Digital Butterworth Filter Design

MATLAB语句： [b,a]=butter(n,wn,’ftype’)

A design order is n, the cutoff frequency of the digital low pass filter wn. If the parameter ftype take 'high' or 'stop', is used to design the respective high pass or band-stop filter. The return value of a and b coefficients of the numerator and denominator of the system function.

Example: Design of an order for the order of 9, the cutoff frequency of 300Hz Butterworth high-pass filter, the sampling frequency is 1000. And plot its frequency characteristics.

Program: n = 9;

             wn=300/500;

             [b,a]=butter(n,wn,’high’);

             freqz(b,a,128,1000);

Author: TianSL