I am imposing a signal such as 60cos(21t) + 40cos(42t) + 20cos(63t). So I am supposed to get the following amplitude and frequency from the FFT signal.
1) Frequency (21), Amplitude (60)
2) Frequency (42), Amplitude (40)
3) Frequency (63), Amplitude (20).
The following script used to obtain the above FFT results:
Start_time = 0;
End_time = 10;
range = End_time-Start_time;
FFT_zone = 1/range;
NPL = ((range)/dt)+1;
IS = (Start_time/dt)+1;
Ns = IS+NPL-1;
Ns1 = (((range)/dt)-150);
columns = 2;
eval(['Vector_selected1=Rin.signal(:,' num2str(i) ');']);
eval(['Vector_selected2=Vector_selected1(' num2str(IS) ':' num2str(Ns) ');']);
[r,c] = size(Rin.Frequency_vector);
Rin.xx11(1,1) = 0;
The following signals are obtained by using the macro.
SIGNAL 1 SIGNAL 2
In the first signal, i am getting the FFT amplitude are almost closer to my expectation. But in the second signal, the FFT amplitudes are deviates from my expectation. In Inputs, The only deviation between both signals are start time and end time.
For signal 1 --> Start time = 0, End time = 10
For signal 2 --> Start time = 4, End time = 6.
Total available signal time = 10 s.
Eventhough both siganl are same, due to the zoomed windowing time leads to the deviation in FFT amplitudes. So i need to avoid this issue.
Kindly help me out on this.
Thanks in advance.