| 摘要 |
PROBLEM TO BE SOLVED: To simplify circuit configuration, and to reduce cost and power consumption. SOLUTION: The transmitter has an orthogonal modulation circuit 2 generating an orthogonal modulation signal SVE by modulating a differential common- mode signal SSI and a differential orthogonal signal SSQ, a power amplifier 4 amplifying the orthogonal modulation signal SVE and outputting a transmission signal STR, a variable attenuator 6 attenuating a part of the transmission signal STR in proper quantity an orthogonal demodulation circuit 7 demodulating a signal SFE for a feedback input through the variable attenuator 6 to a common-mode demodulation signal SUI and an orthogonal demodulation signal SUQ, and a subtractor 8 generating the differential common-mode signal SSI by subtracting the common-mode demodulation signal SUI from a common- mode input signal SII and generating the differential orthogonal signal SSQ by subtracting the orthogonal demodulation signal SUQ from an orthogonal input signal SIQ. Further, the transmitter has a gain variable amplifier 3 amplifying the orthogonal modulation signal SVE at a fixed gain and outputting the signal SVE, and a gain control section 11 controlling the gain of the gain variable amplifier 3 in response to the voltage of the signal SFE for the feedback.
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