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. 26, 1992
Filed:
Nov. 09, 1990
Donald L Chaffee, Park City, UT (US);
Mark P Mallory, Salt Lake City, UT (US);
Graham H Brand, El Cerrito, CA (US);
Intelligent Modem Corporation, Midvale, UT (US);
Abstract
A system and method for reducing echoes on a duplex communication channel having both transmitted and received signals carried thereon, particularly a telephone channel having digital data transmitted thereon by way of a modem. The transmitted signal is converted from a time domain signal to a frequency domain transmitted signal by a fast fourier transform process. The frequency domain transmitted signal is multiplied by a set of filter coefficients to generate estimated echo coefficients. The estimated echo coefficients are converted from the frequency domain to the time domain by an inverse fast fourier transform process and then subtracted from the received signal to generate a residual echo signal. The residual echo signal is converted to a frequency domain residual echo signal by a fast fourier transform process and then multiplied by the complex conjugate of the frequency domain transmitted signal to generate correlation frequency components. The correlation frequency components are then used to update the filter coefficients so as to minimize the residual echo and at least partially cancel the echo present on the communication channel.