An improved model for the resonant frequency of tunable rectangular microstrip antenna

An improved model for the resonant frequency of a tunable rectangular microstrip antenna is presented. The influence of fringing fields and air gap between the dielectric substrate and ground plate on the resonant frequency is taken into consideration by introducing effective width W_eff and effective length L_eff, equivalent permittivity ε_r,equ and dynamic permittivity ε_r,dyn. The theoretic values are compared with experimental values, showing good agreement.