Quasi-synchronous sampling algorithm and its applications II High accurate spectrum analysis of periodic signal

For Pt. I, see ibid., pp. 88-93 (1993). As one of the applications of the quasi-synchronous algorithm, a method to improve the spectrum analysis of periodic signals is described. Consisting of a quasi-synchronous window whose DTFT (discrete-time Fourier transform) has as small side-lobes as desired to reduce long-range leakage, and a compensation algorithm to reduce short-range leakage after the normal fast Fourier transform, this method will give much more accurate results of the amplitudes as well as the phases than the conventional method, especially for higher frequency components, when there exists an undesirable asynchronous deviation. This technique is also suited to analyzing multiple frequency signals and signals containing interharmonics. The only constraint is that the minimum frequency interval between two adjacent components of the signal should be wider than the window´s resolution