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:
Nov. 08, 1977
Filed:
Aug. 09, 1976
Richard Dennis Gitlin, Monmouth Beach, NJ (US);
John Stewart Thompson, Tinton Falls, NJ (US);
Bell Telephone Laboratories, Incorporated, Murray Hill, NJ (US);
Abstract
The circuit complexity of a closed-loop echo cancellation system for use in a two-way communication circuit is reduced by employing a second adjustable signal processing network of the transversal type positioned in the control loop to emulate the characteristic of a recursive adjustable signal processing network. The two signal processing networks in the control loop are adjusted simultaneously to effect echo cancellation. The second signal processing network compensates for the effect of transmission poles in the echo return path and reduces the duration of the impulse response of the echo return path significantly so that the first signal processing network in the control loop is greatly simplified. A third signal processing network of the recursive type is adjusted in accordance with the internal settings of the second network to perform signal processing inverse to that of the second network. The recursive network is utilized to provide a clear signal path through the echo cancellation system which is essentially free of echo.