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:
Mar. 31, 2015
Filed:
Mar. 19, 2010
Akio Yamaguchi, Tokyo, JP;
Akio Yamaguchi, Tokyo, JP;
Yugengaisya Cepstrum, Tokyo, JP;
Abstract
A howling canceller which suppresses occurrence of howling even when an open loop gain exceeds '1' in the whole reproduction band. In the howling canceller, an adaptive filter () operates a digital received voice signal with a tap coefficient to generate a pseudo echo; a subtractor () subtracts the pseudo echo from a digital transmitted voice signal to generate a residual signal; and an amplitude limiting circuit () limits the absolute value of the amplitude of the digital received voice signal to be equal to or smaller than a predetermined threshold which ensures that all of a D/A converter (), a power amplifier (), a speaker (), a microphone (), a microphone amplifier (), and an A/D converter () operate in a linear operation area, and outputs the amplitude-limited digital received voice signal to the D/A converter () and the adaptive filter ().