A rational discrete approximation to the operator s/sup 0.5

This letter deals with the discrete approximation of the fractional-order differentiator s/sup 0.5/. The proposed approach is based on the efficient continued fraction approximation of the operator. The discrete differentiator is expressed as a z-transfer function, whose coefficients are given in closed form in terms of the sampling time and an approximation parameter. Simulation experiments show the efficiency of the approximation with low-order z-transfer functions.