Abstract-In this paper, the effect of both uniaxial anisotropy in the substrate and air gap layer on the resonant frequency and bandwidth of circular microstrip patch are investigated. The problem is rigorously formulated based on the spectral domain technic in conjunction with Galerkin approach for computing the resonant frequency, half-power bandwidth, and radiation field of a tunable circular patch antenna which is printed on isotropic or uniaxial anisotropic substrate. The TM set of modes issued from the magnetic wall cavity model theory are used to expand the unknown currents on the patch. Resonant frequency shift due to uniaxial anisotropy is firstly investigated for different anisotropy ratio values of substrate. Then, the effect of inclusion of air gap layer inserted between anisotropic substrate and ground plane on the resonance characteristics is also investigated. The results obtained from this approach are in very good agreement with the experimental results available in the literature.

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In the present paper, a rigorous full-wave analysis for determining the resonant frequency and half-power bandwidth of covered circular microstrip patch antenna is presented. Green's functions of the structure are determined in Hankel transform domain. Galerkin's is used in the resolution of the electric field integral equation. The TM set modes issued from the cavity model theory are used to expand to unknown current on the patch. For an isotropic substrate, it is demonstrated that the bandwidth decreases with increasing ratio of superstrate-substrate thickness for high permittivity and low thickness of superstrate. Also, we show that the resonant frequency and bandwidth are highly dependent on the permittivity variations along the optical axis. The validity of the results is tested by comparing results with those published in the literature. Also, numerical results for the variation of the resonant frequency and half-power bandwidth of the substrate-superstrate configuration for high order modes, and for several values of substrates thickness are presented.

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In this paper, an electromagnetic approach based on cavity model in conjunction with electromagnetic knowledge was developed. The cavity model combined with London's equations and the Gorter-Casimir two-fluid model has been improved to investigate the resonant characteristics of high Tc superconducting circular microstrip patch in the case where the patch is printed on uniaxially anisotropic substrate materials. Merits of our extended model include low computational cost and mathematical simplify. The numerical simulation of this modeling shows excellent agreement with experimental results available in the literature. Finally, numerical results for the dielectric anisotropic substrates effects on the operating frequencies for the case of the superconducting circular patch are also presented.