`scipy.signal._filter_design:lp2bs`

source: build-install/usr/lib/python3.14/site-packages/scipy/signal/_filter_design.py:2253

Signature

def lp2bs(b, a, wo = 1.0, bw = 1.0)

Summary

Transform a lowpass filter prototype to a bandstop filter.

Extended Summary

Return an analog band-stop filter with center frequency wo and bandwidth bw from an analog low-pass filter prototype with unity cutoff frequency, in transfer function ('ba') representation.

Parameters

b : array_like, shape (M,): Numerator polynomial coefficients. Must be 1-D.
a : array_like, shape (N,): Denominator polynomial coefficients. Must be 1-D.
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

b : array_like: Numerator polynomial coefficients of the transformed band-stop filter.
a : array_like: Denominator polynomial coefficients of the transformed band-stop filter.

Notes

This is derived from the s-plane substitution

s \to \frac{s \cdot BW}{s ^{2} + ω _{0} ^{2}}

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

Examples

from scipy import signal
import matplotlib.pyplot as plt

✓

lp = signal.lti([1.0], [1.0, 1.5])
bs = signal.lti(*signal.lp2bs(lp.num, lp.den))
w, mag_lp, p_lp = lp.bode()
w, mag_bs, p_bs = bs.bode(w)

✓

plt.plot(w, mag_lp, label='Lowpass')
plt.plot(w, mag_bs, label='Bandstop')
plt.semilogx()

✗

[]

plt.grid(True)

✓

plt.xlabel('Frequency [rad/s]')
plt.ylabel('Amplitude [dB]')
plt.legend()

✗

<matplotlib.legend.Legend object at 0x7f3f68865d30>

Aliases

scipy.signal.lp2bs