57 lines
906 B
Mathematica
57 lines
906 B
Mathematica
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#d = [ 1 0 1 0 1 0 0 1 0 1 1 ];
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datalen = 30;
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d = rand(1,datalen) < 0.5;
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n = 0:datalen-1;
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Tb = 0.2;
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fa = 2000;
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freq = [ 50 30 ];
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signallen = (datalen*Tb-1/fa)
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t = 0:(1/fa):signallen;
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f = freq(d(floor(t/Tb)+1)+1);
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phi = cumsum(2*pi*f)/fa;
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s = cos(phi);
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subplot(4,1,1)
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stem(n,d)
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subplot(4,1,2)
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plot(t,s)
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axis([0 signallen -1 1])
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[b,a] = butter(5,2*mean(freq)/fa);
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slow = filter(b,a,s);
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st = abs(slow);
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[b2,a2] = butter(10,2*(min(freq)*0.8)/fa);
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hk = filter(b2,a2,st);
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subplot(4,1,3)
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cla; hold on;
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plot(t,slow,'k')
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plot(t,st,'g')
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plot(t,hk,'r')
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hold off
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axis([0 signallen -1 1])
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mt = zeros(size(n));
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for i = 1:datalen
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ts = (i-1) * Tb;
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te = i * Tb;
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tf = t > ts & t < te;
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mt(i) = mean(hk(tf));
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endfor
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hold on;
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stem((n+0.5)*Tb,mt,'r');
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hold off;
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thr = (min(mt) + max(mt)) / 2;
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ds = mt > thr;
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subplot(4,1,4)
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err = ds != d;
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cla; hold on;
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stem(n(~err),ds(~err))
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stem(n(err),ds(err),'rx')
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hold off;
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