Algorithm 1 Signal Period Extraction.

Input: Measured signal x

Period search range [T1, T2]

Maximum number of iterations k

Threshold valued thre = 0

Output: Signal period T

Initialize the input parameters;

for i = 1 to k

xxi = ACF(x)         Compute the ACF of x, Equation (8)

indi = AKE(xxi(T1:T2))    Compute the AKE of ACF, Equation (12)

x = xxi

if i > 1

if indi > thre

j = i          Obtain the optimal number of iterations

thre = indi

end if

end if

end

[~, T] = max(xxj( T1:T2))       Identify the signal period T