FM Demodulator with variable bandpass filter

Details FM Demodulator with variable bandpass filter FM Demodulator with variable bandpass filter

1982-04-22

1986-01-07

LaRoche, Eugene R.

Demodulators

Amplitude modulation demodulator

Having specific distortion, noise or other interference...

329136, 329139, 455266, H03D 300

Patent

active

045636516

ABSTRACT:
The threshold level for demodulating an FM signal, for instance a television picture signal, has been improved or lowered by adaptively restricting the bandwidth of the signal using an adaptive bandpass filter, and therefore, the picture quality and/or S/N ratio of the demodulated television signal has been improved. The adaptive bandpass filter has enough bandwidth when the signal level is sufficiently higher than the threshold level, but is narrow when the signal level is close to or lower than the threshold level. The bandwidth of the adaptive bandpass filter is adjusted according to the total power of the input FM signal and C/N (the carrier signal to noise) ratio. The improvement of the threshold level is almost 2 dB.

REFERENCES:
patent: 4326297 (1982-04-01), Sato et al.
patent: 4339828 (1982-07-01), Chasek
patent: 4342000 (1982-07-01), Ogita
patent: 4356568 (1982-10-01), Ogita et al.
Van Dasler, G. et al., "A Threshold Extension Demodulator", Phillips Telecommunication Review, vol. 31, No. 3, pp. 131-147 (Oct. 1973).

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