A Novel Triple-Mode Bandpass Filter Using Half-Wavelength-Resonator-Coupled Square-Loop Resonator

Abstract

A novel triple-mode bandpass filter (BPF) using half-wavelength-resonator-coupled squareloop resonator is developed in this letter. The half wavelength resonator is applied to add an additional path, which increases a pole in the passband and a transmission zero in the stopband. Furthermore, the coupling scheme is used to accurately predict its desired performance. Compared to the conventional square-loop dual-mode filter, higher frequency selectivity and wider bandwidth are achieved. Finally, this filter is designed, fabricated and measured. Good agreement is achieved among the theoretical, simulated and measured results. All of these results validate our design idea.