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:
Jun. 02, 1987
Filed:
Aug. 05, 1985
Dale A Heatherington, Alpharetta, GA (US);
Hayes Microcomputer Products, Inc., Norcross, GA (US);
Abstract
An improved quadrature differential phase shift keyed signal demodulator for use in a modem is shown. A delay circuit (12) delays an input signal for a portion of a baud time. Synchronous detectors (21, 23) mix the original and delayed input signals with coherent reference signals to obtain detected outputs which are alternately provided to a processor (60) by a multiplexer (25). The processor (60) determines the phase shift and provides the demodulated data. An offset baud clock phase locked loop (40) provides a baud clock which is offset by a ninety degree phase lag. The offset baud clock caused the multiplexer (25) to provide detected outputs to the processor (60) for the center one-half of each baud. The result is a demodulator with fewer components and an improved data error rate.