comp.lang.idl-pvwave archive: archive

Home » Public Forums » archive » Inverse FFT

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Inverse FFT [message #33281 is a reply to message #33221]

Tue, 17 December 2002 06:42

R.G. Stockwell
Messages: 363
Registered: July 1999

Senior Member

Colin Ault wrote:

> Hi,
>
> Thanks for the comments and suggestions.
>
> I am packing the negative frequencies correctly (I hope!) - just using
> the same method in the online FFT example. I call this array k_points,
> and this ranges thus 0, 0.01, 0.02.....,0.50, -0.49, ...., -0.02,
> -0.01. This is for 100 points sampled at T=1.0 seconds.
>
> I then compute the FFT via the normal method, FFT(function), and
> obtain my expected spectral pattern. So far, so good!
>
> I then use the following code to compute (manually) the inverse:
>
> FOR j=0, n-1 DO BEGIN
>
> spec_sig = FT*exp(2*pi*k_points * t[j]/n)
>
> new_signal[j] = TOTAL(spec_sig)
>
> ENDFOR
>
> FT is an array holding the fourier transform of my function

Perhaps it was a typo, but don't you want

spec_sig = FT*exp(complex(0,1)*2*!pi*k_points * t[j]/n)

(And make sure FT is complex)

Cheers,
bob stockwell

Report message to a moderator

[Message index]

		Inverse FFT By: aultc on Mon, 16 December 2002 08:33
		Re: Inverse FFT By: R.G. Stockwell on Tue, 17 December 2002 07:02
		Re: Inverse FFT By: aultc on Wed, 18 December 2002 01:19
		Re: Inverse FFT By: R.G. Stockwell on Tue, 17 December 2002 06:42
		Re: Inverse FFT By: aultc on Tue, 17 December 2002 03:10
		Re: Inverse FFT By: aultc on Tue, 17 December 2002 03:06
		Re: Inverse FFT By: jeyadev on Mon, 16 December 2002 15:56
		Re: Inverse FFT By: Streun Andreas on Mon, 16 December 2002 10:01
		Re: Inverse FFT By: R.G. Stockwell on Mon, 16 December 2002 09:53

Previous Topic:	What I Want for Christmas.
Next Topic:	Re: IDLDE refresh in Windows XP (IDL 5.2.1)

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Thu Oct 09 20:24:55 PDT 2025

Total time taken to generate the page: 0.00607 seconds