Module « scipy.signal »

Fonction lp2bs - module scipy.signal

Signature de la fonction lp2bs

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

Description

lp2bs.__doc__

    Transform a lowpass filter prototype to a bandstop filter.

    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
        Numerator polynomial coefficients.
    a : array_like
        Denominator polynomial coefficients.
    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.

    See Also
    --------
    lp2lp, lp2hp, lp2bp, bilinear
    lp2bs_zpk

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

    .. math:: 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`.

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