A Novel Ultra-Wideband Bandpass Filter Based on Multiple-Mode Resonators with Defected Ground Structure

In this paper, a novel ultra-wideband (UWB) bandpass filter (BPF) with excellent passband performance and skirt selectivity is designed and fabricated. The proposed UWB filter consists of dual symmetric multiple-mode resonators (MMRs) and four defected ground structures. Six modes, including three odd modes and three even modes, could be designed within UWB band, and two transmission zeros are at the lower and upper cutoff frequencies. The paper shows that even modes can be controlled flexibly, while the odd modes remain the same. The design of the proposed filter is confirmed by simulation with a fullwave electromagnetic simulator and the experiment. The passband of the implemented filter covers the range of 3.1-10.6GHz. A good agreement between the simulated and measured results is obtained.