Teledyne LeCroy DFP2 - Digital Filter Package 2 - Manual (Page 11)

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 rolloff, 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.