Ultra-Wideband Bandpass Filter With Coupled Step Impedance Resonator and Open-ring Defected Ground Structure

Abstract

In this paper, a compact ultra-wideband (UWB) bandpass filter based on coupled step impedance resonator (SIR) and defected ground structure (DGS) is proposed. The filter consists of a pair of coupled SIRs and an open-ring DGS. The filter presents a quasi-elliptic function response in which three transmission zeros improve the transmission characteristics of the filter. The simulated results show that the filter passband defined by $\mathbf{S}_{\boldsymbol{11}} \boldsymbol{< -10}\ \mathbf{dB}$ is from 3.58 to 12.57 GHz, and the insertion loss is less than 1.58 dB. In addition, the filter size is only $\boldsymbol{0.22\lambda }\mathbf{g}\boldsymbol{\times 0.38\lambda} \mathbf{g}$ at the center frequency of 8.075 GHz.