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DFT without the DC component

Started by m26k9 ●May 26, 2009
Reply by dbd ●May 27, 20092009-05-27
On May 26, 7:06 pm, "m26k9" <maduranga.liyan...@gmail.com> wrote:

> >If there is no leakage, then the samples you have are completely
> >independent of the DC sample, so the DC sample cannot be calculated in
> >any manner from the samples you have.
>
> >It's time to find a basis for leakage or give up.
>
> >Dale B. Dalrymple
>
> Thank you Dale.
> It seems so that I cannot go from here. Only option I have left right now
> is the averging and see if it can give a close enough answer for the
> parameters I am working with, or use the inverse of the DFT matrix minus
> the first row and last column. But a matrix inverse is not a very welcome
> calculation :-(


It is your statement that there is no leakage that promises that the
results of any averaging or matrix inversion will be independent of
the value of the DC component.

Dale B. Dalrymple
Reply by Jerry Avins ●May 27, 20092009-05-27
m26k9 wrote:

>> Do you in fact have the original samples to average over?
>>
>> Jerry
> 
> Yes I do have the original samples. This is a simulation so I have the
> samples. But receiver has no knowledge of them. So I cannot use them to
> calculate the DC.


The receiver can never see or be affected by the DC. If you think you 
need it to understand what the receiver does, there's a flaw in the 
simulation.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
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Reply by Jerry Avins ●May 27, 20092009-05-27
m26k9 wrote:

>> What is the significance of the DC value to a channel that cannot 
>> support DC?
>>
>> Jerry
> 
> I think I may have quoted my question in an ambiguous way. What I meant by
> DC value is the value H(0) of the Fourier transform of my channel h(n). I
> am trying to estimate h(n) from H(f), but I cannot calculate the H(0),
> while H(1) to H(N-1) are known. This is what I meant by no DC. I need to
> find H(0) so that I can IDFT them to find h(n).


If there's no H(0), there's no DC. The theory really works!

Jerry
-- 
Engineering is the art of making what you want from things you can get.
&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;
Reply by m26k9 ●May 28, 20092009-05-28
>If there's no H(0), there's no DC. The theory really works!


Actually there is a H(0). My calculations only let me find from H(1) to
H(N-1). So I have to find H(0) from some other method (like finding the
average of the channel impulses) so I can construct the complete sequence
H(0) to H(N-1) and do IDFT to find the channel impulse response h(n). 

Thank you very much for all the help guys.