Multi-mode resonator for ultra-wide bandpass filter with good stopband performance

Abstract

A multimode resonator is proposed, containing five resonant modes that are incorporated in the passband forming. The structure is based on a dielectric substrate suspended in a metallic case that allows solving problem of electromagnetic compatibility. Due to features of the resonator’s structure, several higher modes do not excite that significantly improve the performance of the filter’s stopband. The resonator advantages are proved on the ultra-wide bandpass filter (101%) with small overall size (0.11λ0×0.06λ0×0.03λ0) and good stopband performance (first spurious band locates at 8 GHz, suppression is 80 dB).