Sensing Applications Based on Cavity Perturbation Method - A Proof of Concept

A new category of sensing devices based on perturbation of a resonant circuit or cavity is presented in this paper. The sensor uses a substrate integrated waveguide (SIW) resonator perturbed by the column length of a liquid-in-glass thermometer. Total 1.05°MHz/°C sensitivity is measured with contributions of 0.6 MHz/°C from a liquid-in-glass thermometer with 0.2 mm diameter of the ethanol column and 0.45 MHz/°C from the SIW resonator. Simulations based on liquid columns with diameters of 0.5 mm and 1 mm show that sensitivities at least one order of magnitude higher than values currently available from state-of-the-art SAW sensors can be achieved. A solar energy harvesting solution is also analyzed for increasing the reading distance in fully wireless sensing applications.