对于线性系统，输入输出在某频率点为正弦，利用本程序可以得到改频率点的幅值比和相位差。data文件为两组数据，通过matlab读取xls文件，可以用来验证本程序。-For linear systems, input and output sine wave at a frequency point, the use of this program can change the frequency by the amplitude ratio and phase difference. data files for the two sets of data, read by matlab xls files, can be used to test the program.