Banca de QUALIFICAÇÃO: JOAO GABRIEL COSTA RODRIGUES

Development and Characterization of Passive Planar Temperature Sensors Based on Frequency-Selective Surfaces

FSS, microwave sensor, thermal sensing, resonant frequency, low cost.

This work presents the development and experimental investigation of passive temperature sensors based on Frequency Selective Surfaces (FSS), exploring the electromagnetic response of resonant structures to temperature variations. The sensors' operating principle relies on the temperature dependence of the dielectric substrate's electromagnetic properties—specifically its permittivity—which results in shifts in the structures' resonant frequencies. This approach enables the development of passive sensing devices where temperature-related information is derived from the FSS frequency response, facilitating their use in remote sensing and monitoring applications. The research encompasses the design, numerical analysis, fabrication, and experimental characterization of various FSS configurations, aiming to investigate how geometric and electromagnetic parameters influence the thermal response. Initially, the structures are analyzed via simulations using Ansys HFSS to understand their resonant behavior and identify configurations suitable for temperature sensing. Subsequently, prototypes are fabricated and experimentally characterized under various thermal conditions to evaluate the relationship between resonant frequencies and the applied temperature. Preliminary results show an approximately linear relationship between temperature and resonant frequencies within the 20°C to 100°C range. For one of the investigated configurations, thermal sensitivities of 0.625 MHz/°C and 0.750 MHz/°C were observed for the first and second resonant frequencies, respectively. These initial results demonstrate the proposed structures' ability to respond measurably to temperature changes and indicate the feasibility of using FSS as a platform for developing passive sensors. Thus, this work aims to contribute to the development of new passive temperature sensing strategies based on planar microwave structures.