升余弦滤波器设计，产生眼图，输入调制方式为2PAM和4PAM，符号率为1Hz，等效信道滤波器为升余弦滚降成形滤波器(缺省滚降系数为0.5)-Raised cosine filter design, resulting in eye diagrams, input modulation for 2PAM and 4PAM, symbol rate of 1Hz, the equivalent channel filter for shaping raised cosine filter (default roll-off factor of 0.5)