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. 13, 1988
Filed:
Aug. 04, 1987
Randy D Nash, Dacula, GA (US);
Hayes Microcomputer Products, Inc., Norcross, GA (US);
Abstract
A fast phase reference recovery apparatus for use in a data communication system employing a signal constellation which is variant for certain rotations which will produce local minima in the phase error signal output of a phase lock loop. The incoming signal is rotated by one or more phase shifting networks, the outputs of which are provided to constellation decision circuits for the constellation in use. One of the constellation decision circuits will be locked on to the correct local minimum and thus on to the proper phase constellation, and the others will be locked onto incorrect rotations of the constellation. The magnitudes of the errors produced by the constellation decision circuits are compared and selection of the data signals from the proper circuit is made based on the relative magnitudes of these error signals. In preferred forms, the comparison of the magnitudes of the error signals is averaged over a predetermined number of baud times to improve reliability. The apparatus is self-locking on to the proper phase reference without the use of training or synchronization sequences.