说明：  第一个程序为模拟产生一个正态随机序列X(n)，画出产生的随机序列波形、相关函数（与理论曲线对比） 和功率谱密度。第二个程序为产生一个信号X(n)，绘出信号及其幅度频谱曲线，当中心频率向左搬移f0＝200Hz时，求出其低通等效信号，并绘出其幅度频谱、信号的同相、正交分量及包络。当中心频率向左搬移f0＝100Hz时，求出其低通等效信号，并绘出其幅度频谱、信号的同相、正交分量及包络。
(The first program to simulate the amount of generating a normal random sequence X (n), a random sequence of waveforms generated by the correlation function draw (with comparative theoretical curve) And power spectral density. The second program to generate a signal X (n), and draw the signal amplitude spectrum curve, move to the left when the center frequency f0 = 200Hz, obtaining low-pass equivalent signal, and draw its amplitude spectrum signal with phase and quadrature components of the envelope. When the center frequency shift f0 = 100Hz left when obtaining low-pass equivalent signal, and draw its magnitude spectrum, the in-phase signal and quadrature component envelope.)