| 摘要 |
PROBLEM TO BE SOLVED: To improve the precision of demodulation by using not a sharp low pass filter for shaping the waveform of an FM signal demodulation circuit but a simple one. SOLUTION: When an FM video input signal S1 obtained by FM-modulating a carrier with a video signal is inputted to a video amplifier 1, a plus FM output signal S2 a and a minus FM output signal S22 b whose phase is deviated from the plus FM output signal S2 a by 180 degrees are outputted to differentiation circuits 2a and 2b. When pulse signals differentiated in the differentiation circuits 2a and 2b and obtained are added, a pulse output signal S3 having the frequency twice as much as the FM video input signal S1 is obtained. In the pulse output signal S3 , an apparent frequency difference between the carrier and a video signal is enlarged, and a low pass filter 3 which waveform-shapes the pulse output signal S3 can precisely demodulate the signal where the frequency difference between the carrier and the video signal is small. |
