| 摘要 |
Echo cancellers provide echo return loss enhancement by subtracting a replica of the echo signal from the echo returned via the two-wire to four-wire transition. The echo replica is derived from the signal incoming from the far end by signal processing which consists of a convolution and adaptive modeling that is used to model echo paths caused by the imperfections of the two-wire to four-wire transition. An improved echo return loss enhancement (ERLE) is obtained by dynamic range compression of the incoming signal prior to processing and dynamic range extension following processing. The range extension is slaved to a control signal from the ranged compressor, providing proper compensation for the compressed signal, but insuring that processing noise and other extraneous signals have been adversely treated.
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