说明：  一组取值为+/-1的随机序列，每两个数据之间插入3个0，然后将序列通过一个设计好的根升余弦滤波器，并用周期图法和Welch法分别绘制信号的功率谱。再次通过根升余弦滤波器后用stem函数绘图。
(A set of values ​ ​ is+ /-1 random sequence inserted between every two data 3 0, then the sequence through a root raised cosine filter designed, periodogram and Welch method to draw the signal powerspectrum. Stem function by root raised cosine filter with drawing again.)