2nd vs 1st order all pass filter
Started by ●May 27, 2013
Given that the magnitude response of a first order all pass filter is perfectly
flat, what reasons are there to consider a filter greater than one order?
Presumably it is to do with varying the phase in a different way, but can anyone
give me a good real world application?
Reply by ●May 27, 20132013-05-27
With an analog implementation, there is a trade-off between
the amount of group delay you can get and the frequency range over which the
group delay will be relatively constant. Higher order all-pass filters will provide a constant specified group delay over
a wider range of frequencies. Of course,
with a digital implementation you can theoretically get a constant delay over
an infinite range of frequencies. See
the following:
T Kugelstadt “Active
Filter Design Techniques” http://www.ti.com/lit/ml/sloa088/sloa088.pdf
Douglas Self “The
Design of Active Crossovers” Chapter 10 (Not Available online.)
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the amount of group delay you can get and the frequency range over which the
group delay will be relatively constant. Higher order all-pass filters will provide a constant specified group delay over
a wider range of frequencies. Of course,
with a digital implementation you can theoretically get a constant delay over
an infinite range of frequencies. See
the following:
T Kugelstadt “Active
Filter Design Techniques” http://www.ti.com/lit/ml/sloa088/sloa088.pdf
Douglas Self “The
Design of Active Crossovers” Chapter 10 (Not Available online.)
_____________________________________
