth MOS transistor M 505  and the sixth MOS transistor M 506  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the negative polarity high frequency signal RF_INN and the other common connection terminal is connected to the output terminal of the I channel negative polarity intermediate frequency signal IF_IN. The gate of the fifth MOS transistor M 505  is connected to the terminal of the local oscillator signal LO A , and the gate of the sixth MOS transistor M 506  is connected to the terminal of the local oscillator signal LO B . 
         [0054]    One terminals and the other terminals of the seventh MOS transistor M 507  and the eighth MOS transistor M 508  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the negative polarity high frequency signal RF_INN and the other common connection terminal is connected to the output terminal of the I channel positive polarity intermediate frequency signal IF_IP. The gate of the seventh MOS transistor M 507  is connected to the terminal of the local oscillator signal LO C , and the gate of the eighth MOS transistor M 508  is connected to the terminal of the local oscillator signal LO D . 
         [0055]    The second mixer  510 B includes a pair of ninth and tenth MOS transistors M 509  and M 510  which are sequentially switched and transfer the positive polarity high frequency signal RF_INP to the output terminal of a Q channel positive polarity intermediate frequency signal IF_QP, a pair of eleventh and twelfth MOS transistors M 511  and M 512  which are sequentially switched and transfer the positive polarity high frequency signal RF_INP to the output terminal of a Q channel negative polarity intermediate frequency signal IF_QN, a pair of thirteenth and fourteenth MOS transistors M 513  and M 514  which are sequentially switched and transfer the negative polarity high frequency signal RF_INN to the output terminal of the Q channel negative polarity intermediate frequency signal IF_QN, and a pair of fifteenth and sixteenth MOS transistors M 515  and M 516  which are sequentially switched and transfer the negative polarity high frequency signal RF_INN to the output terminal of the Q channel positive polarity intermediate frequency signal IF_QP. 
         [0056]    One terminals and the other terminals of the ninth MOS transistor M 509  and the tenth MOS transistor M 510  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the positive polarity high frequency signal RF_INP and the other common connection terminal is connected to the output terminal of the Q channel positive polarity intermediate frequency signal IF_QP. The gate of the ninth MOS transistor M 509  is connected to the terminal of a local oscillator signal LO E , and the gate of the tenth MOS transistor M 510  is connected to the terminal of a local oscillator signal LO F . 
         [0057]    One terminals and the other terminals of the eleventh MOS transistor M 511  and the twelfth MOS transistor M 512  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the positive polarity high frequency signal RF_INP and the other common connection terminal is connected to the output terminal of the Q channel negative polarity intermediate frequency signal IF_QN. The gate of the eleventh MOS transistor M 511  is connected to the terminal of a local oscillator signal LO G , and the gate of the twelfth MOS transistor M 512  is connected to the terminal of a local oscillator signal LO H . 
         [0058]    One terminals and the other terminals of the thirteenth MOS transistor M 513  and the fourteenth MOS transistor M 514  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the negative polarity high frequency signal RF_INN and the other common connection terminal is connected to the output terminal of the Q channel negative polarity intermediate frequency signal IF_QN. The gate of the thirteenth MOS transistor M 513  is connected to the terminal of the local oscillator signal LO E , and the gate of the fourteenth MOS transistor M 514  is connected to the terminal of a local oscillator signal LO F . 
         [0059]    One terminals and the other terminals of the fifteenth MOS transistor M 515  and the sixteenth MOS transistor M 516  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the negative polarity high frequency signal RF_INN and the other common connection terminal is connected to the output terminal of the Q channel positive polarity intermediate frequency signal IF_QP. The gate of the fifteenth MOS transistor M 515  is connected to the terminal of the local oscillator signal LO G , and the gate of the sixteenth MOS transistor M 516  is connected to the terminal of a local oscillator signal LO H . 
         [0060]    The local oscillator signal generation unit  520  generates the local oscillator signals LO A  to LO H  of the same patterns as those generated by the local oscillator signal generation unit  420  of  FIG. 4 . 
