scipy.signal.lp2bp_zpk#
- scipy.signal.lp2bp_zpk(z, p, k, wo=1.0, bw=1.0)[source]#
Transform a lowpass filter prototype to a bandpass filter.
Return an analog band-pass filter with center frequency wo and bandwidth 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 passband center, as angular frequency (e.g., rad/s). Defaults to no change.
- bwfloat
Desired passband width, as angular frequency (e.g., rad/s). Defaults to 1.
- Returns:
- zndarray
Zeros of the transformed band-pass filter transfer function.
- pndarray
Poles of the transformed band-pass filter transfer function.
- kfloat
System gain of the transformed band-pass filter.
Notes
This is derived from the s-plane substitution
\[s \rightarrow \frac{s^2 + {\omega_0}^2}{s \cdot \mathrm{BW}}\]This is the “wideband” transformation, producing a passband with geometric (log frequency) symmetry about wo.
New in version 1.1.0.
Examples
Use the ‘zpk’ (Zero-Pole-Gain) representation of a lowpass filter to transform it to a bandpass filter with a center frequency wo and bandwidth bw.
>>> from scipy.signal import lp2bp_zpk >>> z = [ 5 + 2j , 5 - 2j ] >>> p = [ 7 , -16 ] >>> k = 0.8 >>> wo = 0.62 >>> bw = 15 >>> lp2bp_zpk(z, p, k, wo, bw) ( array([7.49955815e+01+3.00017676e+01j, 7.49955815e+01-3.00017676e+01j, 4.41850748e-03-1.76761126e-03j, 4.41850748e-03+1.76761126e-03j]), array([1.04996339e+02+0.j, -1.60167736e-03+0.j, 3.66108003e-03+0.j, -2.39998398e+02+0.j]), 0.8)