 ### Jon Leman (@jleman)

Power systems engineer. 18 years in consulting. Currently pursuing PhD.

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

Thanks for taking the time to type this up, twice apparently.  Much appreciated.  The examples help a lot.  I'll be working through this today.

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

Thank you.  That is very helpful.  I will review this information in more detail next week, but two questions come to mind:  1) speed is important in my code...

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

Negative - power systems.. as in high voltage transmission line electromagnetics.  I don't work in controls, but am aware that much DSP is involved in that area...

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

And thanks to other folks who posted - those conversations helped get me oriented.

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

Excellent!  Thanks for the help.  I'm in power systems and never expected to delve into the DSP realm. However, it has been very interesting.  It seems the...

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

Ok. That makes sense and I was able to get things to work.  I had to experiment a bit and I'm not sure I quite matched your description above, but the attached...

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

Do you mean:  ...You should be able to map the DFT bins 0 to N/2 on your domain of 0 to 3, then N/2 to N on your domain of -3 to 0...?

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

I reviewed your answers in the other forums and I think they do relate to the specific concepts I am confused about.  Taking a step back, attached is a better...

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

Thanks.  I think I see what you are getting at. A lot of good responses on this forum. I need to let all this information simmer and sink in.

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

Fair enough.  Poorly worded on my part.  Plot A is spectrum plot.  Thanks for the link.  I will review.  It looks helpul at first glance.

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

Adding to this - the integration method is quite slow which is why I'm trying to do this by discrete methods.  When it is all said an done I would like to understand...

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

I can get this as well, but this is the result obtained using the typical transform pair involving exp(i*2*pi*gamma*t).  Also, the imaginary component of the...

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

I obtained B by inverse Fourier transform of A.  My code implements what I'm calling the continuous form because it integrates the original continuous frequency...

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

Post above in a reply to Platybek...signals.xlsx

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

The problem is related to electric field analysis. I have confirmed through independent means that figure B is correct from a spatial point of view. The calculus...

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

Comments:OK, so you started with curves A and by algebra and calculus you computed curves B which are the time response (you call it a spatial response, makes no...

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

This is the data for all four plots.  Plots without data for the horizontal axes are just indexed based on array position.  Thanks for the help.signals.xlsx

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

The attached pdf has supplementary info.  I try a different way of asking the question and I include some code snippets with examples of their function calls. ...

## Re: Inverse DFT of frequency domain signal sampled from a continuous function

Thank you for the reply.  The code is written in Julia and all numbers are complex, though as you say, the imaginary part in the spatial domain is zero (or very-very...

## Inverse DFT of frequency domain signal sampled from a continuous function

I have a continuous function that defines a 1D frequency domain signal.  Plot A in the attached image shows the real and imaginary portions of the sampled signal...

## Re: Inverse FFT of a Sampled Frequency Domain Function

My data is in Cartesian so it sounds like I need to create a complex conjugate array, reverse the order and prepend to the existing array.  Thanks!

## Re: Inverse FFT of a Sampled Frequency Domain Function

Thanks!  If I proceed to process the input array directly, am I correct in my understanding that only the first half of the resulting time array is "useful"?

## Inverse FFT of a Sampled Frequency Domain Function

Pardon the basic nature of this question.  DSP is not my area of expertise.  I have an equation for a continuous frequency domain function - I'll call it Z(jω)...

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