Determination of Effective Dielectric Constant and Resonant Frequency of Microstrip Patch Antenna with Multilayered Superstrate Structures

A generic iterative empirical model to compute the effective permittivity (ε_eff) and resonant frequency (f_r) of microstrip patch antenna (MPA) covered with multi-layered superstrates is reported. For an MPA covered with multi-layers of superstrate the presented technique makes use of conformal mapping (CM) of dielectric boundaries and series-parallel combination of capacitances between the metallic patch and ground plane to determine ε_eff. The developed model can accurately predict ε_eff and f_r of multi-layered superstrate structure with permittivity greater than 4.5 which is higher than the previous state-of-the-art (i.e. ε_r>2.32). It can predict f_r of an MPA with relative %error of 1.6% and 0.1% for superstrate having permitivities of 3.66 and 4.7 respectively for considerably thicker superstrates. The presented theory is validated by developing prototypes and a good agreement between the measured and the simulated results confirm this premise. In essence, the technique presented is first of its type to anticipate f_r of an MPA covered with superstrate layers of relatively higher permitivities with very small relative %error than the previous works. An algorithm to integrate the developed model with any standard microwave simulator is also proposed. Finally, the proposed theory is applicable for wearable sensors with antenna in it and covered with dielectric superstrate for protection from the environment.