How to derive the time axis for the ifft of an oscillating pulse?
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Hello, I have an oscillating pulse in the frequency domain that I would like to ifft and find the time signal. My signal looks like:
![PulseFrequencyPicture.jpg](https://www.mathworks.com/matlabcentral/answers/uploaded_files/260662/PulseFrequencyPicture.jpeg)
And comes from the following code:
sampleRate = 1000;
freq = 500 : (1/sampleRate) : 1500;
intensityFreq = exp(-((freq-1000).^2));
signalFreq = sqrt(intensityFreq).*exp(-1i*10*(freq-1000));
plot(freq,signalFreq)
When I ifft, it doens't automatically produce the time axis, and also shows a similar oscillating pulse (in time) whose oscillations depends on the frequency range I used in the above code. For example, when:
freq = 500 : (1/sampleRate) : 1500;
is used (as in the code shown above), the ifft looks like:
![PulseTimePictureHigh.jpg](https://www.mathworks.com/matlabcentral/answers/uploaded_files/260663/PulseTimePictureHigh.jpeg)
While when:
freq = 980 : (1/sampleRate) : 1020;
Is used instead, the ifft looks like:
![PulseTimePictureLow.jpg](https://www.mathworks.com/matlabcentral/answers/uploaded_files/260664/PulseTimePictureLow.jpeg)
This makes no sense to me, since the frequency range shouldn't matter since signalFreq goes to 0 around these points anyway. Why does the altered frequency range affect the oscillations in the ifft so much? And how do I obtain the valid time axis for my output?
Any help is appreciated. If my explanation isn't clear I'll be happy to provide more detail.
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