scipy.signal.lp2bs_zpk

scipy.signal.lp2bs_zpk(z, p, k, wo=1.0, bw=1.0)

Transform a lowpass filter prototype to a bandstop filter.

Return an analog band-stop filter with center frequency wo and stopband width bw from an analog low-pass filter prototype with unity cutoff frequency, using zeros, poles, and gain (‘zpk’) representation.

Parameters:

z : array_like

Zeros of the analog filter transfer function.

p : array_like

Poles of the analog filter transfer function.

k : float

System gain of the analog filter transfer function.

wo : float

Desired stopband center, as angular frequency (e.g. rad/s). Defaults to no change.

bw : float

Desired stopband width, as angular frequency (e.g. rad/s). Defaults to 1.

Returns:

z : ndarray

Zeros of the transformed band-stop filter transfer function.

p : ndarray

Poles of the transformed band-stop filter transfer function.

k : float

System gain of the transformed band-stop filter.

See also

lp2lp_zpk, lp2hp_zpk, lp2bp_zpk, bilinear, lp2bs

Notes

This is derived from the s-plane substitution

\[s \rightarrow \frac{s \cdot \mathrm{BW}}{s^2 + {\omega_0}^2}\]

This is the “wideband” transformation, producing a stopband with geometric (log frequency) symmetry about wo.

New in version 1.1.0.