滤波器的参数取值问题
想问一下，=butter(n,wn,'high')中滤波器阶数n如何确定？归一化截止频率wn怎么求的？对一个具体问题，这些参数怎么取才合适？
以前没接触过这些问题，做大论文急用啊，在线等！ 本帖最后由 ljelly 于 2010-11-24 17:22 编辑
看看matlab的help中关于这个函数的使用说明，介绍的很详细
= butter(n,Wn) designs an order n lowpass digital Butterworth filter with normalized cutoff frequency Wn. It returns the filter coefficients in length n+1 row vectors b and a, with coefficients in descending powers of z.
= butter(n,Wn,'ftype') designs a highpass, lowpass, or bandstop filter, where the string 'ftype' is 'high', 'low', or 'stop',
然后再看一下给的例子，思考一下你就明白了
n = 6; Wn = /500e6;
ftype = 'bandpass';
% Transfer Function design
= butter(n,Wn,ftype);
h1=dfilt.df2(b,a); % This is an unstable filter.
% Zero-Pole-Gain design
= butter(n,Wn,ftype);
=zp2sos(z,p,k);
h2=dfilt.df2sos(sos,g);
% Plot and compare the results
hfvt=fvtool(h1,h2,'FrequencyScale','log');
legend(hfvt,'TF Design','ZPK Design') 那在具体问题中阶数n取多少合适呢？ 数字信号处理课本中都有讲的啊，通过一个式子计算出来的！
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