Miniaturized Dual-Mode Ring Resonator Bandpass Filter with a Wide Passband

Abstract

Dual-mode ring resonator filter is designed to have a relatively wide passband with a miniaturized circuit area. The miniaturization is achieved by folding the ring trace to a spiral configuration. The two degenerate modes are split up by an asymmetric inductive perturbation. As a result, the circuit area is only 29% of that of a conventional ring. The strong I/O coupling required by the wide passband property is implemented by adding an impedance transformer for matching the external quality factor (Q(ext)) with the circuit bandwidth. Measured results show good agreement with the simulation.