Earlier I wrote a matlab script to modulate and demodulate an am radio wave and make a .wav file. I did it with a matlab script and it worked alright.

close all;
clear all;
fs = 2e6;
t = [0:1/fs:5];

f_cut_off1 = 10000;
f_cut_off2 = 10;
f = 2000;                                        %input frequency
fc = 940e3;                                     %carrier frequency

k = length(t);

    
input_sig = (0.2)*cos(2 * pi * f * t);                %input signal

wavwrite(input_sig,fs,32,'input_sig');

carrier_sig = (0.5)*cos( 2 * pi * fc * t);            %carrier signal



mod_sig = input_sig .* carrier_sig + carrier_sig;  %modulated signal


                                       %interval to randonize noise
noise = rand(1, k) - .5;                    %random nosie

new_mod = mod_sig + noise;          % mod signal + noise


%Apply HW Rectifier


for i = 1:k
if new_mod(i) <= 0
    x(i) = 0;
else
    x(i) = new_mod(i);
end
end



rc1 = 1 / (2 * pi * f_cut_off1);
rc2 =  1 / (2 * pi * f_cut_off2);

%Apply Low Pass Filter
num2 = [0    1];
den2 = [rc1   1];
subplot(324), bode(num2, den2)

sys2 = tf(num2, den2);

lpf = lsim(sys2, x, t);




%Apply High Pass Filter    

num1 = [rc2  0];
den1 = [rc2 1];


sys1 = tf(num1, den1);

hpf = lsim(sys1, lpf, t);

vout = hpf;

%Apply Convolution
g = 20;
h = (1 / g) * ones(1, g);

y = conv(h ,vout);



wavwrite(y,fs,32,'vout')

Now I'm trying to do the same thing, but I'm calling simulink from a script. The problem I'm having is that I'm only getting a 48 byte wav file at the end of my script. In my first script my wav file was 40Mb. Is anyone here familiar with simulink? Here's my code. I can put my simulink model up if necessary.

clear all
clc
fs = 2e6;
t = [0:1/fs:5];
t = t';
f_cut_off1 = 10000;
f_cut_off2 = 10;
f = 2000;                                        %input frequency
fc = 940e3;                                      %carrier frequency

%k = 1;%length(t);

rc1 = 1 / (2 * pi * f_cut_off1);
rc2 =  1 / (2 * pi * f_cut_off2);

input_sig = 1*cos(2 * pi * f * t);                %input signal
input_sig1 = [t'; input_sig'];
save('input_sig1.mat', 'input_sig1');

carrier_sig = 1*cos( 2 * pi * fc * t);        %carrier signal
carrier_sig1 = [t' ; carrier_sig'];
save('carrier_sig1.mat', 'carrier_sig1');

load_system('am_mod_simulinkORIGINAL');

set_param('am_mod_simulinkORIGINAL','Stoptime',num2str(t(size(t,1),1)));

set_param('am_mod_simulinkORIGINAL/LPF', 'Numerator', '[0 1]');
den1 = strcat('[',num2str(rc1),',','1',']')
set_param('am_mod_simulinkORIGINAL/LPF', 'Denominator', den1);
den2 = strcat('[',num2str(rc2),',','1',']')
set_param('am_mod_simulinkORIGINAL/HPF', 'Denominator', den2);
num2 = strcat('[',num2str(rc2),',','0',']')
set_param('am_mod_simulinkORIGINAL/HPF', 'Numerator', num2);


save_system('am_mod_simulinkORIGINAL');

sim('am_mod_simulinkORIGINAL');

p = load('outputsignal.mat');

data = p.ans;

g=20;
h = (1 / g) * ones(1, g);
y = conv(h ,data(2,:));

wavwrite('y',fs,32,'out_sig');

 

Not sure, but you may need to set a simulation time for Simulink from your script.

Is the 48 bytes relevant data?

 

48 bytes will be header plus 4 bytes with "data" https://ccrma.stanford.edu/courses/422/projects/WaveFormat/

 

So do the 4 bytes correlate with your expected results? There may not be enough data to determine that though...

 

I got it to work. Instead of doing data = p.ans, I did data = ans. That seemed to do the trick.

 

I got it to work. Instead of doing data = p.ans, I did data = ans. That seemed to do the trick.

By that solution, making data = p, should also work...