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Analog Modulation Technique:DSB-SC



01 Apr 2013 (Updated )

Calculates & Plots the Waveform for the DSB-SC Modulated Signal.

% Double-Sideband Suppressed-Carrier Transmission (DSB-SC):
% Transmission in which:
% (a) frequencies produced by amplitude modulation are symmetrically spaced above and below the carrier frequency and 
% (b) The carrier level is reduced to the lowest practical level, ideally completely suppressed.
% In the double-sideband suppressed-carrier transmission (DSB-SC) modulation, unlike AM, the wave carrier is not transmitted; 
% thus, a great percentage of power that is dedicated to it is distributed between the sidebands, which implies an increase of the cover in DSB-SC, 
% compared to AM, for the same power used.
% DSB-SC transmission is a special case of Double-sideband reduced carrier transmission.

clear all;
Message_Signal_Amplitude = input ('Enter the message signal amplitude = ');
Carrier_Signal_Amplitude = input ('Enter the carrier signal amplitude = ');
fm = input ('Enter the message frequency = ');
fc = input ('Enter the carrier frequency = ');
m = Message_Signal_Amplitude/Carrier_Signal_Amplitude;

% Representation of the Message Signal
t = 0:0.001:1;
Message_Signal = Message_Signal_Amplitude*sin (2*pi*fm*t);
subplot (3,1,1);
plot (t,Message_Signal,'b');
xlabel ('Time ---->');
ylabel ('Amplitude ---->');
title ('Message Signal ---->');
legend ('Message Signal ---->');

% Representation of the Carrier Signal
Carrier_Signal = sin (2*pi*fc*t);
subplot (3,1,2);
plot (t,Carrier_Signal,'r');
xlabel ('Time ---->');
ylabel ('Amplitude ---->');
title ('Carrier Signal ---->');
legend ('Carrier Signal ---->');

% Representation of the DSBSC Signal
DSBSC_Signal=Carrier_Signal_Amplitude*m.*sin (2*pi*fm*t).*sin (2*pi*fc*t)
subplot (3,1,3);
plot (t,DSBSC_Signal,'black');
xlabel ('Time ---->');
ylabel ('Amplitude ---->');
title ('Double Sideband Suppressed Carrier Wave ---->');
legend ('DSB-SC Signal ---->');

% Add title to the Overall Plot
ha = axes ('Position',[0 0 1 1],'Xlim',[0 1],'Ylim',[0 1],'Box','off','Visible','off','Units','normalized', 'clipping' , 'off');
text (0.5, 1,'\bf Analog Modulation Technique: Double Sideband Suppressed-Carrier Transmission (DSB-SC)','HorizontalAlignment','center','VerticalAlignment', 'top')

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