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:
Sep. 07, 1999
Filed:
Jan. 30, 1997
Timothy G Laud, Libertyville, IL (US);
Dennis M Mutzabaugh, Mount Prospect, IL (US);
Zenith Electronics Corporation, Glenview, IL (US);
Abstract
A symbol sync acquisition circuit for a digital VSB signal finds sync pattern correlations in the incoming signal. Initially both positive and negative sync pattern correlations are accorded equal weight, with non sync pattern correlations being accorded a negative weight. Values are accumulated in a segment integrator and stored in a FIFO having a location for each symbol position in a segment. A comparator initially produces an output when sync pattern correlations are found that add to a given value. After a relatively small number of correlations, as tabulated in a confidence counter, a VCO is enabled to change its frequency under control of error pulses based upon the symbol sync. After a greater number of sync pattern correlations, the symbol position in the segment is fixed, sliding to a new symbol location in the FIFO is precluded, the signal polarity is determined and changed, if necessary, and a higher threshold is established for the comparator. The confidence counter continues to build after lock is attained. Should confidence be lost, the system resets and acquisition is started from the beginning.