Sistema de balanceamento e casamento de impedâncias para irradiadores de faixa ultra larga

Abstract

This work presents the construction and evaluation of an excitation system of an equiangular spiral antenna for wide band operation. Antenna analyzes show the potential to operate at large bandwidths with moderate variation in their characteristics, as impedance and gain. However, the same analyzes conclude that is necessary to design and model a structure that provides it is properly excitation allowing the system to extract these advantages. The study of the Tschebyscheff polynomials for the impedance matching and obtaining the smallest reflection coefficient, method applied in balun design. It was based on the idea of using a microstrip line and deduced the equations from the model of its ground plane to reach the most suitable impedance matching structure. Several simulations of the antenna and balun were made in the software Comsol Multiphysics®. The results of input impedance and reflection coefficient showed that the antenna shape, along with the balance of the currents at the feed point, provides the characteristics required for operation over a wide frequency range.