Dear All, I just wonder if there is a simple way to calculate IFFT based on FFT results? Cheers, Yao
How to calculate IFFT based on FFT result?
Started by ●May 29, 2007
Reply by ●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 ●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 ●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 ●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 ●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 ●June 3, 20072007-06-03
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, > >YaoHello, 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 ●June 4, 20072007-06-04
On May 29, 4:41 am, Yao Sics <yao.s...@gmail.com> wrote:> I just wonder if there is a simple way to calculate IFFT based on FFT > results?Several common techniques are described at: http://en.wikipedia.org/wiki/Discrete_Fourier_transform#Expressing_the_inverse_DFT_in_terms_of_the_DFT
