| 摘要 |
PURPOSE: To reduce the sum total of noise in a signal band by shaping the quantization noise to superpose it on a high frequency area. CONSTITUTION: The difference between an output signal Y and an input signal X of a ternary quantizer 160 is inputted to an integrator 120 and is integrated. The difference between the output signal of the integrator 120 and the signal obtained by amplifying the output Y of the quantizer 160 twice in an amplifier 171 is inputted to an integrator 140 in the second stage and is integrated, and the output is inputted to a quantizer 160. The quantizer 160 receives the output of the integrator 140 and outputs three values 0 and±1 with±0.5 as thresholds. Consequently, the output spectrum of a noise shaper 100 has the spectrum where the signal obtained by subjecting most of the quantization noise to differentiation of second order is superposed on the input of the noise shaper 100. Thus, the noise sum total in the signal band is reduced without damaging the conventional S/N characteristic. When one-sample delay data of the quantizer 160 is 0, the product between stored data for delay and a positive coefficient smaller than one is supplied to the integrator 120.
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