         [0061]    Therefore, the first MOS transistor M 501  and the fifth MOS transistor M 505  of the first mixer  510 A are simultaneously turned on by the local oscillator signal LO A . According to this fact, the positive polarity high frequency signal RF_INP is transferred to the output terminal of the I channel positive polarity intermediate frequency signal IF_IP through the first MOS transistor M 501 . At the same time, the negative polarity high frequency signal RF_INN is transferred to the output terminal of the I channel negative polarity intermediate frequency signal IF_IN through the fifth MOS transistor M 505 . 
         [0062]    Thereafter, the second MOS transistor M 502  and the sixth MOS transistor M 506  are simultaneously turned on by the local oscillator signal LO B . According to this fact, the positive polarity high frequency signal RF_INP is transferred to the output terminal of the I channel positive polarity intermediate frequency signal IF_IP through the second MOS transistor M 502 . At the same time, the negative polarity high frequency signal RF_INN is transferred to the output terminal of the I channel negative polarity intermediate frequency signal IF_IN through the sixth MOS transistor M 506 . 
         [0063]    Then, the third MOS transistor M 503  and the seventh MOS transistor M 507  are simultaneously turned on by the local oscillator signal LO C . According to this fact, the positive polarity high frequency signal RF_INP is transferred to the output terminal of the I channel negative polarity intermediate frequency signal IF_IN through the third MOS transistor M 503 . At the same time, the negative polarity high frequency signal RF_INN is transferred to the output terminal of the I channel positive polarity intermediate frequency signal IF_IP through the seventh MOS transistor M 507 . 
         [0064]    Next, the fourth MOS transistor M 504  and the eighth MOS transistor M 508  are simultaneously turned on by the local oscillator signal LO D . According to this fact, the positive polarity high frequency signal RF_INP is transferred to the output terminal of the I channel negative polarity intermediate frequency signal IF_IN through the fourth MOS transistor M 504 . At the same time, the negative polarity high frequency signal RF_INN is transferred to the output terminal of the I channel positive polarity intermediate frequency signal IF_IP through the eighth MOS transistor M 508 . 
         [0065]    The ninth MOS transistor M 509  and the thirteenth MOS transistor M 513  of the second mixer  510 B are simultaneously turned on by the local oscillator signal LO E . According to this fact, the positive polarity high frequency signal RF_INP is transferred to the output terminal of the Q channel positive polarity intermediate frequency signal IF_QP through the ninth MOS transistor M 509 . At the same time, the negative polarity high frequency signal RF_INN is transferred to the output terminal of the Q channel negative polarity intermediate frequency signal IF_QN through the thirteenth MOS transistor M 513 . 
         [0066]    Thereafter, the tenth MOS transistor M 510  and the fourteenth MOS transistor M 514  are simultaneously turned on by the local oscillator signal LO F . According to this fact, the positive polarity high frequency signal RF_INP is transferred to the output terminal of the Q channel positive polarity intermediate frequency signal IF_QP through the tenth MOS transistor M 510 . At the same time, the negative polarity high frequency signal RF_INN is transferred to the output terminal of the Q channel negative polarity intermediate frequency signal IF_QN through the fourteenth MOS transistor M 514 . 
         [0067]    Then, the eleventh MOS transistor M 511  and the fifteenth MOS transistor M 515  are simultaneously turned on by the local oscillator signal LO G . According to this fact, the positive polarity high frequency signal RF_INP is transferred to the output terminal of the Q channel negative polarity intermediate frequency signal IF_QN through the eleventh MOS transistor M 511 . At the same time, the negative polarity high frequency signal RF_INN is transferred to the output terminal of the Q channel positive polarity intermediate frequency signal IF_QP through the fifteenth MOS transistor M 515 . 
