Passive approximations of double‐exponent fractional‐order impedance functions

Abstract

SummaryDouble‐exponent fractional‐order impedance functions are important for modeling a wide range of biochemical materials and biological tissues. Through appropriate selection of the two exponents (fractional orders), the well‐known Havriliak–Negami, Cole–Cole, Cole–Davidson, and Debye relaxation models can be obtained as special cases. Here we show that an integer‐order Padé‐based approximation of the Havriliak–Negami function is possible to obtain and can be realized using appropriately configured Cauer/Foster resistor‐capacitor (RC) networks. Two application examples are subsequently examined: the emulation of the capacitive behavior in a polycrystalline solid electrolyte and the emulation of the impedance of four “fractal” vegetable types.