Arranjos de antenas de microfita com supercondutores sobre substratos anisotrópicos.

Abstract

Theoretical analyses of superconducting microstrip antennas and arrays are presented in this work. The properties of linear, planar and circular array structures composed of microstrip superconducting patches were investigated. In the study, the dielectric substrate layers were assumed to be isotropic or anisotropic, while the microstrip patch was considered to be made of a very thin superconducting film. In this analysis two techniques were used in order to determine the Green's function of the structure in the Fourier domain. These techniques are Hertz vector potentials and immitance approach. It should be pointed out that the analysis based on the immitance approach is suitable for the study of multilayered structure, because it is based on TE and TM equivalent circuits. Thereafter, numerical results for the microstrip patch antenna and arrays are obtained by using the moment method (Galerkin method). The analysis of the very thin superconducting microstrip patch is performed by using a surface impedance approach and the two fluid model. In this analysis, the substrate electric permittivity and the Green's function expression of the structure are related to the operating temperature. For the considered microstrip antennas and array structures, numerical analysis were developed to determine the effect of the operating temperature on several parameters, such as: resonant frequency, bandwidth, quality factor, input impedance an radiation pattern. The results obtained in this work were compared to those available in the literature, for several particular cases. An excellent agreement was observed, showing that the proposed techniques are accurate and efficient in modeling superconducting microstrip antenna and arrays for microwaves and millimeter wave applications. Future works are suggested on the development of planar antennas with new superconducting materials, other patch geometries and feeding techniques.