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% Attribution-Noncommercial 2.5 India
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% http://creativecommons.org/licenses/by-nc/2.5/in/
% Author : Krishna
% Email : krishna@dsplog.com
% Version : 1.0
% Date : 18 January 2008
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% script for generting transmit waveforms in a minimum shift
% keying, a form of continuous phase frequency shift keying
clear all
close all
rand('seed',777); % initializing the random state
N = 7; % number of bits
ipBin = rand(1,N) > 0.5; % binary 0's and 1's
fs = 100;
fc = 1;
T = 1;
ts = [0:1/fs:T]; % generting the sampling instants
ts = ts(1:end-1);
tsR = kron(ones(1,N),ts);
ip = 2*ipBin-1; % converting 0's to -1, 1's to 1
% generating two frequencies corresponding to 0 and 1
% 0 --> fc - 1/4T
% 1 --> fc + 1/4T
fm = ip/(4*T);
fmR = kron(fm,ones(1,fs)); % repeating
% genertaing the phase
theta = pi/2*filter([0 1],[1 -1],ip);
thetaR = kron(theta,ones(1,fs)); % repeating
xt = cos(2*pi*(fc+fmR).*tsR + thetaR );
% plotting
subplot(3,1,1),plot(kron(ip,ones(1,fs)));
axis([0 N*fs -1.25 1.25]);grid on
subplot(3,1,2), plot(xt);
axis([0 N*fs -1 1]);grid on
subplot(3,1,3),plot(kron(mod(theta*180/pi,360),ones(1,fs)))
axis([0 N*fs -360 360]);grid on