         [0068]    Next, the twelfth MOS transistor M 512  and the sixteenth MOS transistor M 516  are simultaneously turned on by the local oscillator signal LO H . According to this fact, the positive polarity high frequency signal RF_INP is transferred to the output terminal of the Q channel negative polarity intermediate frequency signal IF_QN through the twelfth MOS transistor M 512 . At the same time, the negative polarity high frequency signal RF_INN is transferred to the output terminal of the Q channel positive polarity intermediate frequency signal IF_QP through the sixteenth MOS transistor M 516 . 
         [0069]    In this way, during one cycle of a local oscillator signal LO, each of the positive polarity high frequency signal RF_INP and the negative polarity high frequency signal RF_INN is transferred two times to each of the output terminals of the I channel intermediate frequency signals IF_IP and IF_IN through each pair of four pairs of MOS transistors M 501  and M 502 , M 503  and M 504 , M 505  and M 506 , and M 507  and M 508 , and is transferred two times to each of the output terminals of the Q channel intermediate frequency signals IF_QP and IF_QN through each pair of the other four pairs of MOS transistors M 509  and M 510 , M 511  and M 512 , M 513  and M 514 , and M 515  and M 516 . 
         [0070]    Accordingly, unlike the conventional double balanced frequency down conversion in which, during one cycle of the local oscillator signal LO, each of the positive polarity high frequency signal RF_INP and the negative polarity high frequency signal RF_INN is transferred one time to each of the output terminals of the intermediate frequency signals IF_IP, IF_IN, IF_QP and IF_QN through a one corresponding MOS transistor, it is possible to perform double balanced frequency down conversion in the same way even by using a local oscillator signal with one half frequency. 
         [0071]    While it was described above that the respective pairs of MOS transistors M 501  and M 502 , M 503  and M 504 , M 505  and M 506 , M 507  and M 508 , M 509  and M 510 , M 511  and M 512 , M 513  and M 514 , and M 515  and M 516  are used in correspondence to the respective output terminals of the intermediate frequency signals IF_IP, IF_IN, IF_QP and IF_QN, it is to be noted that the present invention is not limited to such and an output signal with a higher frequency may be acquired using increased numbers of oscillators and switching MOS transistors by applying the same principle as described above. 
         [0072]      FIG. 6  is a block diagram of a single balanced frequency up converter in accordance with a third embodiment of the present invention. In  FIG. 6 , a single balanced frequency up converter includes a frequency up conversion unit  610  having a first mixer  610 A and a second mixer  610 B and a local oscillator signal generation unit  620  having a plurality of local oscillator signal generators  621  to  628 . 
         [0073]    Referring to  FIG. 6 , the first mixer  610 A includes a pair of first and second MOS transistors M 601  and M 602  which are sequentially switched and transfer an I channel positive polarity intermediate frequency signal IF_IP to the output terminal of a high frequency signal RF_OUT, and a pair of third and fourth MOS transistors M 603  and M 604  which are sequentially switched and transfer an I channel negative polarity intermediate frequency signal IF_IN to the output terminal of the high frequency signal RF_OUT. 
         [0074]    One terminals and the other terminals of the first MOS transistor M 601  and the second MOS transistor M 602  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the I channel positive polarity intermediate frequency signal IF_IP and the other common connection terminal is connected to the output terminal of the high frequency signal RF_OUT. The gate of the first MOS transistor M 601  is connected to the terminal of a local oscillator signal LO A , and the gate of the second MOS transistor M 602  is connected to the terminal of a local oscillator signal LO B . 
         [0075]    One terminals and the other terminals of the third MOS transistor M 603  and the fourth MOS transistor M 604  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the I channel negative polarity intermediate frequency signal IF_IN and the other common connection terminal is connected to the output terminal of the high frequency signal RF_OUT. The gate of the third MOS transistor M 603  is connected to the terminal of a local oscillator signal LO C , and the gate of the fourth MOS transistor M 604  is connected to the terminal of a local oscillator signal LO D . 
