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 f