Patent ID: 6693863
Filing Date: 2004-02-17
Classification: G11B,H03M

Abstract:
An asymmetry correcting circuit for correcting a vertically asymmetric distortion of an input signal waveform in an analog-to-digital converter which quantizes the input signal waveform in accordance with a quantization reference voltage and converts the quantized waveform into a digital signal of predetermined bits, said asymmetry correcting circuit comprising:a first envelope detection circuit for detecting the envelope of a positive peak of the input signal waveform; a second envelope detection circuit for detecting the envelope of a negative peak of the input signal waveform; an adding circuit for outputting a sum voltage of the positive peak voltage obtained from said first envelope detection circuit and the negative peak voltage obtained from said second envelope detection circuit; a multiplying circuit for multiplying the sum voltage, which is outputted from said adding circuit, by a predetermined offset adjustment coefficient; and a quantization reference voltage control circuit for shifting, in response to the output signal of said multiplying circuit, the median of the quantization reference voltage of said analog-to-digital converter DC-wise in conformity with the offset derived from the asymmetry of the input signal, and controlling the upper limit and the lower limit of the quantization reference voltage to the values that correspond to the offset quantity.