Projeto e desenvolvimento de dispositivo de imageamento through-wall de alta resolução para identificação de características biométricas e bioestruturas com aplicações na segurança pública, defesa civil e defesa nacional
Rodrigues, Ramysés de Macedo
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Public safety is a fundamental right of every citizen and it is the duty of the State, as provided in our Constitution, being executed by the police forces at federal and state level. Defense is responsibility of the Armed Forces and civil defense actions, Fire Brigade and the similar associations. For an efficient service, these institutions need the appropriate technological infrastructure. Thinking about this, and within the premises of the Graduate Program in Biotechnology, a device based on radar architecture, capable of detecting human individuals (biological structures) that are hidden by an opaque bulkhead, such as a allowing basic biometric measurements to be extracted from the generated images. The project was thought considering the Brazilian context, its most used civil construction materials and urban composition. The work begins with a review of the electromagnetic theory and its properties, useful to the application in the present project. A bibliographic survey on the electrical characteristics of building materials used in Brazil was carried out and their influence on the propagation of radio signal is analyzed. Discussions about basic radar architectures, their principles and main characteristics were the subject of studies, where the classic FMCW-radar (Frequency-Modulated Continuos Wave) was delineated and chosen as the basis of this project. The electrical characteristics of the outermost human biological tissue, the epidermis, were analyzed through databases available in the literature, and its constitutive parameters have wide variation with frequency, but their echo response still allows detection. The performance of the device was evaluated through the implementation of a virtual environment, consisting of a set of compact antennas, aiming at the portability of the equipment and the performance in the chosen frequency of operation, and walls with configurable positions and electrical characteristics. The use of the Yee algorithm allowed the visualization of the electromagnetic signals and their interactions with the media in the virtual environment, where Maxwell's equations were implemented through the Finite-Difference Time Domain (FDTD) technique, in 2-D. A block diagram of the electronic circuitry that will allow a physical assembly of the device is presented and evaluated along with the proposed image and enhancement algorithms. The results demonstrate that the project presents technical, budgetary and operational feasibility for its intended purpose. It is possible to detect biological targets (human beings) even hidden by walls, and also to estimate anthropometric measurements through the generated images. In comparison with its Israeli counterpart, the proposed device has several advantages, especially in the cost of manufacturing a unit, being more compact, more robust and simple operation.