HIGH-SENSITIVITY FM SIGNAL DEMODULATION SYSTEM

摘要

PCT No. PCT/JP81/00206 Sec. 371 Date Feb. 18, 1983 Sec. 102(e) Date Feb. 18, 1983 PCT Filed Aug. 31, 1981 PCT Pub. No. WO83/00973 PCT Pub. Date Mar. 17, 1983.The present invention relates to the improved demodulation system which improves the noise characteristics for the demodulation of a wideband television FM signal. A variable bandpass filter (8), the center frequency and the bandwidth of which are controllable, for improving C/N, is inserted at the output of a reference bandpass filter (7) in an FM signal path. The bandwidth of the variable bandpass filter (8) is controlled so that said bandwidth is wide when the input carrier level is high, and said bandwidth is narrow when the input carrier level is low. The center frequency of the variable bandwidth filter (8) is controlled so that said center frequency follows to the instantaneous frequency of the color sub-carrier component (3.58 MHz). Said color sub-carrier component is derived by a narrow-band bandpass filter (10) coupled with the output of said discriminator (9) for controlling the center frequency of the variable bandpass filter (8).