Microwave ring resonator with a quarter-wavelength coupled-line integration

This paper proposes a novel topology of one-wavelength microstrip ring resonator which integrates a single quarter-wavelength parallel coupled-line as one of its input/output points. Such topology results in a single mode response with zero transmission at both sides of the bandpass. A complete simplified diagram of the proposed topology is developed and presented in this paper. An example of realization is performed using microstrip technology on FR4 epoxy glass substrate to verify the feasibility of the proposed idea. Measured results show good agreement with the ones from simulation.