Quasi-lumped multimode stripline resonator and filter with good stopband performance

A novel 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 the problem of electromagnetic compatibility. Due to features of the resonator's structure, several higher modes do not excite that significantly improves the performance of the filter's stopband. The resonator advantages are proved on the bandpass filter (3.1…10.6 GHz) with a small overall size (0.19λ₀ × 0.11λ₀ × 0.11λ₀) and a good stopband performance (first spurious band locates at 29 GHz and suppression is 70 dB).