JPS5560327A - Filter unit - Google Patents

Abstract

PURPOSE:To obtain both amplitude information and phase information by making a comparison between a higher harmonic component, obtained by analyzing a distortion waveform in terms of a higher harmonic, and that included in this distortion waveform and then by carrying on arithmetic unit a difference between the both becomes zero. CONSTITUTION:Distortion waveform f(t) is inputted from point (X) and in the beginning of arithmetic, outputs ancos nomega0t and bnisn nomega0t are not appearing. As the arithmetic advances, a frequency component of nomega0 in f(t) appears at point (Y) and a difference from a frequency component of nomega0 included in f(t) is successively inputted and summed up by sample holding circuit 5', thereby continuing the arithmetic. When a value at point (Y) agrees completely with frequency component n0 of f(t), an input at point (X), frequency component nomega0 of an arithemetic input at point (Z) is zero. Since the sample holding circuit has an integral adding function, point (Y) shows values equal in amplitude and phase to nomega0 in f(t) at this point in time even if no input arrives. Namely, BPF extracting only nomega0 can be obtained between points (X) and (Y).