The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 11, 1988
Filed:
May. 22, 1987
Edward O'Connor, Cleveland, OH (US);
Other;
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.