本程序是功率谱密度的仿真比较,关于三个信号源的具体情况参见《现代数字信号处理导论》上册，P202，习题5。

实验方法：周期图法、自相关法和协方差法。

-this procedure is the power spectral density of the simulation, 3 signal source on the specific circumstances, see the "modern digital signal processing" Introduction to the first volume, P202, Exercise 5. Experimental Methods : Chart cycle, since the correlation and covariance method.