Code covered by the BSD License

# Analog Modulation Technique:AM

Calculates & Plots the Waveform for the Amplitude Modulated Signal

AM_Modulation_Technique.m
% Theory:
%
% Amplitude modulation (AM):
% It is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave.
% AM works by varying the strength of the transmitted signal in relation to the information being sent. For example, changes
% in signal strength may be used to specify the sounds to be reproduced by a loudspeaker, or the light intensity of television
% pixels.
% In radio communication, a continuous wave radio-frequency signal (a sinusoidal carrier wave) has its amplitude modulated by an
% audio waveform before transmission. The audio waveform modifies the amplitude of the carrier wave and determines the envelope of
% the waveform. In the frequency domain, amplitude modulation produces a signal with power concentrated at the carrier frequency and
% two adjacent sidebands. Each sideband is equal in bandwidth to that of the modulating signal, and is a mirror image of the other.
% Amplitude modulation resulting in two sidebands and a carrier is called "double-sideband amplitude modulation" (DSB-AM). Amplitude
% modulation is inefficient in power usage; at least two-thirds of the power is concentrated in the carrier signal, which carries no
% useful information (beyond the fact that a signal is present).
% To increase transmitter efficiency, the carrier may be suppressed. This produces a reduced-carrier transmission, or
% DSB "double-sideband suppressed-carrier" (DSB-SC) signal. A suppressed-carrier AM signal is three times more power-efficient than AM.
% If the carrier is only partially suppressed, a double-sideband reduced-carrier (DSBRC) signal results. For reception, a local oscillator
% will typically restore the suppressed carrier so the signal can be demodulated with a product detector.

clc;
clear all;
t = 0:0.001:1;
Message_Signal_Amplitude = input('Enter the Amplitude of Message Signal = ');
Carrier_Signal_Amplitude = input('Enter the Amplitude of Carrier Signal = ');
Message_Signal_Frequency = input('Enter the Message Frequency = ');
Carrier_Signal_Frequency = input('Enter the Carrier Frequency = ');
m = Message_Signal_Amplitude/Carrier_Signal_Amplitude;

% Representation of the Message Signal
sm = Message_Signal_Amplitude.*sin(2*pi*Message_Signal_Frequency*t);
subplot(3,1,1);
plot(t,sm,'b');
xlabel('Time ---->');
ylabel('Amplitude ---->');
title('Message Signal---->');
legend('Message Signal ---->');
grid on;

% Representation of the Carrier Signal
sc = Carrier_Signal_Amplitude.*sin(2*pi*Carrier_Signal_Frequency*t);
subplot(3,1,2);
plot(t,sc,'black');
xlabel('Time ---->');
ylabel('Amplitude ---->');
title('Carrier Signal');
legend('Carrier Signal ---->');
grid on;

% Representation of the AM Signal
Amplitude_Modulated_Signal = (Message_Signal_Amplitude+m*Message_Signal_Amplitude.*sin(2*pi*Message_Signal_Frequency*t)).*sin(2*pi*Carrier_Signal_Frequency*t)
subplot(3,1,3);
plot(t,Amplitude_Modulated_Signal,'red');
xlabel('Time ---->');
ylabel('Amplitude ---->');
title('Amplitude Modulated Wave ---->');
legend('AM Signal ---->');
grid on;

% 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: Amplitude Modulation (AM)','HorizontalAlignment','center','VerticalAlignment', 'top')