Vestigal side band matlab code

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ong jia eek
ong jia eek on 19 Oct 2019
Answered: MD Rasel Basunia on 8 Apr 2022
%>>>>>>>>>>>>>>>>>>>> Tuterial on AM vestigial sideband Modulation <<<<<<<<<<<<<<<<<<<<<<<<<<
clc;
close all;
clear all;
%XXXXXXXXXXXXXXXXXXXXXXXXXXX Define AM modulation Index XXXXXXXXXXXXXXXXXXX
disp(' example: m=1 means 100% modulation');
m=input(' Enter the value of modulation index (m) = ');
%m=1; % for 100% modulation
if (0>m||m>1)
error('m may be less than or equal to one and greater0 than to zero');
end
%XXXXXXXXXXXXXXXXX modulating signal generation XXXXXXXXXXXXXXXXXXXXXXXXXX
Am =input('Enter the value of amplitude modulation =');
n=input('Enter number of cycles = '); % input for number of modulationd signal cycles
%Am=5; % Amplitude of modulating signal
fa=2000; % Frequency of modulating signal
Ta=1/fa; % Time period of modulating signal
t=0:Ta/999:n*Ta; % Total time for simulation
ym=Am*sin(2*pi*fa*t); % Equation of modulating signal
figure(1)
subplot(3,1,1);
plot(t,ym), grid on;% Graphical representation of Modulating signal
%axis ([0 1 -5 5]);
title ( ' Modulating Signal ');
xlabel ( ' time(sec) ');
ylabel (' Amplitud(volt) ');
%XXXXXXXXXXXXXXXXXXXXX carrier signal generation XXXXXXXXXXXXXXXXXXXXXXXXXX
Ac=Am/m;% Amplitude of carrier signal [ where, modulation Index (m)=Am/Ac ]
fc=fa*10;% Frequency of carrier signal
Tc=1/fc;% Time period of carrier signal
yc=Ac*sin(2*pi*fc*t);% Eqation of carrier signal
subplot(3,1,2);
plot(t,yc), grid on;% Graphical representation of carrier signal
title ( ' Carrier Signal ');
xlabel ( ' time(sec) ');
ylabel (' Amplitud(volt) ');
%XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX AM Modulation XXXXXXXXXXXXXXXXXXXXXXXXXXXXX
y=Ac*(1+m*sin(2*pi*fa*t)).*sin(2*pi*fc*t)(; % Equation of Amplitude
%modulated signal
subplot(3,1,3);
plot(t,y);% Graphical representation of AM signal
title ( ' Amplitude Modulated signal ');
xlabel ( ' time(sec) ');
ylabel (' Amplitud(volt) ');
grid on;
%>>>>>>>>>>>>>>>>>>>>>> end of program <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
How to change this matlab code to vestigial side band?
How can we put frequency code here?
  1 Comment
dhanvanth voona
dhanvanth voona on 21 May 2021
this is only amplitude modulation, we need to design appropriate filters and apply them to message signals to obtain VSB

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Answers (1)

MD Rasel Basunia
MD Rasel Basunia on 8 Apr 2022
%% message signal m(t)=u(t+2)-u(t-2)
syms t f
fc=10;%let carrier frequency frequency contain 10 Hz .x_carrier=cos(2*pi*10*t)
x = heaviside(t+2)- heaviside(t-2) %% Fourier transform of m(t)
X=fourier(x,f) ;% fourier transform
%% using anonymous function
XX = @(f) 2*(sin(2*f)./(f))
f=[-100:0.01:100-0.01];% proper frequency range .Avoiding 0 / 0.
%% Generation of DSB-SC
Xshift=( XX(f-fc)+XX(f+fc));
%% Designing VSB shaping filter characteristic
% Define normalized VSB shaping filter
Hf = @(f) ((f>=9 & f<=20)) ;
%% Generating SSB
SSB =@(f) Xshift.*(f>=10 & f<=50) + Xshift.*(f<=-10 & f>=-50);
%%Here I am just plotting SSB-SC and VSB modulation signals.you can also
%%plot Hf(f) characteristic normalized filter and DSB-SC from equation.
%% Generation of VSB
VSB_upper = @(f)((XX(f-fm)+XX(f+fm)).*Hf(f)) %SSB(f).*Hf(f)SB_upper = @(f)((XX(f-fm)+XX(f+fm)).*Hf(f)) %SSB(f).*Hf(f)
subplot(211)
%% ploting SSB
plot(f,abs(SSB(f)),[-10,-10],[0,4],[10 10],[0,4],'r','linewidth',1.5);
% set axis for visualize porpuse only
xlim([-35 35]);
grid on;ylim([0 6]);xlabel('frequency in Hz');ylabel('Magnitude spectrum');
legend('| SSB-SC|');
title('Single Sideband Modulation');
%% ploting VSB
subplot(212)
plot(f,abs(VSB_upper(f)),'b',-f,abs(VSB_upper(f)),'k','linewidth',1.5);grid on;
xlabel('frequency in Hz');ylabel('Magnitude spectrum');
title('SSB');ylim([0 6]);legend('| VSB |');
% set axis for visualize purpose
xlim([-35 35]);
% see carefully around 10 Hz .A vestige was found before +10 Hz and also in
% case negative -10 Hz

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