中文说明：
设计IIR数字陷波器，采样率为6.4kHz，陷波频率点为50Hz、150Hz、250Hz；c1.mat为输入数据文件；并且包括陷波前后的频谱分析。
English Description：
IIR digital notch filter is designed, the sampling rate is 6.4khz, the notch frequency points are 50Hz, 150Hz, 250Hz; c1.mat is the input data file; and the spectrum analysis before and after notch is included.