         [0076]    The second mixer  610 B includes a pair of fifth and sixth MOS transistors M 605  and M 606  which are sequentially switched and transfer a Q channel positive polarity intermediate frequency signal IF_QP to the output terminal of the high frequency signal RF_OUT, and a pair of seventh and eighth MOS transistors M 607  and M 608  which are sequentially switched and transfer a Q channel negative polarity intermediate frequency signal IF_QN to the output terminal of the high frequency signal RF_OUT. 
         [0077]    One terminals and the other terminals of the fifth MOS transistor M 605  and the sixth MOS transistor M 606  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the Q channel positive polarity intermediate frequency signal IF_QP and the other common connection terminal is connected to the output terminal of the high frequency signal RF_OUT. The gate of the fifth MOS transistor M 605  is connected to the terminal of a local oscillator signal LO E , and the gate of the sixth MOS transistor M 606  is connected to the terminal of a local oscillator signal LO F . 
         [0078]    One terminals and the other terminals of the seventh MOS transistor M 607  and the eighth MOS transistor M 608  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the Q channel negative polarity intermediate frequency signal IF_QN and the other common connection terminal is connected to the output terminal of the high frequency signal RF_OUT. The gate of the seventh MOS transistor M 607  is connected to the terminal of a local oscillator signal LO G , and the gate of the eighth MOS transistor M 608  is connected to the terminal of a local oscillator signal LO H . 
         [0079]    The local oscillator signal generation unit  620  generates the local oscillator signals LO A  to LO H  of the same patterns as those generated by the local oscillator signal generation unit  420  of  FIG. 4 . 
         [0080]    Therefore, the first MOS transistor M 601  of the first mixer  610 A is turned on by the local oscillator signal LO A , and the I channel positive polarity intermediate frequency signal IF_IP is transferred to the output terminal of the high frequency signal RF_OUT through the first MOS transistor M 601 . Thereafter, the second MOS transistor M 602  of the first mixer  610 A is turned on by the local oscillator signal LO B , and the I channel positive polarity intermediate frequency signal IF_IP is transferred to the output terminal of the high frequency signal RF_OUT through the second MOS transistor M 602 . 
         [0081]    The third MOS transistor M 603  of the first mixer  610 A is turned on by the local oscillator signal LO C , and the I channel negative polarity intermediate frequency signal IF_IN is transferred to the output terminal of the high frequency signal RF_OUT through the third MOS transistor M 603 . Thereafter, the fourth MOS transistor M 604  of the first mixer  610 A is turned on by the local oscillator signal LO D , and the I channel negative polarity intermediate frequency signal IF_IN is transferred to the output terminal of the high frequency signal RF_OUT through the fourth MOS transistor M 604 . 
         [0082]    The fifth MOS transistor M 605  of the second mixer  610 B is turned on by the local oscillator signal LO E , and the Q channel positive polarity intermediate frequency signal IF_QP is transferred to the output terminal of the high frequency signal RF_OUT through the fifth MOS transistor M 605 . Thereafter, the sixth MOS transistor M 606  of the second mixer  610 B is turned on by the local oscillator signal LO F , and the Q channel positive polarity intermediate frequency signal IF_QP is transferred to the output terminal of the high frequency signal RF_OUT through the sixth MOS transistor M 606 . 
         [0083]    The seventh MOS transistor M 607  of the second mixer  610 B is turned on by the local oscillator signal LO G , and the Q channel negative polarity intermediate frequency signal IF_QN is transferred to the output terminal of the high frequency signal RF_OUT through the seventh MOS transistor M 607 . Thereafter, the eighth MOS transistor M 608  of the second mixer  610 B is turned on by the local oscillator signal LO H , and the Q channel negative polarity intermediate frequency signal IF_QN is transferred to the output terminal of the high frequency signal RF_OUT through the eighth MOS transistor M 608 . 
