# scipy.signal.lp2bs_zpk¶

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

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. 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.

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.

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