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:
Apr. 30, 2002
Filed:
Mar. 31, 1999
John Eugene Lane, Austin, TX (US);
Patrick K. Kelly, Toney, AL (US);
Robert V. Holland, Madison, AL (US);
Garth D. Hillman, Austin, TX (US);
Motorola, Inc., Schaumburg, IL (US);
Abstract
A speakerphone system ( ) implements automatic gain control (AGC) when it is in a talk mode. While in the talk mode, the speakerphone system ( ) applies a gain factor determined by conventional AGC techniques. The inverse of this gain factor is applied to the received signal to avoid the need to adapt the coefficients of an echo canceller, such as an acoustic echo canceller (AEC) ( ), as the volume level changes. The speakerphone system ( ) determines whether it is in the talk, double-talk, or listen mode by adaptively changing energy thresholds which define these modes, in dependence on the distribution of ratios of the transmitted energy to received energy. The speakerphone system ( ) also varies a loop gain in dependence on the separation between the distribution of energy ratios in the talk mode and in the receive mode. This automatic loop gain adjustment ensures loop stability.