Telephonic communications – Substation or terminal circuitry – For loudspeaking terminal
Patent
1993-10-25
1994-06-21
Dwyer, James L.
Telephonic communications
Substation or terminal circuitry
For loudspeaking terminal
379389, 379391, 379410, 379409, 379388, H04M 900
Patent
active
053234588
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).
REFERENCES:
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patent: 4636586 (1987-01-01), Schiff
patent: 4956838 (1990-09-01), Gilloire et al.
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patent: 5027393 (1991-06-01), Yamamura et al.
patent: 5062102 (1991-10-01), Taguchi
patent: 5121426 (1992-06-01), Baumhauer, Jr. et al.
patent: 5187741 (1993-02-01), Erving et al.
Hillman Garth D.
Park Sang-il
Dwyer James L.
Hill Daniel D.
Motorola Inc.
Saint-Surin Jacques M.
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