关于巴特沃斯低通滤波器

在[B,A]=butter(n,wn)中，n是滤波器的阶数，Wn是截止频率，Wc = 截止频率*2/采样频率

Wc=2*50/Fs;                                          %截止频率 50Hz
[b,a]=butter(4,Wc，‘low’);  %低通滤波器  主要去除高频信号，可消除白噪声等
Signal_Filter=filter(b,a,Mix_Signal_1);

[b,a]=butter(4,Wc，‘high’);  %高通滤波器 主要去除低频信号，可消除基线漂移等

[b,a]=butter(4,Wc，‘stop’);  %带阻滤波器  

[b,a]=butter(4,Wc);  %带通滤波器 Wc=[W1 W2]  W1<W2

仍有问题可 help butter ：

The cutoff frequency Wn must be 0.0 < Wn < 1.0, with 1.0 corresponding to
half the sample rate.

If Wn is a two-element vector, Wn = [W1 W2], butter returns an
order 2N bandpass filter with passband W1 < W < W2.
[B,A] = butter(N,Wn,'high') designs a highpass filter.
[B,A] = butter(N,Wn,'low') designs a lowpass filter.
[B,A] = butter(N,Wn,'stop') is a bandstop filter if Wn = [W1 W2].