说明：  说明三个分段相连的信号的傅里叶变换和时频分析,注,在该程序中，用到了子子程序tfstft.m, 还要用到显示程序 tfrqview及其他程序，
(Description of the three segment connected to the signal' s Fourier transform and frequency analysis, Note, used sub subroutine tfstft.m is in the program, also used to display the program tfrqview and other programs.)