An Interdigital Capacitor Based Differential Microwave Sensor for Solid Measurement

This paper presents a novel differential design consisting of three interdigital capacitor structure to improve sensitivity and avoid environment interference. The frequency shift of the designed sensor was first simulated and then measured by locating materials with different dielectric constants. Region 1 was verified as the most sensitive area to distinguish different solid materials, and the sensor exhibits the ability to estimate defects on surface. The measured results also confirm its potential in thickness and loss tangent detection.