FM Noise suppressor

Claim 1

In an FM stereo demodulation system having detection means which receives a detected stereo composite signal and which detects a noise pulse in said detected stereo composite signal; gate means which receives said detected stereo composite signal at a first terminal thereof and a control terminal thereof being controlled by a control signal obtained from said detection means so as to derive a noise-suppressed signal from a second terminal thereof; reproduction means which receives said detected stereo composite signal without intervention of said gate means and which reproduces a subcarrier signal for stereo signal demodulation in synchronism with a pilot signal in said detected stereo composite signal; and an FM stereo demodulation means which receives said noise-suppressed signal and said subcarrier signal so as to derive a left signal and a right signal; the improvement wherein said reproduction means comprises a phase locked loop circuit which includes a phase comparator circuit having a first input coupled to receive said pilot signal and a second input; a low-pass filter circuit coupled to the output of said phase comparator circuit, a voltage controlled oscillator circuit coupled to the output of said low-pass filter circuit, and a frequency divider circuit coupled to the output of said voltage controlled oscillator circuit, the output of said frequency divider circuit providing a 19 KHz signal that is coupled to the second input of said phase comparator circuit.