DIGITAL FILTER ARITHMETIC DEVICE

PURPOSE:To improve the ripple eliminating effect over an optional frequency region, by setting the number of output signals of a shift mean value calculating device at such a value with which the sum total of phase intervals of the time series data on the number of said output signals is approximate to an integer- fold value of the cycle of the time series data. CONSTITUTION:When the input frequency varies from fO by DELTAf, the basic frequency is equal to 2fA for the ripple component of the output PF1 of a shift mean value calculating device 4. The phase interval of the data is prescribed by 2pi(2fA)/fs. Therefore the shift means value of the time series data is obtained by a device 4A. The number of data is defined as NA to be used to the calculation of the shift mean value so as to delete completely the ripple component for fA= fAO (fAO: frequency of signal PF1 having its ripple component is eliminated by the device 4A). In such a case, it is satisfactory to set the sum total of phase intervals of NA units of data equal to an integer-fold value of the cycle of the time series data with a specific equation. In this case, fAO is equal to kA.fs/ 2.NA (kA: a positive integer and fs: sample frequency). The deviation DELTAfA is minimized to fO by selecting kA and NA respectively.