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FOSSEE_Communication_Systems_Toolbox >> FOSSEE_Communication_Systems_Toolbox > ssbdemod

ssbdemod

This function performs Single Side Band Amplitude Demodulation

Description

Z = SSBDEMOD(Y,Fc,Fs) demodulates the single sideband amplitude modulated signal Y with the carrier frequency Fc (Hz). Sample frequency Fs (Hz). zero initial phase (ini_phase). The modulated signal can be an upper or lower sideband signal. A lowpass butterworth filter is used in the demodulation.

Z = SSBDEMOD(Y,Fc,Fs,INI_PHASE) adds an extra argument the initial phase (rad) of the modulated signal.

Z = SSBDEMOD(Y,Fc,Fs,INI_PHASE,NUM,DEN) adds extra arguments about the filter specifications i.e., the numerator and denominator of the lowpass filter.

Fs must satisfy Fs >2*(Fc + BW), where BW is the bandwidth of the modulating signal.

Examples

Fs =200;
t = [0:2*Fs+1]'/Fs;
ini_phase = 5;
Fc = 20;
fm1= 2;
fm2= 3
x =sin(2*fm1*%pi*t)+sin(2*fm2*%pi*t);
y = ssbmod(x,Fc,Fs,ini_phase);
o = ssbdemod(y,Fc,Fs,ini_phase);
z = fft(y);
zz =abs(z(1:length(z)/2+1 ));
axis = (0:Fs/length(zz):Fs -(Fs/length(zz)))/2;

figure
subplot(3,1,1); plot(x);
title(' Message signal');
subplot(3,1,2); plot(y);
title('Amplitude modulated signal');
subplot(3,1,3); plot(axis,zz);
title('Spectrum of amplitude modulated signal');
z1 =fft(o);
zz1 =abs(z1(1:length(z1)/2+1 ));
axis = (0:Fs/length(zz1):Fs -(Fs/length(zz1)))/2;
figure
subplot(3,1,1); plot(y);
title(' Modulated signal');
subplot(3,1,2); plot(o);
title('Demodulated signal');
subplot(3,1,3); plot(axis,zz1);
title('Spectrum of Demodulated signal');

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