Proposta de antena para aplicação em radar de abertura sintética na banda C embarcada em veículo aéreo de pequeno porte

Abstract

This work presents an antenna design for the application in C-band synthetic aperture radar to be installed onto a small aircraft for operation with dual-linear polarization at 5.8 GHz. The objectives of the study are to propose solutions for environmental monitoring through remote sensing by active devices; characterization of a synthetic aperture radar remote sensing system; a description of a front-end SAR system for installation onto small aircraft; and the proposal of an antenna topology for operation at 5.8 GHz with dual-linear polarization. The work methodology is based on a literature review process on remote sensing systems and antenna design, and analysis with electromagnetic simulation with Ansys Electromagnetics Suite 2016 software. Active and passive sensors are compared, focusing on the former, for analysis of remote sensing systems with side-view approach. A discussion about synthetic aperture radars is developed with the presentation of some SARtype image construction parameters, such as image resolution, acquisition modes, and phase and polarization attributes of the signals. Validated designs of small aircraft embedded systems for SAR-type image acquisition, presented in the literature, are discussed. The basic antenna theory is exposed, bringing concepts of antenna arrays and polarization of electromagnetic waves. These are discussed as microstrip, slot-coupled antenna technologies, and resonant cavity modeling principles. An attempt to summarize some main parameters of an airborne SAR system is presented to support the following steps of this research. The first attempt to meet the design specifications was made with the simulation of slot-coupled antennas. The second part of the research was focused on the development of antennas based on resonant cavities composed of lateral walls in SIW technology and with an radiation slot. Parametric studies were carried out to understand the impact of the distribution of metallic vias and the radiating slot in the structure. The pins were placed uniformly and non-uniformly along the walls of the resonant cavity. In addition, studies of the length and width of the slot have been carried out. All the analysis considered the conditions of cross-polarization at the operating frequency of the system. Following single element design, antenna arrays were proposed. Two-element and four-element arrays have been studied. The last part of the research consisted of building prototypes to validate the concepts. A two-element array was fabricated along with the feeder. Some problems in the prototyping steps have been identified and are discussed in this work.