JPS6454909A - Fm demodulation circuit - Google Patents

Abstract

PURPOSE:To eliminate the deterioration of picture quality due to moire and set the FM carrier frequency lower by providing a moire component generating circuit comprising a BPF, a multiplier circuit and a multiplier or the like. CONSTITUTION:An FM signal (a) from a terminal 1 is demodulated by a demodulator 2 and a demodulation signal (b) is fed to a generating circuit 5. A 2fC component is filtered by a BPF 6 in the generating circuit 5 and the result is fed to a multiplier 9. Moreover, the fC component is filtered by a BPF 7 from the signal (b), doubled by a doubler circuit 8 and a 2fS component and a signal (c) are fed to the multiplier 9. A 2fC+ or -2fS component being a signal (d) is generated from the multiplier 9. The signal (d) is fed to a subtractor 4 via a phase adjusting circuit 10 and an amplitude adjusting circuit 11. The subtractor 4 subtracts an output circuit 11 being an output of the generating circuit 5 from a demodulation signal b' via a delay circuit 3 to obtain a signal (e), which is outputted to an output terminal 12.