Detector for AM-FM signals

Details Detector for AM-FM signals Detector for AM-FM signals

1975-04-07

1976-12-21

Grimm, Siegfried H.

Demodulators

Amplitude modulation demodulator

Having specific distortion, noise or other interference...

307233R, 307235R, 325317, 329101, 329103, 329138, 329142, 329147, 330 30D, H03D 322, H03D 500

Patent

active

039991385

ABSTRACT:
A detector for AM or FM signals is described. The detector employs a differentially connected emitter follower pair to which an in-phase and a phase-shifted signal are respectively applied. The emitter follower pair produces an output waveform with controllably spaced zero crossings which is the "greater of" the applied waveforms. For FM operation, the phase shift is made linearly frequency dependent, being in quadrature at resonance. In FM operation, the zero crossings are sensed to produce a succession of variable width unidirectional pulses whose widths are proportional to the frequency deviation. Amplitude variations in the variable width pulses may then be removed and integration in a filter with an audio frequency time constant recovers the FM modulation information. For AM operation, a phase shift of 180.degree. is used, producing full wave rectification. The AM information is then recovered from the rectified signal using the same integrating filter used for FM. The invention has preferred application to integrated circuit fabrication.

REFERENCES:
patent: 3022461 (1962-02-01), Wilcox, Jr.
patent: 3519944 (1970-07-01), Avins

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