LinearSystems.LowpassToBandpass Method (TVec, TVec, TSample, TSample, TSample)

Frequency transformation from a lowpass to a bandpass filter in s-domain.

public LowpassToBandpass(TVec z, TVec p, ref double k, double CenterFreq, double Bw);

Remarks

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

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

  Wl - lower cutoff frequency
  Wu - upper cutoff frequency

The routine also adds zeros at 0. It adds one zero, if the lowpass filter order is odd and already has zeros. If the filter does not have zeros, it adds sufficient zeros at 0 to match the order of the lowpass filter.

References:

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