PURPOSE: To clearly display the generation of moire interference after frequency conversion predicted in advance, coefficient arrangement in accordance with frequency characteristic, and coefficient supply sequence, etc., in equations by specifying a coefficient multiplied by a signal relating to each tap of a filter.

CONSTITUTION: A signal of frequency m*fc (fc: the number of unit clock frequencies) using an arithmetic circuit in which the signal relating to each tape of a FIR type digital filter consisting of N taps is multiplied by an arbitrary coefficient is converted to a signal of sampling frequency n*fc. When (n) and N show odd numbers, the coefficient multiplied by the signal relating to each tap is set as a value shown in equation I, and also, the signal in equation II is nullified assuming the impulse response of a low-pass filter of clock frequency m*n*fc and taps n*N as s0-s(m*N-1), a coefficient string formed in a group by jumping (n) impulse responses as G[k]=[sk...sk+n*(N-1)], coset dividing an integer (i) by (j) as iJj, and the number of clocks of m*fc from a reference timing as (l).