| 摘要 |
PURPOSE:To attain high speed convergence with high accuracy and a small circuit scale by using an IIR filter circuit whose stability is guaranteed, removing roughly waveform distortion and using an adaptive FIR filter so as to equalize the residual equalization with high accuracy. CONSTITUTION:A signal incoming from the subscriber line is inputted to an input terminal 1 and converted into a digital signal by an A/D conversion circuit 2. This signal selects the filtering coefficient of a coefficient control circuit 3 for the IIR filtering circuit in response to the level of the input signal to decide the equalizing characteristic of the IIR filter circuit 4. Then the inputted signal is subjected to rough equalization in the IIR filtering circuit 4. Then the signal is equalized with high accuracy by the FIR filtering circuit coefficient control circuit 5 and the adaptive FIR filtering circuit 6 to remove the attenuation distortion and phase distortion, and the result is outputted from an output terminal 7. Thus, the equalization is subjected to stable high speed conversion with high accuracy by a few number of times of operation processings.
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