US 5,018,134 AGranted

Method for cancelling echo in a transmitter and an apparatus therefor

AssigneeHitachi, Ltd.

InventorsMasaru Kokubo, Tatsuko Shinotsuka, Tatsuya Kameyama, Motohiro Kokumai, Hirotaka Hara

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Abstract

A method for cancelling an echo in a network termination (NT) of a transmission system and an apparatus therefor are disclosed. The method comprises the steps of detecting an end of transmission of a specific data train in an up-going signal when the phase of the received clock is to be shifted for synchronization during the transmission of the up-going signal from the NT, shifting the phase of the receiving clock when the end of transmission is detected, sampling a residual echo signal of the echo of the specific data train not cancelled by the adaptive filter, determining a correction value for the output of the adaptive filter and storing the correction value and adding a sign corresponding to the direction of the phase shift to the correction value after the phase shift and adding the result to the output of the adaptive filter to cancel the echo of the specific data train.

Claims14

Dependent claims

A method for cancelling an echo in a transmitting apparatus comprising the steps of:

(a) detecting an incoming component which is derived from a transmitting signal transmitted from said transmitting apparatus and which enters into a receiving circuit of said transmitting apparatus via a transmitting medium;
(b) setting the output of an echo canceller in order to cancel said incoming component on the basis of the detected result of said incoming component;
(c) detecting a phase difference between an operational clock for transmitting a signal transmitted from another transmitting apparatus communicating with said transmitting apparatus and an operational clock of said transmitting apparatus for receiving said transmitted signal from said other transmitting apparatus;
(d) comparing said phase difference with a predetermined value;
(e) detecting the transmission of a particular, predetermined signal row from said transmitting apparatus;
(f) changing the phase of said operational clock of said transmitting apparatus after said detecting of said transmission of said particular signal row, when said phase difference becomes greater than said predetermined value;
and
(g) correcting said output of said echo controller when said operational clock phase of said transmitting apparatus is changed.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/444,851Filed 4 Dec 1989 · continuation
Priority: JP 62-28932018 Nov 1987
Granted: 21 May 1991
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

H04B 3/238
Using a replica of transmitted signal in the time domain, e.g. echo cancellers: using initial training sequence
H04B 3/232
Using a replica of transmitted signal in the time domain, e.g. echo cancellers: using phase shift, phase roll or frequency offset correction
H04B 3/231
Using a replica of transmitted signal in the time domain, e.g. echo cancellers: echo cancellers using readout of a memory to provide the echo replica
H04B
Transmission