lp2lp — SciPy v1.15.3 Manual (original) (raw)

scipy.signal.

scipy.signal.lp2lp(b, a, wo=1.0)[source]#

Transform a lowpass filter prototype to a different frequency.

Return an analog low-pass filter with cutoff frequency _wo_from an analog low-pass filter prototype with unity cutoff frequency, in transfer function (‘ba’) representation.

Parameters:

barray_like

Numerator polynomial coefficients.

aarray_like

Denominator polynomial coefficients.

wofloat

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

Returns:

barray_like

Numerator polynomial coefficients of the transformed low-pass filter.

aarray_like

Denominator polynomial coefficients of the transformed low-pass filter.

Notes

This is derived from the s-plane substitution

\[s \rightarrow \frac{s}{\omega_0}\]

Examples

from scipy import signal import matplotlib.pyplot as plt

lp = signal.lti([1.0], [1.0, 1.0]) lp2 = signal.lti(*signal.lp2lp(lp.num, lp.den, 2)) w, mag_lp, p_lp = lp.bode() w, mag_lp2, p_lp2 = lp2.bode(w)

plt.plot(w, mag_lp, label='Lowpass') plt.plot(w, mag_lp2, label='Transformed Lowpass') plt.semilogx() plt.grid(True) plt.xlabel('Frequency [rad/s]') plt.ylabel('Amplitude [dB]') plt.legend()