Matlab: Analysis of signal

0
votes

I have a problem with this task:

For free route perform frequency analysis and give parametrs of each signal component:

  • time of beginning and ending of each component
  • beginning and ending frequency
  • amplitude (in time domain) in the beginning and end of each signal's component
  • level of noise in dB

Assume, that, the parametrs of each component like amplitude, frequency is changing lineary in time. Frequency of sampling is 1000Hz

For example I have signal like this:

Nx=64;
fs=1000;
t=1/fs*(0:Nx-1);

%==========================
A1=1;
A2=4;
f1=500;
f2=1000;

x1=A1*cos(2*pi*f1*t);
x2=A2*sin(2*pi*f2*t);
%==========================
x=x1+x2;
1
matlabsignal-processing
Is this homework? If so, please tag accordingly. – Thomas
And show us how far you have got. – High Performance Mark
Unfortunately, i do not know how to start. Ok, I use fft, but what and how should I do next? – Mateusz
For some reason, I missed this in matlab. Do you still need help with this HW? Just a quick note: the frequency of your second function, x2 is at the sampling frequency. As a result, it'll be incorrect (you'll only sample at the zeros of the sine). – abcd
Thanks, but I do not need help. :-) – Mateusz

1 Answers

1
votes

you are horrendously under-sampling your signal. You will be able to see your 500Hz sin wave, but just barely and your 1000Hz sine-wave wont appear where you would like it to. You will have aliasing issues.

You are also not going to see too many samples (64 samples is not enough data) MaxTime = 1;%second; fs = 2000; %minimum for shannon-nyquist t = 0:1/fs:MaxTime; %this ensures that you are getting the correct sampling rate and you can adjust the time range.

Noise Level = -infinity dB (there is no noise component here)