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:
May. 28, 2002
Filed:
Apr. 17, 1998
Ernest T. Stroud, Greensboro, NC (US);
Other;
Abstract
A &pgr;/4 DQPSK modulator includes a rotated and offset &pgr;/4 encoder that provides encoded I, Q constellation indices values using positive integers. The positive integer I and Q values are input to a digital filter that provides filtered I, Q constellation indices values. These filtered values are then rotated and offset back to conventional &pgr;/4 DQPSK constellation values, modulated and transmitted. Since the rotated and offset &pgr;/4 encoder provides I, Q constellation indices as positive integers, the filters are implemented as multiplierless digital filters which significantly reduces the complexity of the filters. Specifically, the multiplierless digital filters can be implemented using shift registers and summers. In a preferred embodiment the filters are programmable. In addition, using positive integers to represent the rotated and offset &pgr;/4 signalling constellation indices allows the indices to be represented as a binary value with less bits in contrast to prior art systems. Significantly, representing the indices with less bits further reduces the complexity of the digital filters.