| 摘要 |
PURPOSE:To obtain a demodulation circuit which performs the demodulation suited to the corresponding frequency by detecting the carrier wave frequency of a frequency modulated wave in case a signal to be demodulated undergoes the modulation of frequency with either one of plural carrier wave frequencies. CONSTITUTION:A demodulating circuit main body including a signal extracting means that is switched to extract only a desired demodulation signal is provided together with a synchronizing separating circuit which separates a synchronizing signal from the output of the demodulating circuit main body, a frequency discriminating circuit which discriminates the carrier frequencies equal to the frequency modulating waves of the demodulation signals within a period corresponding to the synchronizing signal obtained by said synchronizing separating circuit, and a means which switches the signal extracting means for demodulating circuit main body by the output of the frequency discriminating circuit and activating said signal extracting means. Then the demodulation is made possible in response to the corresponding carrier wave frequency even in case plural carrier wave frequencies exist for the frequency modulated wave of the demodulation signal. Thus it is possible to obtain a satisfactory demodulation signal. |
