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:
- zarray_like
Zeros of the analog filter transfer function.
- parray_like
Poles of the analog filter transfer function.
- kfloat
System gain of the analog filter transfer function.
- wofloat
Desired stopband center, as angular frequency (e.g., rad/s). Defaults to no change.
- bwfloat
Desired stopband width, as angular frequency (e.g., rad/s). Defaults to 1.
- Returns:
- zndarray
Zeros of the transformed band-stop filter transfer function.
- pndarray
Poles of the transformed band-stop filter transfer function.
- kfloat
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.
Added in version 1.1.0.
Examples
Transform a low-pass filter represented in ‘zpk’ (Zero-Pole-Gain) form into a bandstop filter represented in ‘zpk’ form, with a center frequency wo and bandwidth bw.
>>> from scipy.signal import lp2bs_zpk >>> z = [ ] >>> p = [ 0.7 , -1 ] >>> k = 9 >>> wo = 0.5 >>> bw = 10 >>> lp2bs_zpk(z, p, k, wo, bw) ( array([0.+0.5j, 0.+0.5j, 0.-0.5j, 0.-0.5j]), array([14.2681928 +0.j, -0.02506281+0.j, 0.01752149+0.j, -9.97493719+0.j]), -12.857142857142858)