It is possible to easily design an FIR filter having an arbitrary frequency characteristic only by inputting a waveform of a desired frequency characteristic as an image without having any special knowledge, i.e., by inputting a waveform of a desired frequency characteristic as a numerical value series and performing reverse FFT of this to obtain a filter coefficient group. Moreover, by performing a special rounding calculation to the numerical value series obtained by the reverse FFT, it is possible to simplify the filter coefficient value without lowering the filter characteristic accuracy and significantly reduce the number of times a multiplier as a filter constituting element is used. Furthermore, by performing window multiplication to the result of the reverse FFT, it is possible to increase the length of the numerical value series input firstly so as to minimize the frequency error and minimize the number of filter coefficients, thereby simplifying the configuration of the digital filter to be designed.
展开▼
