chapter_4_1_mod_types.m

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Sending binary data via sinusoidal signal manipulation

% Parameters
sig_len = 1000; % Signal length (in samples)
sampl_per_bin = 100; % Samples per binary representation
bin_data_len = sig_len/sampl_per_bin; %length of binary stream is a multiple of signal length
bin_data = round(rand(1,bin_data_len));

sig_carrier_base = sin(2*pi*(0:(1/sampl_per_bin):(1-(1/sampl_per_bin)))); % Baseline carrier
sig_carrier_freq = sin(2*2*pi*(0:(1/sampl_per_bin):(1-(1/sampl_per_bin)))); % Double frequency
sig_carrier_phase = sin(2*pi*(0:(1/sampl_per_bin):(1-(1/sampl_per_bin)))+(pi/4)); % Phase shifted by 45 degrees

% Modulate sinusoidal carrier via amplitude, phase, and frequency
% manipulations
sig_bin = []; % Binary waveform
sig_ask = []; % Amplitude modulated
sig_psk = []; % Phase modulated
sig_fsk = []; % Frequency modulated
for ind = 1:1:bin_data_len
    if (bin_data(ind)==1)
        sig_bin = [sig_bin ones(1,sampl_per_bin)];
        sig_ask = [sig_ask sig_carrier_base];
        sig_psk = [sig_psk sig_carrier_base];
        sig_fsk = [sig_fsk sig_carrier_base];
    else
        sig_bin = [sig_bin zeros(1,sampl_per_bin)];
        sig_ask = [sig_ask 0.5*sig_carrier_base];
        sig_psk = [sig_psk sig_carrier_phase];
        sig_fsk = [sig_fsk sig_carrier_freq];
    end
end

figure;
subplot(4,1,1);
plot(sig_bin);
title("Binary Signal");

subplot(4,1,2);
plot(sig_ask);
title("ASK (Amplitude Shifting) Signal");

subplot(4,1,3);
plot(sig_fsk);
title("FSK (Freq. Shifting) Signal");

subplot(4,1,4);
plot(sig_psk);
title("PSK (Phase Shifting) Signal");