stufilnoise.m

信号被白噪声干扰

%filter test
%generate signal
fs = 100;
t = 0:1/fs:1;
noise = randn(1,length(t));
s = sin(2*pi*t*5)+sin(2*pi*t*15)+sin(2*pi*t*30);%0.5*noise;
%a = 1; % FIR filter
%b = Num; % from FDAtool
b = [-4.9537e-018 -0.0088982 0.010813	0.056032	0.069341	-2.0882e-017...
    -0.11389	-0.15675	-0.056777	0.11511	0.2	0.11511	-0.056777	-0.15675...
    -0.11389	-2.0882e-017	0.069341	0.056032	0.010813	-0.0088982	-4.9537e-018];
sf = fftfilt(b,s);
% compare two spectrum
SS = fft(s,512);
ASS = abs(SS)/fs;
SFF = fft(sf,512);
ASFF = abs(SFF)/fs;
deltaF = fs*(0:255)/512;
figure(1);
subplot(221);
plot(t,s);
subplot(223);
plot(deltaF,ASS(1:256));
subplot(222);
plot(t,sf);
subplot(224);
plot(deltaF,ASFF(1:256));