Analysis of different types of coupling for microstrip ring resonator

Microstrip ring resonators are frequently employed RF/Microwave circuits. Resonator structures such as rectangular, circular and ring resonators have been widely studied in filters and oscillators as well as for dielectric material characterisation. This paper deals with the design and study of coupling efficiency between the microstrip feed lines and the annular microstrip ring elements. Simulation models are developed for different ring resonator coupling techniques: Loose-coupling, Enhanced-coupling and Matched-stub-coupling technique. Finally, a comparison among the developed simulation models is performed in order to evaluate each technique and conclusions are extracted.