FM noise threshold extension demodulator apparatus

Details FM noise threshold extension demodulator apparatus FM noise threshold extension demodulator apparatus

1976-03-31

1977-07-12

Safourek, Benedict V.

Demodulators

Amplitude modulation demodulator

Having specific distortion, noise or other interference...

325473, 325347, 325377, 329134, H03D 300

Patent

active

040357309

ABSTRACT:
Apparatus for lowering the noise threshold at which FM and other angle modulated signals may be demodulated is described wherein an oscillating limiter provided by an amplitude limiter having a bandpass filter in regenerative feedback relationship therewith is connected ahead of the demodulator. The bandpass filter is made tunable in response to a steering signal developed by processing the frequency proportional signal at the output of the demodulator to attenuate high frequency components thereof which are outside the baseband of the signals and adjusting the amplitude of the signal so that the center frequency of the bandpass filter is caused to substantially match the frequency of the frequency modulated signal. The steering signal circuit has electrical inertia, thus during click events the oscillating limiter will oscillate at a frequency which matches the best available estimate of the instantaneous frequency of the modulated signal, thereby minimizing both impulse noise (clicks) and discontinuities in the output, frequency demodulated (base band) signal during a click event.

REFERENCES:
patent: 3092780 (1963-06-01), Fisher
patent: 3195059 (1965-07-01), Adams
patent: 3243604 (1966-03-01), Johnson
patent: 3281698 (1966-10-01), Rose, Jr. et al.
patent: 3611169 (1971-10-01), Hess

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