Comparative Study of Various Microwave Sensors in Determining the Thickness of Dielectric Materials

Nondestructive measurement of thickness of dielectric materials is an important task for many industries including automotive, infrastructure, pipeline, etc. In this research, various microwave circuits, including microstrip line (MS-line), meander microstrip line (MML), complementary split-ring resonator (CSRR), ring resonator (RR), and microstrip antenna (ANT) used as sensors to detect the thickness of dielectric material. As an example five slabs of FR-4 used as a material-under-test (MUT), each slab has a thickness of 1.5mm and are stacked to achieve variable thickness of MUT. The measurement results of all these sensors when loaded with various thickness of MUT presented. It concluded from the measurement results that antenna and CSRR performed well as compared to the other sensors, and thickness of 0.1mm to 9mm can easily be detected using ANT or CSRR.