
DFP2 Option
923134 Rev A ISSUED: June 2013 9
IIR Filters
Infinite Impulse Response (IIR) filters are digital filters that emulate analog filters. The four types
offered by the DFP2 option are as follows:
• Butterworth
• Chebyshev
• Inverse Chebyshev
• Bessel
The Butterworth or "maximally flat" filter has the flattest amplitude response of all the available
filters. The Bessel filter is noted for its uniform phase response as a function of frequency. The
following figure shows a comparison between Butterworth and Bessel filters. Note that the Bessel
filter has a wider transition bandwidth, but linear phase within the pass band.
If you need the fastest rollo
ff, the Chebyshev filters have the narrowest transition region for a
given number of stages. However, the Chebyshev filter has ripple in the pass band, while the
Inverse Chebyshev filter exhibits a flat pass band response, but has ripple in the stop band.
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