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From: clayss on 21 Jan 2010 08:15
How does an FIR asymmetric bandpass filter perform differently than a
symmetric bandpass filter with the same magnitude and phase response at
positive frequencies?


From: Rune Allnor on 21 Jan 2010 08:21
On 21 Jan, 14:15, "clayss" <cshe...(a)gmail.com> wrote:
> How does an FIR asymmetric bandpass filter perform differently than a
> symmetric bandpass filter with the same magnitude and phase response at
> positive frequencies?  

Depends on what kind of asymmetry you mean:

Time-domain symmetry means that the frequency response has
linear phase. So a FIR that is asymmetric in time domain
will have non-linear phase in frequency domain.

Conjugate symmetry in frequency domain means the time-domain
impulse response is real-valued. If the frequency response
is not conjugate symmetric, the time-domain impulse response
becomes complex-valued.

Rune
From: Clay on 21 Jan 2010 16:02
On Jan 21, 8:15 am, "clayss" <cshe...(a)gmail.com> wrote:
> How does an FIR asymmetric bandpass filter perform differently than a
> symmetric bandpass filter with the same magnitude and phase response at
> positive frequencies?  

You have a contradictory requirement in your question. An asymmtric
FIR filter is easily decomposed into the sum of a symmetric and an
antisymmtric FIR filter. The antisymmtric part has a 90 degree phase
shift. So if your filter is asymmetric how can it both simultaneously
match the magnitude and phase response of a symmetric FIR filter even
if just looking at positive frequencies. The symmetric FIR filter's
phase repsonse is a zero degree phase shift apart from the overall
delay required for causality.

IHTH,

Clay
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