Nec Corporation

Fujio Nakagawa

Akira Kanemasa

An echo canceller includes a first transversal filter for generating a first echo canceling signal to be canceled from an output signal from a sampler, the first echo canceling signal corresponding to a first sampling value of an echo response waveform of an echo path by a sampling clock when no sampling clock jitter occurs, a second transversal filter for generating a second echo canceling signal corresponding to a difference between the first sampling value and a second sampling value when the sampling clock jitter occurs, two subtractors for canceling the first and second echo canceling signals from a digital reception signal output from the sampler, and a controller for detecting the sampling clock jitter and performing a control operation such that a tap coefficient value of the second filter is added to a tap coefficient value of the first filter to update the tap coefficient value of the first filter, and thereafter, the second echo canceling signal generating operation of the second filter is disabled.

Echo canceller

An echo canceller of this invention cancels an echo signal input to a sampler through an echo path upon 2-wire/4-wire conversion. The echo canceller includes a filter having a characteristic for reducing a tail of an echo response waveform and inserted between an output terminal of the sampler and a reception output terminal, a first transversal filter for generating a first canceling signal for canceling an echo signal sampled at equal sampling clock intervals after the echo signal passes through the filter, a second transversal filter for canceling a deviation of a sampling value obtained when sampling clock is jittered before the deviation passes through the filter, an enable/disable unit for enabling/disabling a tap output of the second transversal filter, and a controller for, from a moment at which the sampling clock is jittered, controlling the enable/disable unit to cancel a deviation in correspondence with a deviation value of an actual sampling value.

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Tokyo, Japan

Fujio Nakagawa