Análise da determinação da constante elétrica de materiais sólidos e líquidos usando parâmetros de transmissão na faixa de microondas

Abstract

With the rapid growth of technology, it has become necessary to develop sensory devices for the control and automation of various agricultural, pharmaceutical and food processes in order to better understand the dielectric properties of materials and measurement techniques. This work presents an investigation and construction of an electromagnetic sensor system based on planar and non-planar antennas that are used to evaluate impurities in solid and liquid substances according to the quality of transmission between them. For this, a dedicated configuration was implemented with tests in several frequencies, to monitor the behavior of the transmission variation between the antennas using the free space method. Transmission analysis was also performed between the sensors, varying the angles of transmitted signal incidence and distance. The proposed sensor system was tested at several frequencies resulting in different sensitivity values. The prototypes were constructed and tested to analyze the dielectric effects of impurities in liquid substances of Epocler, NaCl and C2H4O2 and solid in medicaments such as tablets and capsules of different sizes and weights. The methodology used a simple technique to calculate the parameters of scattering [S] in solids and liquids and with its processing to obtain the dielectric properties of the materials considered. In addition, a mathematical model is presented for the transmission parameters related to the dielectric constant εr. In the experimental procedures, the parameters [S] are collected in free space by the Vector Network Analyzer (VNA), using horn antennas and also planar antennas with metamaterial. The theoretical and experimental results are validated through metric coherences obtained.