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## MSK matlab code | MSK modulation matlab source code

This page of MATLAB source code covers MSK matlab code. The output plots and mathematical equations of MSK modulation matlab code are mentioned. MSK modulation stands for Minimum Shift Keying Modulation.

Introduction:
MSK modulation is derived from OQPSK modulation. OQPSK offers maximum pahse shift of 45 degree between two transitions. MSK offers 0 degree phase shift between transitions. MSK modulation uses half cycle sine wave instead of rectangular pulse wave. In MSK, frequency of logic-0 and logic-1 differs by half of data rate. MSK equation and modulation waveforms are depicted below. Fig.1 MSK Equation Fig.2 MSK modulation for NRZ data signal in time domain

Refer MSK versus GMSK>> which explains time domain waveforms of MSK and GMSK modulation types with their respective mathematical equations.

### MSK matlab code

clear;
clc;
b = input('Enter the Bit stream \n '); %b = [0 1 0 1 1 1 0];
n = length(b);
t = 0:.01:n;
x = 1:1:(n+2)*100;
for i = 1:n
if (b(i) == 0)
b_p(i) = -1;
else
b_p(i) = 1;
end
for j = i:.1:i+1
bw(x(i*100:(i+1)*100)) = b_p(i);
if (mod(i,2) == 0)
bow(x(i*100:(i+1)*100)) = b_p(i);
bow(x((i+1)*100:(i+2)*100)) = b_p(i);
else
bew(x(i*100:(i+1)*100)) = b_p(i);
bew(x((i+1)*100:(i+2)*100)) = b_p(i);
end
if (mod(n,2)~= 0)
bow(x(n*100:(n+1)*100)) = -1;
bow(x((n+1)*100:(n+2)*100)) = -1;
end
end
end
bw = bw(100:end);
bew = bew(100:(n+1)*100);
bow = bow(200:(n+2)*100);
wot = 2*pi*t*(5/4);
Wt = 2*pi*t/(4*1);
st = bow.*sin(wot+(bew.*bow).*Wt);
subplot(4,1,1)
plot(t,bw)
grid on ; axis([0 n -2 +2])
subplot(4,1,2)
plot(t,bow)
grid on ; axis([0 n -2 +2])
subplot(4,1,3)
plot(t,bew)
grid on ; axis([0 n -2 +2])
subplot(4,1,4)
plot(t,st)
grid on ; axis([0 n -2 +2])
Fs=5/4; %figure
%periodogram(st)
S = fft(st,65);
PSS = S.* conj(S) / 65;
f = 1000*(-16:16)/65;
figure
plot(f,PSS(1:33))

### Input and Output of MSK modulation matlab source code

Run the downloaded MSKModulation.m file after unzipping the folder. and provide input as follows. After the input is given press "ENTER" key, you will get output matlab image as below. 