def exponential_chirp(npts=2000):
    """
    Generates an exponential chirp.

    :param npts: Number of samples.
    :type npts: int
    :returns: Generated signal
    :rtype: numpy.ndarray
    """
    time = np.linspace(0, 20, npts)
    chirp = np.sin(2 * np.pi * 0.2 * (1.3 ** time - 1) / np.log(1.3))
    return chirp
Generates an exponential chirp.

    :param npts: Number of samples.
    :type npts: int
    :returns: Generated signal
    :rtype: numpy.ndarray