Finite phase difference and Kay frequency estimation Estimates the instantaneous frequency of the input signal using General Phase Difference (FFD, CFD, 4th, 6th) and Kay Frequency Estimation Usage: ife = pde( signal, order [, window_length]); Inputs signal Input one dimensional signal to be analysed. order Order of the finite phase difference estimator. Available estimator orders are: 1, 2, 4, 6. window_length Kay smoothing window length in the case of weighted phase difference estimator. NB Set order = 1 for Kay's method. For General Phase Difference: window_length:0; order:1, 2, 4 or 6; e.g. ife = pde( signal, order); for Kay smoothing weighted phase difference: window_length: desired window length; order=1; e.g. ife = pde( signal, 0, window_length );