| 摘要 |
PURPOSE:To suppress a residual echo attended with sudden change in the phase by converting a sample of an echo replica obtained from the transmission data stored in an echo canceller when the phase is changed suddenly attended with the frequency control in a digital PLL and outputting the sample value obtained through the conversion at the timing phase after the phase change. CONSTITUTION:The sample value of the echo replica is outputted one after another according to the storage content of a memory storing the transmission data signal and incorporated in the echo canceller. Since the data signal stored in the echo canceller is sent already to a tranmission line when the phase is changed momentarily, the sample valueof the echo replica generated from it is converted and a value at the phase after the phase change of the echo replica erasing the echo correctly and formed from the sample value at the substantial phase is formed as a new sample value. That is, the sample value and its interpolated waveform shown in broken lines are formed from the sample and its interpolated waveform shown in full lines. Further, the converter of the sample value is realized by a transversal filter as the principle.
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