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Given all the possible design options for IIR filters one could consider (e.g. Butterworth, Chebychev, inverse Chebychev, elliptic, Bessel, etc.) which design provides the least amount of phase shift in the pass band?

Here I'm assuming among the various designs considered, and for fair comparison that filter order and cutoff frequency are the same.

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  • \$\begingroup\$ It may be worth noting that in IIR digital filter design you are not limited to classical filter types (Buterworth, Chebyshev etc...). It is possible to design filters with arbitrary magnitude and phase. See uk.mathworks.com/help/dsp/examples/… \$\endgroup\$ – akellyirl Feb 18 '15 at 19:35
  • \$\begingroup\$ @akellyirl I'm more interested in the classical IIR filter designs. One can consider such zero phase filters (Matlab's filtfilt for example) but such a design requires backwards and forwards filtering- in other words it requires that all the data be acquired a-priori before the process of filtering can begin. The filter I'm looking for has to be causal,stable, realizable and be able to process signal in real time. Given all other things being equal, what filter gives the least phase delay? \$\endgroup\$ – docscience Feb 18 '15 at 20:38
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That sounds like the Bessel filter:

In electronics and signal processing, a Bessel filter is a type of analog linear filter with a maximally flat group/phase delay (maximally linear phase response), which preserves the wave shape of filtered signals in the passband. Bessel filters are often used in audio crossover systems.

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