         [0084]    In this way, during one cycle of a local oscillator signal LO, each of the intermediate frequency signals IF_IP, IF_IN, IF_QP and IF_QN is transferred two times to the output terminal of the high frequency signal RF_OUT through each pair of pairs of MOS transistors M 601  and M 602 , M 603  and M 604 , M 605  and M 606 , and M 607  and M 608  which perform switching operations. Accordingly, unlike the conventional single balanced frequency up conversion in which, during one cycle of the local oscillator signal LO, each of the intermediate frequency signals IF_IP, IF_IN, IF_QP and IF_QN is transferred one time to the output terminal of the high frequency signal RF_OUT through a one corresponding MOS transistor, it is possible to perform single balanced frequency up conversion in the same way even by using a local oscillator signal with one half frequency. 
         [0085]    While it was described above that the respective pairs of MOS transistors M 601  and M 602 , M 603  and M 604 , M 605  and M 606 , and M 607  and M 608  are used in correspondence to the respective terminals of the intermediate frequency signals IF_IP, IF_IN, IF_QP and IF_QN, it is to be noted that the present invention is not limited to such and an output signal with a higher frequency may be acquired using increased numbers of oscillators and switching MOS transistors by applying the same principle as described above. 
         [0086]      FIG. 7  is a block diagram of a double balanced frequency up converter in accordance with a fourth embodiment of the present invention. In  FIG. 7 , a double balanced frequency up converter includes a frequency up conversion unit  710  having a first mixer  710 A and a second mixer  710 B and a local oscillator signal generation unit  720  having a plurality of local oscillator signal generators  721  to  728 . 
         [0087]    Referring to  FIG. 7 , the first mixer  710 A includes a pair of first and second MOS transistors M 701  and M 702  which are sequentially switched and transfer an I channel positive polarity intermediate frequency signal IF_IP to the output terminal of a positive polarity high frequency signal RF_OUTP, a pair of third and fourth MOS transistors M 703  and M 704  which are sequentially switched and transfer the I channel positive polarity intermediate frequency signal IF_IP to the output terminal of a negative polarity high frequency signal RF_OUTN, a pair of fifth and sixth MOS transistors M 706  and M 707  which are sequentially switched and transfer an I channel negative polarity intermediate frequency signal IF_IN to the output terminal of the negative polarity high frequency signal RF_OUTN, and a pair of seventh and eighth MOS transistors M 707  and M 708  which are sequentially switched and transfer the I channel negative polarity intermediate frequency signal IF_IN to the output terminal of the positive polarity high frequency signal RF_OUTP. 
         [0088]    One terminals and the other terminals of the first MOS transistor M 701  and the second MOS transistor M 702  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the I channel positive polarity intermediate frequency signal IF_IP and the other common connection terminal is connected to the output terminal of the positive polarity high frequency signal RF_OUTP. The gate of the first MOS transistor M 701  is connected to the terminal of a local oscillator signal LO A , and the gate of the second MOS transistor M 702  is connected to the terminal of a local oscillator signal LO B . 
         [0089]    One terminals and the other terminals of the third MOS transistor M 703  and the fourth MOS transistor M 704  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the I channel positive polarity intermediate frequency signal IF_IP and the other common connection terminal is connected to the output terminal of the negative polarity high frequency signal RF_OUTN. The gate of the third MOS transistor M 703  is connected to the terminal of a local oscillator signal LO C , and the gate of the fourth MOS transistor M 704  is connected to the terminal of a local oscillator signal LO D . 
         [0090]    One terminals and the other terminals of the fifth MOS transistor M 705  and the sixth MOS transistor M 706  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the I channel negative polarity intermediate frequency signal IF_IN and the other common connection terminal is connected to the output terminal of the negative polarity high frequency signal RF_OUTN. The gate of the fifth MOS transistor M 705  is connected to the terminal of the local oscillator signal LO A , and the gate of the sixth MOS transistor M 706  is connected to the terminal of the local oscillator signal LO B . 
