Microstrip Whispering-Gallery-Mode Resonator

Whispering gallery modes (WGMs) were exited in a new type of microstrip circular resonator formed under a conducting disc placed directly on or above a continuous dielectric layer. Resonance frequencies, quality factors, and distributions of the microwave field for different WGMs have been studied numerically and experimentally as a function of distance between metal and dielectric. An unloaded Q-factor up to 890 was obtained using polished copper disk and layer of single crystalline sapphire. Generalization of the known condition of the excitation of the WGMs in a dielectric medium is proposed.