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:
Feb. 13, 2001
Filed:
Apr. 29, 1998
Edgar Velez, Kanata, CA;
Ian Dublin, Ottawa, CA;
Richard Buz, Rohnert Park, CA (US);
Sisay Yirga, Nepean, CA;
Nortel Networks Limited, Quebec, CA;
Abstract
A blind convergence process for an adaptive decision feedback equalizer having an quadrature amplitude modulation (QAM) slicer, a forward filter defined by a plurality of forward tap coefficients and a feedback filter defined by a plurality of feedback tap coefficients. The blind convergence process includes the step of initializing the forward tap coefficients of the forward filter and the feedback tap coefficients of the feedback filters with predetermined values. The QAM slicer operates in two modes: a clustering mode and a decision directed mode. The clustering mode includes the step of updating only the forward tap coefficients of the forward filter for a prescribed start-up QAM index (such a 4 QAM). The decision directed mode is predefined for set of QAM indexes having values n,, n,, . . . n,, and includes: updating the forward tap coefficients of the forward filter for a QAM index n,selected from the predefined set of QAM indexes, and updating the feedback tap coefficients of the feedback filter for the QAM index n,selected from the predefined set of QAM indexes. The decision directed processing steps are repeating the next QAM index n,of the predefined set of QAM indexes until the equalizer has converged to its highest available QAM index or until the equalizer has converged to the highest operable QAM index (constellation). The QAM index set can be {4,16,64,256}.