         [0091]    One terminals and the other terminals of the seventh MOS transistor M 707  and the eighth MOS transistor M 708  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the I channel negative polarity intermediate frequency signal IF_IN and the other common connection terminal is connected to the output terminal of the positive polarity high frequency signal RF_OUTP. The gate of the seventh MOS transistor M 707  is connected to the terminal of the local oscillator signal LO C , and the gate of the eighth MOS transistor M 708  is connected to the terminal of the local oscillator signal LO D . 
         [0092]    The second mixer  710 B includes a pair of ninth and tenth MOS transistors M 709  and M 710  which are sequentially switched and transfer a Q channel positive polarity intermediate frequency signal IF_QP to the output terminal of the positive polarity high frequency signal RF_OUTP, a pair of eleventh and twelfth MOS transistors M 711  and M 712  which are sequentially switched and transfer the Q channel positive polarity intermediate frequency signal IF_QP to the output terminal of the negative polarity high frequency signal RF_OUTN, a pair of thirteenth and fourteenth MOS transistors M 713  and M 714  which are sequentially switched and transfer a Q channel negative polarity intermediate frequency signal IF_QN to the output terminal of the negative polarity high frequency signal RF_OUTN, and a pair of fifteenth and sixteenth MOS transistors M 715  and M 716  which are sequentially switched and transfer the Q channel negative polarity intermediate frequency signal IF_QN to the output terminal of the positive polarity high frequency signal RF_OUTP. 
         [0093]    One terminals and the other terminals of the ninth MOS transistor M 709  and the tenth MOS transistor M 710  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the Q channel positive polarity intermediate frequency signal IF_QP and the other common connection terminal is connected to the output terminal of the positive polarity high frequency signal RF_OUTP. The gate of the ninth MOS transistor M 709  is connected to the terminal of a local oscillator signal LO E , and the gate of the tenth MOS transistor M 710  is connected to the terminal of a local oscillator signal LO F . 
         [0094]    One terminals and the other terminals of the eleventh MOS transistor M 711  and the twelfth MOS transistor M 712  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the Q channel positive polarity intermediate frequency signal IF_QP and the other common connection terminal is connected to the output terminal of the negative polarity high frequency signal RF_OUTN. The gate of the eleventh MOS transistor M 711  is connected to the terminal of a local oscillator signal LO G , and the gate of the twelfth MOS transistor M 712  is connected to the terminal of a local oscillator signal LO H . 
         [0095]    One terminals and the other terminals of the thirteenth MOS transistor M 713  and the fourteenth MOS transistor M 714  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the Q channel negative polarity intermediate frequency signal IF_QN and the other common connection terminal is connected to the output terminal of the negative polarity high frequency signal RF_OUTN. The gate of the thirteenth MOS transistor M 713  is connected to the terminal of the local oscillator signal LO E , and the gate of the fourteenth MOS transistor M 714  is connected to the terminal of a local oscillator signal LO F . 
         [0096]    One terminals and the other terminals of the fifteenth MOS transistor M 715  and the sixteenth MOS transistor M 716  are commonly connected with each other, and one common connection terminal is connected to the input terminal of the Q channel negative polarity intermediate frequency signal IF_QN and the other common connection terminal is connected to the output terminal of the positive polarity high frequency signal RF_OUTP. The gate of the fifteenth MOS transistor M 715  is connected to the terminal of the local oscillator signal LO G , and the gate of the sixteenth MOS transistor M 716  is connected to the terminal of a local oscillator signal LO H . 
         [0097]    The local oscillator signal generation unit  720  generates the local oscillator signals LO A  to LO H  of the same patterns as those generated by the local oscillator signal generation unit  420  of  FIG. 4 . 
         [0098]    Therefore, the first MOS transistor M 701  and the fifth MOS transistor M 705  of the first mixer  710 A are simultaneously turned on by the local oscillator signal LO A . According to this fact, the I channel positive polarity intermediate frequency signal IF_IP is transferred to the output terminal of the positive polarity high frequency signal RF_OUTP through the first MOS transistor M 701 . At the same time, the I channel negative polarity intermediate frequency signal IF_IN is transferred to the output terminal of the negative polarity high frequency signal RF_OUTN through the fifth MOS transistor M 705 . 
