A Class of UWB microstrip bandpass filter using quasi-lumped element resonators with controllable stopbands

This paper presents an ultrawideband (UWB) resonator and a bandpass filter (BPF) consisting of quasi- lumped elements using a microstrip line (MSL). First of all, a resonator using a high-impedance inductive line and a gap capacitor is examined by an electromagnetic simulator. The simulated results of the resonator show UWB bandpass characteristics with two controllable stopbands by adjusting the element values and the length of the resonator. Secondly, an UWB-BPF using the presented resonator is proposed, fabricated, simulated and measured. It is confirmed that desired UWB bandpass characteristics are realized by controlling two stopband characteristics.