这是之前用到的几个简单的滤波器的程序，滤波器的设计比较简单。可以直接使用matlab里的FDA，导出滤波器系数即可。

再就是参考数字信号处理课本里面三种滤波器设计的方法，由过渡带和所选的窗函数推导出滤波器阶数，进一步根据firl和filter函数编写-This is a few simple filters used before the program, the filter design is relatively simple. You can directly use the FDA in the matlab, export filter coefficients can be.

And then refer to the digital signal processing textbook inside the three filter design method, by the transition zone and the selected window function derived filter order, and further according to firl and filter function