FM Receiver

Details FM Receiver FM Receiver

1980-06-23

1982-10-26

Olms, Douglas W.

179 1GE, H04H 500

Patent

active

043563503

ABSTRACT:
Stereo composite signals and 38 KHz sub-carrier switching signal are fed to a stereo demodulator. The 38 KHz sub-carrier switching signal is generated from the phase-lock loop circuit and is transmitted to the stereo demodulator circuit via a gain-controlled circuit.
The output of an FM detector is applied to a high-pass filter which works to take out undesirable high-frequency components that are contained in the FM detection outputs. The level of the high-frequency components is detected by a detector.
The output signal of the detector is applied to the gain-controlled circuit to control the gain of the gain-controlled circuit. When the level of undesirable high-frequency components obtained by the high-pass filter increases, the gain of the gain-controlled circuit is decreased, whereby the amplitude level of 38 KHz sub-carrier switching signal transmitted to the stereo demodulator is lowered.
Thus, it is possible to suppress the development of beat signals of audible frequencies, due to the interference between undesirable high-frequency components contained in the outputs of the FM detector and harmonic components in the 38 KHz sub-carrier signals.

REFERENCES:
patent: 3634626 (1972-01-01), Staley
patent: 3673342 (1972-06-01), Muller
patent: 3823268 (1974-07-01), Modafferi
patent: 4032717 (1977-06-01), Mallon
patent: 4037057 (1977-07-01), Ogita et al.
"Theorie und Anwendungen des Phase-Locked Loops", von Roland Best, Elektroniker, 11/1976, pp. 18-25.
"Service an Stereo-Decodern", U. Prestin, Funk-Technik, 1964, pp. 660-661.
"Integrierte Schaltungen fur Stereo-Decoder", R. Jagberger, Funk-Technik, 1971, Nr. 15, pp. 549-553.

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