中文说明：
matlab绘制不同概率各种占空比的矩形随机信号的功率谱密度，本人亲自编写，代码精简效率高，且结果准确（网上流传的各种绘制矩形随机信号功率谱密度的matlab代码能画对的极少见...）
English Description：
Matlab draws the power spectral density of rectangular random signals with different probabilities and various duty cycles. I wrote it myself. The code is concise, efficient and the results are accurate (it is very rare that various matlab codes circulating on the Internet can draw the power spectral density of rectangular random signals correctly...)