公开(公告)号：JPS62140518A

公开(公告)日：1987-06-24

申请号：JP28065285

申请日：1985-12-13

Applicant: ADVANTEST CORP

Inventor： YAMAGUCHI TAKAHIRO ,  ARAKAWA NORIO ,  OGAMI TAKAYUKI ,  OZAWA HIROMI

IPC: H03M1/04 ,  H03M1/00 ,  H03M1/20

Abstract: PURPOSE:To suppress the increase of noise power, also to reduce modulation noise, and also to reduce each instantaneous quantizing error, by containing an offset voltage generating means for generating an offset voltage which is varied by an integer multiple or a non-integer multiple of a quantizing step of an A/D converter. CONSTITUTION:An offset voltage -O outputted from an offset voltage generating means 6 is added to a random noise N. The offset voltage -O is varied by + or -nq (n is an integer or a non-integer), in case when a quantizing step is denoted as (q). For instance, (n) is varied as +4, 0, -4, 0, +4..., and a period T0 of the variation is selected to a period of (m) times of a sampling period Ts in an A/D converter 1. A signal which has been A/D-converted by the A/D converter 1 is supplied to, for instance, a high speed Fourier transformation device 9, and in the high speed Fourier transformation device 9, a signal of a time area is converted to a signal of a frequency area, the signal of the frequency area is added and averaged in accordance with a time series in an average means 11, and a quantizing error is averaged.