说明：  由已知表达式画出原始波形和它的功率谱，并编制一个互相关函数程序，要求提取特定频率的成分，画出变换过程中的波形和功率谱。
(Drawn from the known expression of the original waveform and its power spectrum, and the preparation of a cross-correlation function procedure that requires the extraction of specific frequency components, draw in the process of transformation and power spectrum waveforms.)