Projeto de concepção de microantenas planares em 2,45 GHz em substrato de LTCC para sistemas compactos e móveis.

Abstract

The advances in wireless Communications and electronics boosted the development of miniaturized system, becoming one of the main goals of research and application in the fieid of telecommunications. The miniaturization has a great importance in the integration of different equipments and cost reduction of products, resulting in an economic and technological development as the creation of new services. In this work are discussed some basic parameters of miero-antenna (or electrically small antennas) such as' input impedance, efficiency and bandwidth. Àlso were discussed some techniques used to reduce the antenna physical size such as^ insert short-circuits, change the thickness and dielectric constant of the substrate and make meander and gaps in the structure. It is made a brief introduction about the methods, analytical models (Cavity model and transmission line model) and the numerical methods (FDTD and FIT), shown their principal and how they can be used to design planar antennas. It is point out their vantages and limitations. The theoretical results were simulated using the CST Microwave Studio program. Based on the simulated results the geometries are designed in LTCC substrate. The LTCC substrate presents features (Dupont 951-AX, et = 7.8 e tanô= 0.006) that are electrical and mechanical compatible with applications in compact and mobile systems. The operation frequency adopted is 2.45 GHz, which is the used in free industrial, scientific and medicai (ISM • Industrial, Scientific and Medicai) applications. With the obtained results some models were designed with a surface area around 1.0 cm2. Between the better simulated models results three of them were selected and designed at the University of Sao Paulo (USP). The results were measured in USP laboratory and reproduced in the LEMA laboratory at UFCG.