Microwave resonators and their use as measurement instruments and sensors

Microwave resonators of very high Q-factors, as high as 109 , can currently be manufactured. In this paper, an overview of different resonant structures used for measurements of dielectric properties of materials at microwave frequencies, and that can be as electromagnetic sensors of other physical quantities such as humidity, chemical reactions and level of paramagnetic impurities has been presented. Potential applications of microwave are not widely known outside the microwave community, and hence a goal of this paper is to disseminate the information to a wider engineering community