Multiplex communications – Wide area network – Packet switching
Patent
1985-08-09
1989-05-02
Ng, Jin F.
Multiplex communications
Wide area network
Packet switching
379410, H04B 323
Patent
active
048274720
ABSTRACT:
An echo canceller designed to cancel an echo signal [g(t)] generated in a send path (7) by a signal [f(t)] applied to a receive path (1) contains a subtractor (9) whose positive terminal receives a signal derived from the echo signal and whose negative terminal receives the output signal from a transversal filter (10) provided with means (12) for adjusting the filter coefficients in such a way that the component due to the echo signal is cancelled at the output of the subtractor (9).
This echo canceller comprises a delta encoder (14) for encoding at a sampling rate 1/T the signal f(t) entering the receive path (1) and for supplying at the input of the transversal filter (10) a delta-encoded signal (.DELTA.F.sub.n), a circuit (22) for forming at the sampling rate 1/T the difference signal (d.sub.n) between two consecutive samples of the signal entering the send path (7) and for applying this signal to the positive terminal of the subtractor (9), and finally an integrator (13) connected to the output of the subtractor (9) and supplying the output signal of the send path (7).
REFERENCES:
patent: 3975686 (1976-08-01), Appel
patent: 4024358 (1977-05-01), Virupaksha
patent: 4232400 (1980-11-01), Yamamoto et al.
patent: 4355214 (1982-10-01), Levy et al.
patent: 4386236 (1983-05-01), Ferrieu et al.
patent: 4386430 (1983-05-01), Treiber
patent: 4672665 (1987-06-01), Nagai et al.
S. Tanaka et al., "A Multichannel Echo Canceller System", NEC Research & Development, No. 49, Apr. 1978, pp. 58-64.
Barschall Anne E.
Briody Thomas A.
Haken Jack E.
Ng Jin F.
Telecommunications Radioelectriques et Telephoniques T.R.T.
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