Bandpass filter with generalized multiple-mode ring resonator configuration

A new generalized multiple-mode ring resonator configuration is proposed for bandpass filter design. The building block is a shorted half-wavelength ring. A quintuple-mode ring resonator bandpass filter is implemented for demonstration. Its entire circuit area is only 72% of that of a conventional dual-mode ring resonator. Coupling matrix method is employed for determining the inter-resonator coupling and synthesis of the passband response. In addition to a transmission zero created at the higher passband due to inductive cross coupling, two zeros near the passband are generated by source-load coupling. The measured results show good agreement with the simulation.