Module « scipy.signal »

Fonction lp2bp - module scipy.signal

Signature de la fonction lp2bp

def lp2bp(b, a, wo=1.0, bw=1.0) 

Description

lp2bp.__doc__

    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, in transfer function ('ba') representation.

    Parameters
    ----------
    b : array_like
        Numerator polynomial coefficients.
    a : array_like
        Denominator polynomial coefficients.
    wo : float
        Desired passband center, as angular frequency (e.g., rad/s).
        Defaults to no change.
    bw : float
        Desired passband width, as angular frequency (e.g., rad/s).
        Defaults to 1.

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

    See Also
    --------
    lp2lp, lp2hp, lp2bs, bilinear
    lp2bp_zpk

    Notes
    -----
    This is derived from the s-plane substitution

    .. math:: 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`.

    Examples
    --------
    >>> from scipy import signal
    >>> import matplotlib.pyplot as plt

    >>> lp = signal.lti([1.0], [1.0, 1.0])
    >>> bp = signal.lti(*signal.lp2bp(lp.num, lp.den))
    >>> w, mag_lp, p_lp = lp.bode()
    >>> w, mag_bp, p_bp = bp.bode(w)

    >>> plt.plot(w, mag_lp, label='Lowpass')
    >>> plt.plot(w, mag_bp, label='Bandpass')
    >>> plt.semilogx()
    >>> plt.grid()
    >>> plt.xlabel('Frequency [rad/s]')
    >>> plt.ylabel('Magnitude [dB]')
    >>> plt.legend()