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- [xn] = audioread('eric.wav');
- fs = 48000;
- nf=1024;
- Y = fft(xn);
- f = fs/2*linspace(0,1,nf/2+1);
- plot(f,abs(Y(1:nf/2+1)));
- d = designfilt('lowpassfir' , 'FilterOrder' , 8 ,'CutoffFrequency' , 4000 , 'SampleRate' , fs);
- filteredf = filter (d, Y);
- filteredt = ifft (filteredf);
- player = audioplayer(filteredf,fs);
- play(player);
- Fc = 100000;
- Fm = 500000;
- [p,q]=rat(fs/Fm);
- filtere=resample(filteredf,p,q);
- len = length(x);
- t = 0: 1/Fm :1;
- x = cos(2*pi*Fc*t);
- filte = fft(filtere);
- z = times(filte , x) ;
- demod = z.*cos(2*pi*Fc*t);
- [b,a] = butter(5,Fc*2/Fm);
- demod = filtfilt(b,a,demod);
- z1= awgn(z , 0 ,'measured');
- demod1 = z1.*cos(2*pi*Fc*t);
- [b,a] = butter(5,Fc*2/Fm);
- demod1 = filtfilt(b,a,demod1);
- z2= awgn(z , 10 ,'measured');
- demod2 = z2.*cos(2*pi*Fc*t);
- [b,a] = butter(5,Fc*2/Fm);
- demod2 = filtfilt(b,a,demod2);
- z3 = awgn(z ,30 ,'measured');
- demod3 = z3.*cos(2*pi*Fc*t);
- [b,a] = butter(5,Fc*2/Fm);
- demod3 = filtfilt(b,a,demod3);
- z1f = fft(z1);
- z2f = fft(z2);
- z3f = fft(z3);
- plot(z1f);title('SNR =0 in frequency');
- plot(z2f);title('SNR =10 in frequency');
- plot(z3f);title('SNR =30 in frequency');
- plot(z1);title('SNR =0 in time');
- plot(z2);title('SNR =10 in time');
- plot(z3);title('SNR =30 in time');
- [p1,q1]=rat(Fm/fs);
- z1fs=resample(z1f,p1,q1);
- z2fs=resample(z2f,p1,q1);
- z3fs=resample(z3f,p1,q1);
- sound(z1fs,fs);
- sound(z2fs,fs);
- sound(z3fs,fs);
- fc2 = 100100 ;
- z4= awgn(z , 10 ,'measured');
- demod4 = z2.*cos(2*pi*fc2*t);
- [b,a] = butter(5,fc2*2/Fm);
- demod4 = filtfilt(b,a,demod4);
- z5= awgn(z , 10 ,'measured');
- demod5 = z2.*cos(2*pi*fc*t+20);
- [b,a] = butter(5,fc*2/Fm);
- demod5 = filtfilt(b,a,demod5);
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