带通滤波器的函数程序，可以直接调用，用于需要滤波器的各种场合-Functional programs band-pass filter, can be called directly, for a variety of applications requiring filters

Matlab 常用fft包bandp， hua_fft源程序，非常好用(Matlab commonly used FFT package bandp, hua_fft source code, very easy to use)