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. 23, 1984
Filed:
Nov. 20, 1981
David D Falconer, Nepean, CA;
AT&T Bell Laboratories, Murray Hill, NJ (US);
Abstract
Asynchronous digital frequency shift keyed (FSK) signals are demodulated by using an autocorrelation type demodulator including digital integration. To this end, the autocorrelation function and digital integration are realized by generating integration increments, i.e., area increments, at the digital signal sampling points and accumulating them to obtain the integrated output. This is realized by turning to account a relationship between zero crossings of the received signal, zero crossings of a delayed version of the received signal and polarity of the product of the received signal and its delayed version relative to sampling points of the received digital signal. Specifically, the area increment in an n.sup.th sampling interval is determined by the time interval since the last zero crossing of the received signal before the n.sup.th sampling point, the time interval since the last zero crossing of the delayed signal before the n.sup.th sampling point and the polarity of the product signal at the n.sup.th sampling point.