signal.py 文件源码

def freqz(b, a=1, fs=2.0, worN=None, whole=False):
    """Plot frequency response of a filter.

    This is a convenience function to plot frequency response, and internally uses
    :func:`scipy.signal.freqz` to estimate the response. For further details, see the
    documentation for :func:`scipy.signal.freqz`.

    :param b: numerator of a linear filter
    :param a: denominator of a linear filter
    :param fs: sampling rate in Hz (optional, normalized frequency if not specified)
    :param worN: see :func:`scipy.signal.freqz`
    :param whole: see :func:`scipy.signal.freqz`
    :returns: (frequency vector, frequency response vector)

    >>> import arlpy
    >>> arlpy.signal.freqz([1,1,1,1,1], fs=120000);
    >>> w, h = arlpy.signal.freqz([1,1,1,1,1], fs=120000)
    """
    import matplotlib.pyplot as plt
    w, h = _sig.freqz(b, a, worN, whole)
    f = w*fs/(2*_np.pi)
    fig = plt.figure()
    ax1 = fig.add_subplot(111)
    plt.plot(f, 20*_np.log10(abs(h)), 'b')
    plt.ylabel('Amplitude [dB]', color='b')
    plt.xlabel('Frequency [Hz]')
    plt.grid()
    ax1.twinx()
    angles = _np.unwrap(_np.angle(h))
    plt.plot(f, angles, 'g')
    plt.ylabel('Angle (radians)', color='g')
    plt.axis('tight')
    plt.show()
    return w, h