From: alex65111 on
Let's assume at us is available 1024 discrete samples. Further it is
carried out FFT. Whether probably from received 1024 spectral samples to
receive 256 spectral samples which are equivalent as if we have executed
FFT only on 256 input discrete samples?
From: Jerry Avins on
On 5/19/2010 2:39 PM, alex65111 wrote:
> Let's assume at us is available 1024 discrete samples. Further it is
> carried out FFT. Whether probably from received 1024 spectral samples to
> receive 256 spectral samples which are equivalent as if we have executed
> FFT only on 256 input discrete samples?

I'm sorry. I can decode the first two sentences, but not the last one. I
simply can't imagine what you are trying to ask.

Jerry
--
"I view the progress of science as ... the slow erosion of the tendency
to dichotomize." --Barbara Smuts, U. Mich.
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From: alex65111 on
>On 5/19/2010 2:39 PM, alex65111 wrote:
>> Let's assume at us is available 1024 discrete samples. Further it is
>> carried out FFT. Whether probably from received 1024 spectral samples
to
>> receive 256 spectral samples which are equivalent as if we have
executed
>> FFT only on 256 input discrete samples?
>
>I'm sorry. I can decode the first two sentences, but not the last one. I
>simply can't imagine what you are trying to ask.
>
>Jerry
>--
>"I view the progress of science as ... the slow erosion of the tendency
> to dichotomize." --Barbara Smuts, U. Mich.
>???????????????????????????????????????????????????????????????????????
>


Let's assume there are 1024 samples X = [X1...X1024].
Y=FFT(X), Y =[Y1...Y1024].
It is required from Y to receive Z, where Z=FFT(X1...X256)
or
Z=FFT((X1...X256 + X257...X512 + X513...X768 + X769...X1024)/4).
From: Jerry Avins on
On 5/19/2010 3:42 PM, alex65111 wrote:
>> On 5/19/2010 2:39 PM, alex65111 wrote:
>>> Let's assume at us is available 1024 discrete samples. Further it is
>>> carried out FFT. Whether probably from received 1024 spectral samples
> to
>>> receive 256 spectral samples which are equivalent as if we have
> executed
>>> FFT only on 256 input discrete samples?
>>
>> I'm sorry. I can decode the first two sentences, but not the last one. I
>> simply can't imagine what you are trying to ask.
>>
>> Jerry
>> --
>> "I view the progress of science as ... the slow erosion of the tendency
>> to dichotomize." --Barbara Smuts, U. Mich.
>> ???????????????????????????????????????????????????????????????????????
>>
>
>
> Let's assume there are 1024 samples X = [X1...X1024].
> Y=FFT(X), Y =[Y1...Y1024].
> It is required from Y to receive Z, where Z=FFT(X1...X256)
> or
> Z=FFT((X1...X256 + X257...X512 + X513...X768 + X769...X1024)/4).

Reconstitute the original samples with IFFT(Y) and go from there.

Jerry
--
"I view the progress of science as ... the slow erosion of the tendency
to dichotomize." --Barbara Smuts, U. Mich.
�����������������������������������������������������������������������
From: alex65111 on
>Reconstitute the original samples with IFFT(Y) and go from there.
>
>Jerry
>--
>"I view the progress of science as ... the slow erosion of the tendency
> to dichotomize." --Barbara Smuts, U. Mich.
>???????????????????????????????????????????????????????????????????????
>

The problem to receive result without reconstruction, operating only with
spectral samples.