Since it represents the spectrum by an all-pole model, the correct choice of the model order p is crucial. Fs specifies the signal's sampling frequency, which is used to scale the output frequency vector freq . If the input signal is complex, freq ranges from 0 to Fs . Fs defaults to 2 if not specified. In this case, the model order must be four or larger, because each real sinusoid is the sum of two complex exponentials.
Experience shows that taking a larger model order than the minimum seems to work better.
See Also lpc Linear prediction coefficients.