Demodulators – Amplitude modulation demodulator – Having specific distortion – noise or other interference...
Patent
1987-05-22
1988-10-11
Grimm, Siegfried H.
Demodulators
Amplitude modulation demodulator
Having specific distortion, noise or other interference...
329122, 455207, 455208, 455209, 455263, 455266, H03D 300
Patent
active
047774495
ABSTRACT:
A carrier-tracking FM demodulator system for providing threshold extension relative to the demodulation of an FM signal, such as a television signal, is disclosed, wherein an effective system filtering response tracks the instantaneous carrier frequency of the FM signal, without frequency compression, utilizing filters of substantially fixed-tuned characteristics. The waveform fidelity of the demodulated output signal is substantially independent of the action of the carrier-tracking feedback control loop utilized in the demodulator system. In order to track the instantaneous carrier frequency, the invention employs a number of mixer means, in cascade, each of which is utilized in conjunction with a local-oscillator means or other local-carrier-frequency generator means. One or more bandwidth-window filter means is utilized in said cascade for controlling overall bandwidth and one or more product-selector filter means are employed in the cascade to exclude spurious products that may be generated in the mixing processes, which would otherwise be deleterious to FM threshold. A control loop is utilized to provide feedback between the output of a frequency detector means placed behind said cascade and one or more local-carrier-frequency inputs of one or more said local-carrier-frequency generator means. The arrangement of the elements is such that no net frequency shift is produced at said frequency detector, but a shift of overall filtering response is provided which tracks the FM signal with narrow bandwidth. The disclosed demodulator system is particularly suitable for FM signals comprising pulse modulation.
REFERENCES:
patent: 2279058 (1942-04-01), Reid
patent: 2510906 (1950-06-01), Reid
patent: 3544899 (1970-12-01), Gusyatinsky et al.
LandOfFree
Threshold-extension FM demodulator apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Threshold-extension FM demodulator apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Threshold-extension FM demodulator apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1960398