Module « scipy.signal »

Fonction iirpeak - module scipy.signal

Signature de la fonction iirpeak

def iirpeak(w0, Q, fs=2.0) 

Description

iirpeak.__doc__

    Design second-order IIR peak (resonant) digital filter.

    A peak filter is a band-pass filter with a narrow bandwidth
    (high quality factor). It rejects components outside a narrow
    frequency band.

    Parameters
    ----------
    w0 : float
        Frequency to be retained in a signal. If `fs` is specified, this is in
        the same units as `fs`. By default, it is a normalized scalar that must
        satisfy  ``0 < w0 < 1``, with ``w0 = 1`` corresponding to half of the
        sampling frequency.
    Q : float
        Quality factor. Dimensionless parameter that characterizes
        peak filter -3 dB bandwidth ``bw`` relative to its center
        frequency, ``Q = w0/bw``.
    fs : float, optional
        The sampling frequency of the digital system.

        .. versionadded:: 1.2.0

    Returns
    -------
    b, a : ndarray, ndarray
        Numerator (``b``) and denominator (``a``) polynomials
        of the IIR filter.

    See Also
    --------
    iirnotch

    Notes
    -----
    .. versionadded:: 0.19.0

    References
    ----------
    .. [1] Sophocles J. Orfanidis, "Introduction To Signal Processing",
           Prentice-Hall, 1996

    Examples
    --------
    Design and plot filter to remove the frequencies other than the 300 Hz
    component from a signal sampled at 1000 Hz, using a quality factor Q = 30

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

    >>> fs = 1000.0  # Sample frequency (Hz)
    >>> f0 = 300.0  # Frequency to be retained (Hz)
    >>> Q = 30.0  # Quality factor
    >>> # Design peak filter
    >>> b, a = signal.iirpeak(f0, Q, fs)

    >>> # Frequency response
    >>> freq, h = signal.freqz(b, a, fs=fs)
    >>> # Plot
    >>> fig, ax = plt.subplots(2, 1, figsize=(8, 6))
    >>> ax[0].plot(freq, 20*np.log10(np.maximum(abs(h), 1e-5)), color='blue')
    >>> ax[0].set_title("Frequency Response")
    >>> ax[0].set_ylabel("Amplitude (dB)", color='blue')
    >>> ax[0].set_xlim([0, 500])
    >>> ax[0].set_ylim([-50, 10])
    >>> ax[0].grid()
    >>> ax[1].plot(freq, np.unwrap(np.angle(h))*180/np.pi, color='green')
    >>> ax[1].set_ylabel("Angle (degrees)", color='green')
    >>> ax[1].set_xlabel("Frequency (Hz)")
    >>> ax[1].set_xlim([0, 500])
    >>> ax[1].set_yticks([-90, -60, -30, 0, 30, 60, 90])
    >>> ax[1].set_ylim([-90, 90])
    >>> ax[1].grid()
    >>> plt.show()