How can I increase the number of samples in my original time domain signal when doing iFFT?

How can I increase the number of samples in my original time domain signal when doing iFFT?

I have a sampled time domain signal composed of a number of sinusoids. I have around 1700 samples, I've done an FFT to see the spectrum and I'd like to use iFFT to extend it past my last sample of the time domain signal. i.e. I have 1700 samples and I like to see what the time domain signal looks like between 1700 - 2500 samples.

How can I increase the iFFT samples to look foward in time to see from 1700 - 2500 samples in the time domain signal?

Each of the sinusoids has a different phase, so I can't just reconstruct it just from the spectrum using each frequency starting at zero radians. I've tried to do this with just scripts. However, I also have the signal processing toolbox, but I can't figure out if the signal processing toolbox package can help me to do this, or whether I need to do this using scripts.

Is there a way to do this in the signal processing toolbox package and/or can I do this using scripts?

Answer 1

[Gokul Nath S J]

Hi Sandy Messini,

As per my understanding, you might need to take N (2500) point Inverse fast Fourier Transform (ifft) of a signal containing n (1700) samples where N > n. The following code will compute N (N > n) point ifft of a sequence ‘signal’.

ifft(signal, N);

Refer to the attached documentation for more info.

https://in.mathworks.com/help/matlab/ref/ifft.html