METHOD AND APPARATUS FOR DETECTING CYCLE AND PHASE OF SINE WAVE BY DISCRETE FOURIER TRANSFORM

摘要

PURPOSE:To accurately calculate the cycle and phase of a sine wave by detecting the max. spectrum of the spectra obtained by applying discrete Fourier transform and the peripheral spectrum thereof. CONSTITUTION:The output from the memory circuit 3 of the sample data of a sine wave signal A is subjected to discrete Fourier transform by a Fourier transform circuit 4 and the real component Fr(k) and imaginary component Fi(k) of the Fourier transform vector F(k) thereof are stored in a memory circuit 5. An operation circuit 6 calculates the height S(k)=[Fr(k)<2>+Fi(k)<2>]<1/2> of a spectrum from both components and the max. spectrum position k=n0 thereof is calculated by a max. value detection circuit 7. An operation circuit 8 calculates the deviation up to the actual max. spectrum position from the max. spectrum position k=n0. An operation circuit 9 calculates the cycle P and phase phi of the sine wave A from the fraction DELTA and the real component Fr(k) and imaginary component Fi(k) of the vector F(k) to output the same.