Planar WGM Resonator with High Dielectric-Constant Ceramic Slab for Sensing Applications

In this paper, a ceramic slab with high dielectric constant (ε
r
= 60) is incorporated in a printed ring resonator to realize a planar and compact sensing structure that supports higher order whispering gallery modes (WGMs) at microwave frequency band of 16 to 26 GHz. As the slab relative-permittivity increases, the resonator effective permittivity increases, and thereby higher order WGMs of high-quality factor are induced in the operating frequency band of the structure. Some electromagnetic features of the proposed structure are discussed to show its potential for many sensing applications including the characterization of aqueous solutions.