         [0099]    Thereafter, the second MOS transistor M 702  and the sixth MOS transistor M 706  are simultaneously turned on by the local oscillator signal LO B . According to this fact, the I channel positive polarity intermediate frequency signal IF_IP is transferred to the output terminal of the positive polarity high frequency signal RF_OUTP through the second MOS transistor M 702 . At the same time, the I channel negative polarity intermediate frequency signal IF_IN is transferred to the output terminal of the negative polarity high frequency signal RF_OUTN through the sixth MOS transistor M 706 . 
         [0100]    Then, the third MOS transistor M 703  and the seventh MOS transistor M 707  are simultaneously turned on by the local oscillator signal LO C . According to this fact, the I channel positive polarity intermediate frequency signal IF_IP is transferred to the output terminal of the negative polarity high frequency signal RF_OUTN through the third MOS transistor M 703 . At the same time, the I channel negative polarity intermediate frequency signal IF_IN is transferred to the output terminal of the positive polarity high frequency signal RF_OUTP through the seventh MOS transistor M 707 . 
         [0101]    Next, the fourth MOS transistor M 704  and the eighth MOS transistor M 708  are simultaneously turned on by the local oscillator signal LO D . According to this fact, the I channel positive polarity intermediate frequency signal IF_IP is transferred to the output terminal of the negative polarity high frequency signal RF_OUTN through the fourth MOS transistor M 704 . At the same time, the I channel negative polarity intermediate frequency signal IF_IN is transferred to the output terminal of the positive polarity high frequency signal RF_OUTP through the eighth MOS transistor M 708 . 
         [0102]    The ninth MOS transistor M 709  and the thirteenth MOS transistor M 713  of the second mixer  710 B are simultaneously turned on by the local oscillator signal LO D . According to this fact, the Q channel positive polarity intermediate frequency signal IF_QP is transferred to the output terminal of the positive polarity high frequency signal RF_OUTP through the ninth MOS transistor M 709 . At the same time, the Q channel negative polarity intermediate frequency signal IF_QN is transferred to the output terminal of the negative polarity high frequency signal RF_OUTN through the thirteenth MOS transistor M 713 . 
         [0103]    Thereafter, the tenth MOS transistor M 710  and the fourteenth MOS transistor M 714  are simultaneously turned on by the local oscillator signal LO F . According to this fact, the Q channel positive polarity intermediate frequency signal IF_QP is transferred to the output terminal of the positive polarity high frequency signal RF_OUTP through the tenth MOS transistor M 710 . At the same time, the Q channel negative polarity intermediate frequency signal IF_QN is transferred to the output terminal of the negative polarity high frequency signal RF_OUTN through the fourteenth MOS transistor M 714 . 
         [0104]    Then, the eleventh MOS transistor M 711  and the fifteenth MOS transistor M 715  are simultaneously turned on by the local oscillator signal LO G . According to this fact, the Q channel positive polarity intermediate frequency signal IF_QP is transferred to the output terminal of the negative polarity high frequency signal RF_OUTN through the eleventh MOS transistor M 711 . At the same time, the Q channel negative polarity intermediate frequency signal IF_QN is transferred to the output terminal of the positive polarity high frequency signal RF_OUTP through the fifteenth MOS transistor M 715 . 
         [0105]    Next, the twelfth MOS transistor M 712  and the sixteenth MOS transistor M 716  are simultaneously turned on by the local oscillator signal LO G . According to this fact, the Q channel positive polarity intermediate frequency signal IF_QP is transferred to the output terminal of the negative polarity high frequency signal RF_OUTN through the twelfth MOS transistor M 712 . At the same time, the Q channel negative polarity intermediate frequency signal IF_QN is transferred to the output terminal of the positive polarity high frequency signal RF_OUTP through the sixteenth MOS transistor M 716 . 
