Analytical Design of Phase Variation-Based Dielectric Constant Sensors

A phase variation sensor is designed in this paper for dielectric constant measurements of solid dielectrics. The sensor is designed using a coplanar waveguide (CPW) transmission line terminated with a semi-lumped LC resonator. The inductance (L) of the resonator is made of a thin meandered wire, whereas the capacitance is realized as the edge capacitance between a rectangular patch and ground metallization. By placing dielectric slabs with different permittivities on top of capacitive patch, phase of the reflection coefficient (S11) is modified, from which the dielectric constant of the material-under-test (MUT) is identified. A circuit-based analytical design procedure is developed for the sensor to optimize the sensing performance for an arbitrary operation frequency and dielectric constant range of the material-under-test (MUT). The design procedure is validated through EM and circuit model simulation as well as the measurement of a fabricated sensor prototype.