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FSK.m
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FSK.m
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clear all;
close all;
clc;
bits = [1 0 1 0 1 1 1 0 1 1 0 1];
bit_duration = 2;
fs = 100;
Total_time = length(bits) * bit_duration; %# time needed to send whole data
time = 0: 1/fs: Total_time;
amplitude = 2;
f1 = 2;
f0 = 0.5;
carrier_signal_forone = amplitude * sin(2 * pi * f1 * time);
carrier_signal_forzero = amplitude * sin(2 * pi * f0 * time);
%plot(time, carrier_signal);
idx = 1;
modulated_carrier_signal = [];
for i = 1 : length(time)
if bits(idx) == 1
modulated_carrier_signal(i) = carrier_signal_forone(i);
else
modulated_carrier_signal(i) = carrier_signal_forzero(i);
end
if time(i)/bit_duration >= idx
idx = idx + 1;
end
end
%# ploting
plot(time, modulated_carrier_signal);
xticks([0: bit_duration: Total_time]);
yticks([-amplitude-2: 2: amplitude+2]);
ylim([-amplitude-2, amplitude+2]);
xlim([0, Total_time]);
grid on;
title("FSK");
xlabel("Time");
ylabel("Amplitude");
line ([0, Total_time], [0 0], "linestyle", "--", "color", "r");
% Top axis
ax1=gca;
ax2 = axes('Position', get(ax1, 'Position'), 'Color', 'none');
set(ax2, 'XAxisLocation', 'top');
set(ax2, 'XLim', get(ax1, 'XLim'));
set(ax2, 'YLim', get(ax1, 'YLim'));
set(ax2, 'XTick', [bit_duration/2: bit_duration: Total_time]);
set(ax2, 'YTick', [-amplitude-2: 2: amplitude+2]);
set(ax2, 'XTickLabel', bits);
%set(ax2, 'XLabel', 'Data bits');
%Demodulation
demodulated = [];
idx = 1;
for i = 1 : length(time)
if time(i)/bit_duration >= idx
data = modulated_carrier_signal(i);
if data == carrier_signal_forone(i)
demodulated(idx) = 1;
else
demodulated(idx) = 0;
end
idx = idx + 1;
end
end
disp("Orginal bits:");
disp(bits);
disp("Demodulation:");
disp(demodulated);