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:
Jun. 21, 1994
Filed:
Oct. 25, 1993
Sangil Park, Austin, TX (US);
Garth D Hillman, Austin, TX (US);
Motorola Inc., Schaumburg, IL (US);
Abstract
A direct-path echo cancellation circuit includes a loudspeaker (12), first and second microphones (14, 16), and an in-phase signal cancellation circuit (21, 43). The first and second microphones (14, 16) are positioned adjacent the loudspeaker (12) in order to receive in-phase direct-path echo components (31, 32) of an output signal from the loudspeaker (12). The in-phase signal cancellation circuit (21 or 43) combines the in-phase direct-path echo components of the output signal in order to cancel the direct-path echo components. Direct-path echo cancellation helps to reduce howling and/or oscillation in a full-duplex speakerphone system. Also, direct-path echo cancellation provides more dynamic range to an input signal which is provided to a speakerphone signal processing system (26).