訊號處理除去加性噪音的乙個方法

原理：在訊號採集時，經常有工業噪音的干擾，比如打樁機引起的震動等，這裡噪音一般為高頻分量，可以利用傅利葉變換，在巴特沃斯低通濾波器下進行濾波處理，並且需要設定相應的通帶截止頻率和阻帶截止頻率。

下圖為對訊號處理後及處理前的頻域和時域分布

a = xlsread(『c:\users\legion\documents\tencent files\949800083\filerecv\mobilefile\incx_1.xlsx』,『sheet2』);

y = a( 394:end,4);

fs =1000;

t = 1/fs;

l = 42484;

t = ( 0:l-1)

t;y = fft(y,l);

n = 0:l-1;

k = nfs/l;

subplot(324);

plot(k,abs(y)/5)

title(『原頻率訊號』);

axis([0,5,0,20]);

wp = 2.1/fs;

ws = 6/fs;

[n,wn] = buttord(wp,ws,1,50);

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

[h,f] = freqz(a,b,『whole』,fs);

f = (0:length(f)-1)』*fs/length(f);

subplot(325);

plot(f(1:length(f)/2),abs(h(1:length(f)/2)));

title(『濾波器』);

axis([0,10,0,10]);

sf = filter(a,b,y);

subplot(321);

plot(t,sf);

title(『濾波後訊號』);

subplot(322);

plot(t,y);

title(『原訊號』);

sf = fft(sf);

subplot(323);

plot((1:length(sf)/2)

fs/length(sf),2abs(sf(1:length(sf)/2))/length(sf));

title(『濾波後頻率訊號』);

axis([0,1,0,1]);

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