On Sep 22, 8:22=A0am, Dave <dspg...@netscape.net> wrote:
> On Sep 21, 1:13=A0pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
>
>
>
>
>
> > mackenfy wrote:
>
> > >>mackenfy wrote:
>
> > >>>what is IFFT (inverse FFT) equation. And how to derive it from FFT
> > >>>equation?
> > >>>=3D20
> > >>>Is FFT equation same as DFT equation which is X(k)=3D3D =3DCE=3DA3
> > >>>x(n)e^(-j*2*pi*k*n/N)
> > >>>=3DCE=3DA3 is from k=3D3D0 to N-1
> > >>>????
> > >>>=3D20
> > >>>and what is equation for IDFT and IFFT?
>
> > > What???????
>
> > > And what is STUPIDENT????? you?
>
> > > if you don't help don't reply!
>
> The Fast Fourier Transform (FFT) is merely a fast way of calculating
> the DFT (Discrete Fourier Transform).
Provided the sampling is uniform.
Hope this helps.
Greg
Reply by Dave●September 22, 20112011-09-22
On Sep 21, 1:13�pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
> mackenfy wrote:
>
> >>mackenfy wrote:
>
> >>>what is IFFT (inverse FFT) equation. And how to derive it from FFT
> >>>equation?
> >>>=20
> >>>Is FFT equation same as DFT equation which is X(k)=3D =CE=A3
> >>>x(n)e^(-j*2*pi*k*n/N)
> >>>=CE=A3 is from k=3D0 to N-1
> >>>????
> >>>=20
> >>>and what is equation for IDFT and IFFT?
>
> > What???????
>
> > And what is STUPIDENT????? you?
>
> > if you don't help don't reply!
The Fast Fourier Transform (FFT) is merely a fast way of calculating
the DFT (Discrete Fourier Transform).
Given your original equation you want to solve for x(n). You can do
this by using the orthogonal properties of the discrete exponential.
Multiply both sides by an exponential and carry out a summation. Do to
the orthogonality some of the summations in the starting equation
will disappear.
Cheers,
David
Reply by Vladimir Vassilevsky●September 21, 20112011-09-21
mackenfy wrote:
>>
>>mackenfy wrote:
>>
>>
>>>what is IFFT (inverse FFT) equation. And how to derive it from FFT
>>>equation?
>>>=20
>>>Is FFT equation same as DFT equation which is X(k)=3D =CE=A3
>>>x(n)e^(-j*2*pi*k*n/N)
>>>=CE=A3 is from k=3D0 to N-1
>>>????
>>>=20
>>>and what is equation for IDFT and IFFT?
>>
>
> What???????
>
> And what is STUPIDENT????? you?
>
> if you don't help don't reply!
Reply by mackenfy●September 21, 20112011-09-21
>
>
>mackenfy wrote:
>
>> what is IFFT (inverse FFT) equation. And how to derive it from FFT
>> equation?
>>=20
>> Is FFT equation same as DFT equation which is X(k)=3D =CE=A3
>> x(n)e^(-j*2*pi*k*n/N)
>> =CE=A3 is from k=3D0 to N-1
>> ????
>>=20
>> and what is equation for IDFT and IFFT?
>
What???????
And what is STUPIDENT????? you?
if you don't help don't reply!
Reply by Tauno Voipio●September 21, 20112011-09-21
On 21.9.11 7:52 , mackenfy wrote:
> what is IFFT (inverse FFT) equation. And how to derive it from FFT
> equation?
>
> Is FFT equation same as DFT equation which is X(k)= Σ
> x(n)e^(-j*2*pi*k*n/N)
> Σ is from k=0 to N-1
> ????
>
> and what is equation for IDFT and IFFT?
It seems that you need some basics: Google for
'Fourier series' and 'Fourier transform'.
FFT is an efficient way of computing the
discrete Fourier transform. The basic
mathematics stay the same.
--
Tauno Voipio
Reply by Vladimir Vassilevsky●September 21, 20112011-09-21
mackenfy wrote:
> what is IFFT (inverse FFT) equation. And how to derive it from FFT
> equation?
>=20
> Is FFT equation same as DFT equation which is X(k)=3D =CE=A3
> x(n)e^(-j*2*pi*k*n/N)
> =CE=A3 is from k=3D0 to N-1
> ????
>=20
> and what is equation for IDFT and IFFT?
Reply by mackenfy●September 21, 20112011-09-21
what is IFFT (inverse FFT) equation. And how to derive it from FFT
equation?
Is FFT equation same as DFT equation which is X(k)= Σ
x(n)e^(-j*2*pi*k*n/N)
Σ is from k=0 to N-1
????
and what is equation for IDFT and IFFT?