Objectives
How to write Matlab code that encodes a digital data into digital signal?
Study sample Matlab program for unipolar NRZ, NRZ-L, and Bipolar AMI
Program Code
Unipolar NRZ
A positive voltage represents a binary 1, and zero volts indicates a binary 0. It is the simplest line code.
% Unipolar NRZ
clc
message = [0 1 1 0 1 0 1];
data = [0 0 1 0 1 0 0 0 1 0 0 0 1 0];
i = 1 : 7;
j = 1.99 : 7.99;
time = [ ];
for k = 1 : 7
time = [time i(k), j(k)];
end
% Digital Signal Generation:
signal = [ ];
for t=1:2:13
if (data(t) == 0)
signal (t : t+1) = 0;
else
signal (t : t+1) = -1;
end
end
subplot(2,1,1);
plot (time, signal) % Plotting PCM Signal
xlabel ('Time (t)')
ylabel ('Amplitude (A)')
title('Digital Signal')
Simulation Results
NRZ-L
In this encoding schemes, 0 is represented by +ve volt and 1 is represented by negative volt.
Program Code
% NRZ-L
message = [0 1 0 1 1 1 0 0 1 1 1 1 ];
data = message;
i = 1:length(messgae);
j=1.99:length(message+0.99);
time = []
for (k = 1 : length(message))
time= [time i(k) j(k)]
end
% Generating signal
signal = [];
N = length(data);
for (t=1:2:N)
if(data(t)==1)
signal(t:t+1)=1;
else
signal(t:t+1)=-1;
end
end
% display the signal
figure(1);
plot(time,signal,'linewidth',2)
title('NRZ-LZ')
xlabel('time')
ylabel('voltage level')
axis([1 8 -0.5 1.5 ])
Simulation Results
Pseudo Ternary Encoding
A multilevel binary encoding that complements the bipolar-AMI encoding: binary 1 is represented by a lack of pulse, and a binary 0 is represented by a positive or a negative pulse. The binary 0 pulses must alternate in polarity.
Program Code
clc
message = [0 1 1 0 1 1 1 0 0 0 1];
data = zeros(1,2*length(message)-1);
data (1 : 2 : end) = message;
i = 1 : 11;
j = 1.99 : 11 + 0.99;
time = [ ];
for (k = 1 : length(message));
time = [time i(k), j(k)];
end
% Gnerating Signal
signal = [ ];
n = length(data);
prebit = 1;
for t = 1 : 2 : n
if (data(t) == 0)
signal(t : t+1) = 0;
else if (data(t) == 1 & prebit == 1)
signal (t : t+1) = 1;
prebit = -1;
else
signal (t : t+1) = -1;
prebit = 1;
end
end
end
subplot(2,1,1)
plot (time, signal) % Plotting …
title ('Digital Signal')
xlabel ('Time')
ylabel ('Amplitude')
