SUFILTER - applies a zero-phase, sine-squared tapered filter

The program sufilter provides a general purpose zero-phase filtering capability for the usual tasks of bandpass, bandreject, lowpass, highpass, and notch filtering. Examples of each of these using sufilter data are provided

% suplane | sufilter f=10,20,30,60 amps=0,1,1,0 | suxwigb title="10,20,30,60 hz bandpass"  &

% suplane | sufilter f=10,20,30,60 amps=1,0,0,1 | suxwigb title="10,20,30,60 hz bandreject"  &

% suplane | sufilter f=10,20,30,60 amps=1,1,0,0 | suxwigb title="10,20 hz lowpass"  &

% suplane | sufilter f=50,60,70 amps=1,0,1 | suxwigb title="60 hz notch"  &

The filter is polygonal, with the corners of the polygon defined by the vector of frequency values defined by array of f= values, and a collection of amplitude values, defined by the array of amps= values. The amplitudes may be any floating point numbers greater than, or equal to zero. The only rule is that there must be the same number of amps values, as f values. The segments are sine-squared tapered between f values of different amplitude. It is best to select bf f values such that tapering to zero is done over an octave to prevent ringing.

With suplane, sufilter provides a way of easily generating bandlimited testpattern data in SU format.