On 29 May 2007 01:41:23 -0700, Yao Sics <yao.sics@gmail.com> wrote:
>Dear All,
>
>I just wonder if there is a simple way to calculate IFFT based on FFT
>results?
>
>Cheers,
>
>Yao
Hello,
If you question is:
How do I compute the IFFT using a (forward)
FFT algorithm?"
One answer is:
(1) Conjugate your freq-domain samples,
(2) Perform a forward FFT on the conjugated
samples,
(3) Conjugate the foward FFT result samples,
(4) Divide your final results by N (N is the
FFT size).
[-Rick-]
Reply by Jerry Avins●May 29, 20072007-05-29
Chris Barrett wrote:
> Yao Sics wrote:
>> Dear All,
>>
>> I just wonder if there is a simple way to calculate IFFT based on FFT
>> results?
>>
>> Cheers,
>>
>> Yao
>>
>
> IFFT is the same thing as the FFT of the complex conjugate.
Depending on the implementation, there may be a scaling issue.
Please ignore my silly answer of a few minutes ago. I misunderstood the
question.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply by Jerry Avins●May 29, 20072007-05-29
Yao Sics wrote:
> Dear All,
>
> I just wonder if there is a simple way to calculate IFFT based on FFT
> results?
FFT<-->IFFT is a transform pair. If you know one, you can compute the
other. If you know both, there's no need to compute either. If you still
have the original data, use it. Otherwise, you start from scratch. What
was the question?
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply by Chris Barrett●May 29, 20072007-05-29
Yao Sics wrote:
> Dear All,
>
> I just wonder if there is a simple way to calculate IFFT based on FFT
> results?
>
> Cheers,
>
> Yao
>
IFFT is the same thing as the FFT of the complex conjugate.
Reply by Yao Sics●May 29, 20072007-05-29
On May 29, 6:22 pm, Sastry <sastry.vadlam...@gmail.com> wrote:
> On May 29, 1:41 pm, Yao Sics <yao.s...@gmail.com> wrote:
>
> > Dear All,
>
> > I just wonder if there is a simple way to calculate IFFT based on FFT
> > results?
>
> > Cheers,
>
> > Yao
>
> "Numerical Recipes in C" explains some algorithms there. Hope that
> will help.
Thanks, Sastry.
I just found there is a very simple method to compute IFFT by using
the result of FFT.
To compute IFFT, first interchange real and imag parts, then perform
FFT, and, finally interchange the real and imag parts, divide by N. I
compared the result with matlab built-in ifft. The result is correct!
Hope this would help someone looking for the similar question
Yao
Reply by Sastry●May 29, 20072007-05-29
On May 29, 1:41 pm, Yao Sics <yao.s...@gmail.com> wrote:
> Dear All,
>
> I just wonder if there is a simple way to calculate IFFT based on FFT
> results?
>
> Cheers,
>
> Yao
"Numerical Recipes in C" explains some algorithms there. Hope that
will help.
Reply by Yao Sics●May 29, 20072007-05-29
Dear All,
I just wonder if there is a simple way to calculate IFFT based on FFT
results?
Cheers,
Yao