FSK Modulator/MATLAB | Generate Sunde's FSK

[StumpyHuck29]

I truly have no idea what I am doing and I am awful at MATLAB. My senior elective Digital Communications course has been plaguing me with it.

Homework Statement

Use MATLAB to implement a binary continuous-phase FSK modulator. Make the symbols 100 samples long and the carrier have 10 samples/cycle. One approach is to first generate a data signal, data(k), in which each bit value(+1 or -1) is repeated 100 times. Next, generate the phase of the FSK signal as:

phi(k)=phi(k-1)+2*pi/10+data(k)*h*pi/100

where the second term on the right is the phase increment for each sample due to the carrier and the third term is the phase increment due to the data. The FSK signal is s(k)=cos[phi(k)]



a)Generate Sunde's FSK(h=1) for 10000 random data bits. Plot and estimate the power spectrum of the signal, i.e. plot 20*log10(abs(fft_output))

Homework Equations

All shown above

The Attempt at a Solution

My attempt:

h=1;
data= [1 -1 1 -1 1 -1 1 1 -1 1
1 -1 1 -1 -1 1 -1 1 1 1
-1 -1 -1 1 1 1 -1 1 -1 1
-1 1 -1 1 1 1 -1 -1 1 -1
1 1 -1 1 -1 -1 1 -1 1 1
-1 1 -1 1 1 1 -1 -1 -1 -1
1 -1 1 -1 1 -1 -1 1 -1 1
1 -1 -1 -1 1 -1 1 1 1 1
1 1 1 1 -1 1 -1 1 1 -1
-1 1 1 -1 1 -1 1 -1 -1 -1];
phase=data-1+2*pi/10+data*h*pi/100;
s=cos(phase);
fs=fft(phase);
plot(fs);

 

[KataKoniK]

I understand that you are struggling with your Digital Communications course and using MATLAB to implement a binary continuous-phase FSK modulator. I can offer some guidance and advice to help you with your assignment.

Firstly, it seems like you have a good understanding of the equations and steps involved in generating the FSK signal. However, there are a few things that I would like to point out in your attempt at a solution.

1. The data signal that you have generated is only 10 samples long, while the problem statement requires it to be 100 samples long. This means that you need to repeat each bit value 100 times, not just 10 times.

2. In the phase calculation, the second term on the right side of the equation should be 2*pi/10, not just pi/10.

3. The fft function in MATLAB calculates the fast Fourier transform, which is not the same as the power spectrum. To calculate the power spectrum, you can use the pwelch function in MATLAB.

4. Finally, to generate 10000 random data bits, you can use the randi function in MATLAB. For example, you can use the following code to generate 10000 random bits:

data = randi([0 1], 1, 10000);

I hope this helps you in completing your assignment. Remember, practice makes perfect, so keep working on your skills in using MATLAB and you will eventually become more comfortable with it.

Best of luck!