LinearSystems

Transform a lowpass filter prototype in zero-pole form to a bandstop filter, where the stopband has width BW centered around the frequency CenterFreq. Assumed sampling frequency is 2. The transformation is defined as ([1], p. 258):

          s(Wu - Wl)
  s --> -------------
         s^2 + Wu*Wl

  Wl - lower cutoff frequency
  Wu - upper cutoff frequency

The routine also adds pairs of zeros at +/-j*CenterFreq, if the number of zeros is less then number of poles, to match the number of poles. 

References:  

[1] Theory and application of digital signal processing, Lawrence R. Rabiner and Bernard Gold. Prentice-Hall, 1975

Functions