MODULATING METHOD OF BASE CLOCK FOR DIGITAL CIRCUIT AND MODULATOR

PROBLEM TO BE SOLVED: To output a clock modulated equally with a base clock on the average by calculating the position of a switching edge following a prescribed switching edge by a specified expression for calculation. SOLUTION: The position of a switching edge following the prescribed switching edge is calculated by the expression ai+2=(ai+p-((N-1)/2-Zi+1)) mod p. In this case, (p) is the number of portions at equal intervals per 1/2 cycle, N is an odd number of possible switching edges and Z is a random number. Thus, frequencies modulated by a corresponding number of random numbers can be provided, individual frequencies are time-averaged to correspond to a basic frequency and an exact time base to the clock can be used. Especially, when the random, number is inverted after (n) cycles and the inverted random number is used for deriving the switching edge, the random number can be selected. Thus, even when the selection of the random number to be used is unsuitable, the frequency modulated on the average corresponds to the basic frequency.