| 摘要 |
PURPOSE:To reduce the redundancy of a circuit and to attain the stable AM demodulation by actuating a phase synchronizing circuit constituting an FM demodulator as an oscillator having the same frequency as the input signal of the phase synchronizing circuit in an AM demodulation mode, and applying an input to a multiplier to constitute an AM demodulator. CONSTITUTION:The satellite broadcast signal is supplied to an input terminal (a), than applied to a phase synchronizing circuit 7 via an input filter part 11, high frequency amplifier 1 and a high frequency signal switch circuit 6. The oscillation frequency of a voltage control oscillator 72 is switched in steps for coincidence with the reception desired signal frequency. Then the FM modulation is carried out. The ground broadcast signal is supplied to an input terminal (b), then supplied to phase locking circuit 7 via the part 11, high frequency amplifier 2, frequency mixer 4 and the part via the circuit 6. Thus the oscillator 72 has oscillations with an oscillation frequency which is coincident with the supplied signal frequency. Then, the oscillation output emerges at an output terminal (j). The coincidence of phase is obtained by a phase shifter 5 between the oscillation signal and the output signal of the mixer 4. Then the oscillation signal is supplied to a multiplier 8 for acquisition of a product. Thus, an AM demodulator is obtained to acquire the demodulation signal from the multiplier 8.
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