Microwave and optical sensors applied to the dielectric characterization of liquids

Abstract

This project aims to introduce the candidate to the study of electromagnetic sensors based on the spectral interrogation technique, that is, by frequency or wavelength. Two types of sensors will be analyzed theoretically and experimentally, one operating in the microwave range (from 0.9 to 5 GHz) and the other operating in the visible, in particular red (660 nm).The microwave sensor will be based on PCB (Printed Circuit Board), microstrip technology, and will essentially consist of designing resonant structures with the highest possible quality factor (Q), fed by transmission lines in such a way that the resonance frequencies of these structures vary with the contact of liquids of different dielectric characteristics. More precisely, the variation in the resonant frequency of the resonator will permit to measure the relative electrical permittivity of the liquid under analysis. Schemes of one port (antenna) and two ports will be developed.The optical sensor will be based on the excitation of the resonance modes of a metallic surface when an optical beam illuminates it. These modes are called plasmons, and the sensors based on this phenomenon called SPR (Surface Plasmon Resonators). The Krestchmann configuration will be used, whose setup is implemented and operating at LEMAC (Laboratory of Applied and Computational Electromagnetism), in two interrogation modes: by angle of incidence and by wavelength.The respective measurements will be made using the developed microwave sensors and the SPR. We will adopt as a benchmark test the identification of ethanol adulteration when mixed with water, because it is a widely documented test.