Telephonic communications – Subscriber line or transmission line interface – Network interface device
Patent
1998-09-18
2000-04-11
Isen, Forester W.
Telephonic communications
Subscriber line or transmission line interface
Network interface device
379407, 381 92, 381 941, 367121, H04M 908, H03R 300
Patent
active
06049607&
ABSTRACT:
Interference canceling is provided for canceling, from a target signal generated from a target source, an interference signal generated by an interference source. The beam splitter beam-splits the target signal into a plurality of band-limited target signals band-limited frequency bands and beam-splits the interference signal into corresponding band-limited frequency bands. The adaptive filter adaptively filters each band-limited interference signal from each corresponding band-limited target signal. The inhibitor can permit the adaptive filter to adapt or change coefficients when a signal-to-noise ratio of the reference signal exceeds a predetermined threshold, to be determined periodically, over a signal-to-noise ratio of the main signal. The beam selector selects at least one of a plurality of beams for adaptive filtering by the adaptive filter representing a direction from which the main signal is received. The beam selector selects beams simultaneously to improve accuracy and, in particular, selects a beam having a fixed direction and a beam which rotates in direction. The noise gate gates the main signal adaptively filtered by the adaptive filter by opening the noise gate when a signal-to-noise ratio at the near end is above a predetermined threshold and closing the noise gate when the signal-to-noise ratio at the near end is below the predetermined threshold. When the target signal represents speech generated at a near end of a teleconference, the adaptive filter cancels an echo present in the reference signal broadcast to a far end of the teleconference.
REFERENCES:
patent: 4965834 (1990-10-01), Miller
patent: 5226016 (1993-07-01), Christman
patent: 5627799 (1997-05-01), Hoshuyama
patent: 5825898 (1998-10-01), Marash
Berdugo Baruch
Marash Joseph
Isen Forester W.
Kowalski Thomas J.
Lamar Signal Processing
Saint-Surin Jacques
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