         [0106]    In this way, during one cycle of a local oscillator signal LO, each of the I channel intermediate frequency signals IF_IP and IF_IN is transferred two times to each of the output terminals of the high frequency signals RF_OUTP and RF_OUTN through each pair of four pairs of MOS transistors M 701  and M 702 , M 703  and M 704 , M 705  and M 706 , and M 707  and M 708 , and each of the Q channel intermediate frequency signals IF_QP and IF_QN is transferred two times to each of the output terminals of the high frequency signals RF_OUTP and RF_OUTN through each pair of the other four pairs of MOS transistors M 709  and M 710 , M 711  and M 712 , M 713  and M 714 , and M 715  and M 716 . 
         [0107]    Accordingly, unlike the conventional double balanced frequency up conversion in which, during one cycle of the local oscillator signal LO, each of the I channel intermediate frequency signals IF_IP and IF_IN and the Q channel intermediate frequency signals IF_QP and IF_QN is transferred one time to each of the output terminals of the high frequency signals RF_OUTP and RF_OUTN through a one corresponding MOS transistor, it is possible to perform double balanced frequency up conversion in the same way even by using a local oscillator signal with one half frequency. 
         [0108]    While it was described above that the respective pairs of MOS transistors M 701  and M 702 , M 703  and M 704 , M 705  and M 706 , M 707  and M 708 , M 709  and M 710 , M 711  and M 712 , M 713  and M 714 , and M 715  and M 716  are used in correspondence to the respective I channel intermediate frequency signals IF_IP and IF_IN and Q channel intermediate frequency signals IF_QP and IF_QN, it is to be noted that the present invention is not limited to such and an output signal with a higher frequency may be acquired using increased numbers of oscillators and switching MOS transistors by applying the same principle as described above. 
         [0109]    In other words, in the first to fourth embodiments of the present invention, by controlling the switching operations of the pairs of switching MOS transistors using the eight local oscillator signals LO A , LO B , LO G , LO D , LO E , LO F , LO G  and LO H  with the phase differences and duty ratios as described above, the frequency of the local oscillator signal LO to be down or up converted becomes one half of the frequency of the high frequency signal RF to be inputted or outputted. Through further decreasing the duty ratios (while increasing the number) of oscillator signals and correspondingly adding switching MOS transistors connected in parallel by using the same principle, the frequency of the local oscillator signal LO to be down or up converted may be decreased to one thirds, one fourths, etc. of the frequency of the high frequency signal RF to be inputted or outputted. 
         [0110]    In  FIG. 8 , (a) is a waveform diagram of frequency down conversion according to the conventional art, and (b) is a waveform diagram of frequency down conversion according to the present invention. Here, the frequency of a high frequency signal (RF) is 2.01 GHz, and the frequency of a local oscillator signal (LO) is 1 GHz. Accordingly, the frequency of an intermediate frequency signal (IF) is 10 MHz. In (a) and (b) of  FIG. 8 , waveforms  801  and  803  are differential waveforms of an I channel positive polarity node (IP) and an I channel negative polarity node (IN), and waveforms  802  and  804  are differential waveforms of a Q channel positive polarity node (QP) and a Q channel negative polarity node (QN). The two waveforms  801  and  803  and  802  and  804  have a phase difference of 90°, and this means that a signal is orthogonally down converted. As a result, in the present invention, it can be seen that a signal is precisely down converted even though a local oscillator signal (LO) with a low frequency is used. 
         [0111]    As is apparent from the above description, according to the embodiments of the present invention, when down converting a high frequency signal into an intermediate frequency signal or up converting an intermediate frequency signal into a high frequency signal by controlling switching elements using a local oscillator signal, a signal with a frequency to be converted is controlled a number of times during one cycle of the local oscillator signal, whereby the same frequency conversion performance may be achieved even by using the local oscillator signal with a lower frequency. 
         [0112]    Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and the spirit of the invention as disclosed in the accompanying claims.