Demodulators – Amplitude modulation demodulator – Having specific distortion – noise or other interference...
Patent
1985-07-05
1986-12-23
LaRoche, Eugene R.
Demodulators
Amplitude modulation demodulator
Having specific distortion, noise or other interference...
329131, 375 80, 375 98, H03D 300, H03D 324
Patent
active
046314890
ABSTRACT:
A sampled input signal is quantized to lie within a predetermined magnitude range. The quantized input signal is coupled to a bandpass filter which selects the digital signal to be processed. The bandlimited signal is then coupled to a feedback automatic gain control circuit which removes the slow variations in the envelope of the input signal. The output of the feedback AGC circuit is then coupled to a feedforward AGC circuit which removes the fast variations in the envelope of the input signal. The feedback AGC and the feed forward AGC circuits share a common envelope detector, that is composed of a squaring operation and low pass filter operation. The feedback AGC circuit also reduces the dynamic range of the input signal which is required of the feed forward AGC circuit. The processed signal is then demodulated with a quadrature FM detector. The output of the FM detector may be low pass filtered, and coupled to a D/A converter to produce an audio message signal.
REFERENCES:
patent: 4375618 (1983-03-01), Jett, Jr.
patent: 4506228 (1985-03-01), Kammeyer
"Communications Receivers of the Future", Frank P. Chiffy and Bjorn E. Bjerede, Signal, Nov./Dec. 1975, pp. 16-21.
IBM Technical Disclosure Bulletin, vol. 27, No. 10B, Mar. 1985, pp. 6334-6335, 375-398.
Laird Kevin M.
Rozanski Walt
Downey Joseph T.
LaRoche Eugene R.
Mis David
Motorola Inc.
Southard Donald B.
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