Taking account of the transmission characteristics of the diaphragm and the saturation of the gain in the process of light amplifying,the evolution of the beam inside the Cassegrain multi-pass amplifier is numerically simulated by using the ray-tracing and split-step fast Fourier-Bessel transform(SSFFT) methods,the annular beam is coming from Q-switched Nd∶glass laser with ring cavity.

If the frequencies between bus bar and transmission line are much different,the sampling with the same time interval will bring about errors in the Fourier algorithm.

Currently, a number of methods proposed for calculating the phasors of harmonic components of signals using the Fourier algorithm seem to make electrical engineers puzzled as to which to choose from.

After introducing the correlative theory of phaselet algorithm and analyzing Fourier algorithm and improved Fourier algorithm,the ability of eliminating harmonic current and decaying direct current component of these algorithms are analyzed and compared,and conclusions are given.

Influence on some main-apparatus protection performance by adopting DFT-based digital relays;