| 摘要 |
PROBLEM TO BE SOLVED: To reduce the circuit scale by providing a local oscillation circuit and using a changeover circuit, two mixer circuits and aπ/2 phase shift circuit in common for an FM demodulation circuit and an orthogonal demodulation circuit. SOLUTION: An output of an intermediate frequency amplifier circuit 4 is outputted in the case of demodulating an FM signal and an output of a local oscillation circuit 6 is outputted in the case of demodulating a quadrature modulation signal through a switch 7 throwing its position by a switching control signal S101. In the case of demodulating the FM signal, a 1st frequency mixer circuit 51 mixes frequencies of an intermediate frequency signal and the intermediate frequency signal via the switch 7 and a 2nd frequency mixer circuit 52 mixes frequencies of the intermediate frequency signal and the intermediate frequency signal whose phase is shifted byπ/2, then the circuit 52 provides an output of the frequency- demodulated signal. On the other hand, in the case of demodulating a quadrature modulation signal, the 1st frequency mixer circuit 51 mixes frequencies of the intermediate frequency signal and a local oscillation frequency signal and the 2nd frequency mixer circuit 52 mixes frequencies of the intermediate frequency signal and the local oscillation frequency signal whose phase is shifted byπ/2, then the circuit 51 provides an output of an in-phase demodulation signal (I signal) and the circuit 52 provides an output of an inverted phase demodulation signal (Q signal).
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