| 摘要 |
PURPOSE: To prevent the inversion phenomenon of an FM signal by digital processing with simple circuitry by inputting the reproduced FM signal to a BPF and adding the output signal thereof to an original digital signal through a nonlinear circuit. CONSTITUTION: The BPF allows passage of only the prescribed band component (9.5MHz±300kBz) of the reproduced FM signal subjected to digitalization processing and outputs the signal having zero-crossing waveforms even in a period of a lowered decreased signal amplitude when the FM signal is inputted to the BPF as the signal having the waveforms possessing the non-zero crossing distortions to be the cause for an inversion phenomenon. The FM signal is suppressed in its amplitude by the nonlinear circuit 2 and is made to have the waveforms in which the parts of the large amplitude are drastically suppressed. The signal is mixed with the original signal by an adder 3 and is intensified in the high-frequency range with respect to the original signal. The signal is outputted as the signal of the zero-crossing waveforms to an FM demodulation circuit.
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