Desenvolvimento de uma técnica numérica para análise de superfícies seletivas em frequência do tipo Absorve-transmite

Abstract

Modern wireless communication systems use various types of devices such as antennas, modulators, filters, detectors, absorbers and many other types. In particular, electromagnetic wave absorbers have become critical components in security, detection and imaging systems. The fundamentals of the absorbers are based on configurations that allow the control of the electromagnetic waves. They attracted considerable attention from researchers due to increased microwave absorption performance requirements, good performance in civilian applications and the emergence of new types of microwave absorbing materials, resulting in considerable progress. In this sense, the full-wave methods and numerical methods are usually used for the analysis of several parameters. They are used in many cases in the core of commercial software as well as in hybrid methods. The use of simpler numerical techniques allows an analysis of reflection and transmission behavior in a suitable way with good approximation mainly in cascade structures. In this work the absorber structure is composed of a conductive frequency selective surface (FSS) and a resistive FSS in which there is a d spacing between the FSS. The conductive FSS is formed by a FR4 dielectric with an electric permittivity of 4.4 and the geometries formed by conductive copper strips. Resistive FSS have an FR4 dielectric with an electrical permittivity of 4.4 and the geometries are formed by OhmegaPly 1A50PT (35 micron - 50 ohms / sq) resistive materials. In this thesis, a numerical technique for analyzing microwave absorbers integrated with frequency selective surfaces was developed. Conductive FSS and resistive FSS modeling were used, both using the equivalent circuit technique based on Marcuvitz equations. For the analysis of the set or cascade of the structures, the scattering matrix technique was used. Internal parameters of the method such as the coefficients of inductance and susceptance equations, resistance, inductive and capacitive reactances of the structures were analyzed in order to allow a better approximation to the simulations and measurements. The designed absorbers used cross-dipole geometry and square loop both designed and measured in the laboratory. The numerical analysis technique showed good agreement with the measured and simulated results of the structures proposed in this work as well as with other measured and simulated absorbers presented in the literature. Improvements and modifications can be adjusted for other applications, use with optimization techniques, hybrid algorithms and other periodic structure designs.