Re: can we just see the Fourier Spectrum of a filter and know if it is a FIR or a IIR?

"VijaKhara" <VijaKhara@xxxxxxxxx> wrote in message
news:1142959978.601223.284610@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I have a unit response function h(n), and its DFT is H(n). I am
wondering if we just see the H(n) and know if it is a FIR or a IIR? I
think we cannot since just look at the H(n) I cannot see any noticeable
difference.

Thanks

I'd say you are correct - in general.
BTW - I presume you mean H(f) (not H(n))
H(f) can have a magnitude vs freq and a phase vs freq. You might be able to
guess a little better if you looked at the phase vs freq response. A
non-linear phase response makes it likely that your filter is a non-FIR
filter.

A few more notes on terminology. I could have an impulse response h(n) which
describes the transfer function of a black box (say a room). I could choose
to use an FIR or IIR implementation that approximates this impulse response
h(n) (call it h(n)'). Studying h(n) and its DFT will give you close to
nothing. Studying h(n)' and its DFT might give a few clues on the filter
(which we've already talked about).

Cheers
Bhaskar


.

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