Full duplex speakerphone

Details Full duplex speakerphone Full duplex speakerphone

1995-03-10

1997-08-12

Matar, Ahmad F.

Telephonic communications

Substation or terminal circuitry

For loudspeaking terminal

379390, 379411, H04M 908

Patent

active

056573847

ABSTRACT:
A full duplex speakerphone for connection to a telephone system employs adaptive FIR filters for acoustic and electrical echo cancellation in a novel combination with analog gain controls responsive to incoming signal levels and a transmit level control responsive to the receive signal power level. The particular combination minimizes the amount of digital signal processing required to maintain full duplex operation by holding the signal dynamic range within predetermined limits.

REFERENCES:
patent: 4922530 (1990-05-01), Kenney et al.
patent: 5313498 (1994-05-01), Sano
patent: 5351291 (1994-09-01), Menez et al.
DSP Microcomputer, Analog Devices, Inc., ADSP-2101 (Data Sheet, Rev. A, Undated).
Cascadable Adaptive Finite Impulse Response Digital Filter (CAFIR); Motorola, Inc. DSP56200 (Technical Summary BR283, 1986).
Digital Signal Processing Laboratory Using the ADSP-21-01 Microcomputer, Chapter 10, pp. 287-291, Vinay K. Ingle and John G. Proakis, Prentice Hall; Copyright 1991, Analog Devices, Inc.
Full Duplex Speakerphone with Acoustic and Electric Echo-Canceller Utilizing the DSP56200 Cascadable Adaptive FIR Filter Chip, Sangil Park, Proceedings of Midcon/90 Technical Conference on Electronic and Electrical Technology, Dallas, Texas, Sep. 11-13, 1990.
Digital Voice Echo Canceller with TMS32020, David Messerschmitt, David Hedberg, Christopher Cole, Amine Haoui and Peter Winship; Digital Signal Processing Applications with the TMS320 Family, vol. 1, Chapter 15, pp. 417-436, Texas Instruments, 1986 (Reprinted 1989).
The TMS320 Family of Digital Signal Processors, Kun-Shan Lin, Gene A. Frantz, and Ray Simar, Jr., Proceedings of the IEEE, vol. 75, No. 9, pp. 1143-1159, Sep. 1987; Reprinted 1989, pp. 26-28.

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