IMPROVEMENT OF FFT SPECTRA BY SYNCHRONIZATION OF INPUT SIGNAL AT FIRST AND LAST ZERO-CROSSING POINTS

Abstract A new procedure called "zero-cross synchronization method" is proposed to improve the frequency spectrum obtained by fast Fourier transformation (FFT). Out of digitally sampled data only those between the first and the last zero-crossing points with the slopes of the same sign are selected and used in FIT analysis. Then the discontinuity which appears at the boundary when a periodic function is constructed is removed automatically. As no window function is necessary, the original wave remains free from distortion. The frequency spectra obtained by this method are shown to be much improved compared with those by the conventional one.