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HDB3.m
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HDB3.m
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%High Density bipolar 3-zeros(HDB3) :
clc; %clear command line
clear all; %clear variables
close all; %clear figures
%bits = [1 1 0 0 0 0 1 0 0 0 0 0 0 0 0];
bits = [1 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0];
%Modulation :
bitRate = 1;
voltage = 5;
samplingRate = 1000;
samplingTime = 1/samplingRate;
endTime = length(bits)/bitRate;
time = 0:samplingTime:endTime;
modulation = zeros(1,length(time));
lastbit = -voltage;
pulse = 0;
cnt = 0;
for i = 1:length(bits)
if(bits(i)==0)
cnt = cnt+1;
if(cnt==4)
if(mod(pulse,2)==0)
modulation((i-1-3)*samplingRate+1:(i-3)*samplingRate) = -lastbit;
modulation((i-1-2)*samplingRate+1:(i-2)*samplingRate) = 0;
modulation((i-1-1)*samplingRate+1:(i-1)*samplingRate) = 0;
modulation((i-1-0)*samplingRate+1:(i-0)*samplingRate) = -lastbit;
lastbit=-lastbit;
pulse =0;
cnt=0;
else
modulation((i-1-3)*samplingRate+1:(i-3)*samplingRate) = 0;
modulation((i-1-2)*samplingRate+1:(i-2)*samplingRate) = 0;
modulation((i-1-1)*samplingRate+1:(i-1)*samplingRate) = 0;
modulation((i-1-0)*samplingRate+1:(i-0)*samplingRate) = lastbit;
pulse =0;
cnt=0;
end
end
else
modulation((i-1)*samplingRate+1:(i+0)*samplingRate)=-lastbit;
lastbit=-lastbit;
pulse = pulse+1;
cnt=0;
end
end
plot(time,modulation,'LineWidth',3);
axis([0 endTime -voltage-5 voltage+5]);
%ay= gca;
%ay.XGrid = 'on';
%ay.GridLineStyle = '--';
grid on;
%Demodulation :
cnt = 0;
lastbit = -voltage;
for i = 1:length(time)
if (time(i)>cnt)
cnt = cnt + 1;
if (modulation(i)==lastbit)
demodulation(cnt-3:cnt) = 0;
else
if(modulation(i)==0)
demodulation(cnt) = 0;
else
demodulaiton(cnt) = 1;
lastbit = -lastbit;
end
end
end
end
disp('HDB3 Decoding:');
disp(demodulation);