Circuit diagram of a single-mode microwave ring resonator

An electric circuit representation of a side-coupled single-mode microwave ring resonator is presented. The ring resonator is coupled to the feed lines along a quarter-wavelength of its side to exhibit a single-mode bandpass response with two transmission zeros. Using the properties and the circuit model of a coupled-line, the complete diagram of the ring resonator is derived. The diagram will be useful to construct mathematical equations to represent the ring resonator for future development of its synthesis. Example of utilization of the diagram is given to show its feasibility.