code: def exponential_chirp(npts=2000):
      
      time = np.linspace(0, 20, npts)
      chirp = np.sin(2 * np.pi * 0.2 * (1.3 ** time - 1) / np.log(1.3))
      return chirp
docs: Generates an exponential chirp.
  
      :param npts: Number of samples.
      :type npts: int
      :returns: Generated signal
      :rtype: numpy.ndarray