### MATLAB >> frequency modulation simulation in matlab

i an doing an electronics project and would like to use matlab to
simulate what my hard ware is doing
basically what im doing is frequency modulating a sound wave onto the
mains 220v 50hz signal and transmitting it then the other end
recieving the 220v 50 hz signal and demodulating it to extract the
sound wave any tips on where i should look or some sample code would
be great i have little to know background to matlab so any help would
be greatly appreciated
cheers
Eoin F

```HEllo All,
I am having one querry regarding MATLAB.

What I would be doing is that I will give the signal from a microphone
and I have to use MATLAB so that the signal gets frequency modulated
and then I will be taking the output from the headphone jack and mix it
with a carrier frequency [Local Oscillator] and send it to the spectrum
analyzer.I am doing a project named (Software Radio) where you have to
do the signal modulation using Software
So could some one help with the code I have written below
it is giving the error.

??? Error using ==> +
Matrix dimensions must agree..
Regards
Nitin

The Code is :
Fs = 8000;% Sample Rate is 22050 Hz
set (AI, 'SampleRate', Fs)
d = 10;           % 10 second acquisition
set(AI, 'SamplesPerTrigger', d*Fs);
start (AI);
data =  getdata(AI);
n = Fs* d;
pause(5);
%plot (data);
%sound(data, Fs);
% set carrier characteristics
Fc = 1000;                     % carrier frequency (Hz)
c = (1:n) / Fs;                % carrier data preparation
c = 2 * pi * Fc * c;

% set modulator
Fm = data;                        % modulator frequency (Hz)
mi = 0.5;                      % modulator index
m = (1:n) / Fs;                % modulator data preparation
m = mi * cos(2 * pi * Fm * m); % sinusoidal modulation

% frequency modulation
s = sin(c + m);                % frequency modulation

%sound presentation
sound(s, Fs);                  % sound presentation
%pause(d + 0.5);                % wating for sound end

```

```Hello,

I'm trying to find the frequency response of a laser (20log(power_
amp_out/current_amp_in) that abide to a certain set of rate equations.

As an input I'm using a sinusoidal current above threshold, i.e: I=Idc
+Im*sin(2*pi*f*T).
For this input current I should also be getting a sinusoidal out put.
Using the rate equations I get the power vs. time for each input
current

The question is what time, T, should I use in the input current? Also,
since there are some ringing involved in the output power, should I
wait for them to settle down? won't it be a problem is higher
frequency?

Thanks.
```

```Hi,
I have a problem in using frequency hopping modulation,I used the
blutooth exemple from file exchange but I extract only the modulation
and the demodulation part and I resreve the same parameters then the
bluetooth exemple but I get this error message :
Error reported by S-function 'scomfskdemod' in 'untitled1/Frequency
hopping FM Demodulator/M-FSK Demodulator Baseband':
Input signal must be discret
The channel that I'm using is AWGN.
```

```Dear all,
We are acquiring the ECG with a high resolution system, sampling
frequency 2400Hz. The system is an oversampling sigma delta, 24 bits.

In some ECG (from normal subjects and patients) we get, added to the
ECG, a  frequency modulated version of the ECG itself, e.g. a sinus
wave with constant amplitude and whose instant frequency is
proportional to the ECG signal value in that particular time instant.
This component is not visible in the acquired ECG, and we can see it
if we perform some advanced spectral analysis. Moreover the carrier
frequency of this component is around 800Hz which looks way to high to
be due to some physiological mechanism .

Where the hell is this component coming from? Sigma-delta behavior?
Interference? (we are doing the acquisition in a  shielded room).

Your input is welcome.

Arnaldo
```