Microwave Sensor for Detection of Solid Material Permittivity in Single/Multilayer Samples With High Quality Factor

In this paper, a planar microstrip sensor based on a band-stop filter for determining relative permittivity of solid materials is presented. The proposed sensor has been composed of the structure of meandered microstrip line with a T-shaped resonator and an interdigital structure that is connected ground by via. Interaction between the T-shaped resonator and the interdigital structure is caused to increase electric field intensity and the high field increase the sensor sensitivity and resolution. The microwave sensor by using single layer technology is fabricated on the substrate RO4003. The samples of FR4 and RO4350 in single and double layer forms as multilayer are placed on the sensor, and the sensor is demonstrating different resonance frequencies. The relationship between changing the resonance frequency and variation of the relative permittivity is linear, and it determines unknown materials' dielectric characterizations. The permittivity of samples changes from 3 to 11; therefore, the resonance frequency varies from 3.7 to 5.65 GHz linearly. The proposed sensor shows improvement relative to other similar works in the fields of sensitivity and quality factor.