Projeto de uma antena log-periódica com polarização linear desmontável aplicada para medir antenas na faixa de UHF

Abstract

In this work, the design and analysis of two log-periodic antennas will be presented, whereby one is linearly polarized and the other exhibits dual-linear polarization. Both radiators operate in the UHF band and can be applied to measure other antennas. The main motivation for this work is to overcome a current limitation of the Laboratory for Electromagnetics, Microwaves and Antennas (LEMA) of Campus Alegrete of Universidade Federal do Pampa (UNIPAMPA), since there is no wideband radiator that allows carrying out measurements in the range from 300 MHz to 1 GHz with linear or circular polarization. The work begins with a literature review that addresses mainly topics relevant to the subject discussed in this text. Subsequently, in Chapter 3, the design and electromagnetic analysis of the radiator with linear polarization will be presented, including the presentation of parametric studies carried out so as to allow optimizing the location of the excitation point and results obtained from these simulations. In order to obtain an antenna with circular polarization, parametric analyses for the radiator with dual-linear polarization will be presented in Chapter 4. The generation of circular polarization with such a radiator can be easily obtained by inserting a phase shift of ±90◦ between the fields of each polarization, which can be realized by means of a 90◦ hybrid coupler. In Chapter 5, the process of prototyping and measuring the linearly polarized antenna is described, including details of the techniques employed to allow easy assembly of the structure. The design strategy has been validated by comparing simulated and measured results, whereby good agreement between the S11 results has been verified. Finally, this work yields the first log-periodic radiator designed at LEMA, which will allow measuring other antennas with linear or circular polarization in the UHF band. Keywords: antennas, log-periodic antenna, broadband antenna, linearly polarized antennas.