Frequency analysis method and apparatus, and spectrum spreading demodulation method and apparatus

摘要

A method for performing frequency analysis by executing discrete Fourier transform with a smaller capacity of a memory than in usual FFT processing, without reducing the frequency resolution. A-power-of-two N_A=2^a (where "a" is an integer) memories for discrete Fourier transform are prepared. A former-stage calculation step of taking out frequency components of an input signal having a-power-of-two N_B=2^b (where "b" is an integer and b>a) data items, in a comb manner and of calculating N_A intermediate data items and a latter-stage calculation step of applying fast Fourier transform to the intermediate data items obtained in the former-stage calculation step, by using the N_A memories for discrete Fourier transform are executed 2^b-a times with the frequency components taken out in the comb manner being changed, to execute discrete Fourier transform through 2^b-a operations.