A note on applications of time-domain solution of Cole permittivity models

The complex dielectric permittivity is an important parameter for characterization of electrical properties of dielectric materials. Experimental studies demonstrated that Cole models of dielectric permittivity can provide a better fitting to the experimental data because of allowing for fractional-order frequency dependence. This study aims to investigate physical interpretation of time domain solutions of Cole permittivity models. For this purpose, impulse responses of Cole-Cole model and Davidson-Cole model are expressed in Mittag-Leffler function form by using inverse Laplace transform. The impulse responses of these models are decomposed into impulsive and dispersive components, and the relations of these components with relaxation mechanism of dielectric materials are discussed. By considering impulse response solution of Cole-Cole models, a fractional order dynamic capacitance model is introduced for time domain equivalent circuit modeling of dielectric materials. Moreover, transient properties of electromagnetic wave penetration to dielectric materials are analyzed according to impulse response solution of Cole-Cole model. To illustrate applications of proposed time domain permittivity solutions, the Cole-Cole model of ethyl-acetate liquids was also studied and results are presented.