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# scipy.signal.besselap

`scipy.signal.``besselap`(N)

  Return (z,p,k) for analog prototype of an Nth order Bessel filter.

  The filter is normalized such that the filter asymptotes are the same as a Butterworth filter of the same order with an angular (e.g. rad/s) cutoff frequency of 1.

  Parameters: | N : int The order of the Bessel filter to return zeros, poles and gain for. Values in the range 0-25 are supported.
  Returns: | z : ndarray Zeros. Is always an empty array. p : ndarray Poles. k : scalar Gain. Always 1.