Transmission Lines Terminated With LC Resonators for Differential Permittivity Sensing

This letter presents a differential microwave permittivity sensor based on the reflection coefficient of microstrip lines terminated with series LC resonators. A 50 Ω resistor is considered in series with the resonator. At resonance, the transmission line experiences a matched load causing a reflection zero. Two identical sensing elements are used for differential sensing, providing the possibility of simultaneous two samples detection. A prototype of the sensor is fabricated and measured around 2 GHz for validation of the differential sensing principle.