Compact,low return-loss,and sharp-rejection UWB filter using Sierpinski carpet slot in a metamaterial transmission line

Abstract

In this paper, a novel ultra-wide band (UWB) bandpass filter (BPF) and its equivalent circuit model are presented by etching a Sierpinski carpet slot on a single negative metamaterial (MTM) transmission line (TL). The MTM TL, demonstrated with negative permeability within two bands, consists of a Koch slot etched in the ground plane and a series capacitive gap etched in the upper stepped-impedance conductor line. The BPF is investigated in depth using full-wave electromagnetic (EM) simulation, electrical simulation and extracted constitutive EM parameters. Different geometrical elements on the overall performance of the filter are also systematically studied. A set of design guidelines and a simple method to extract lumped-element parameters are derived, which are of a practical value in future design. For verification, the developed BPF is fabricated and measured. Consistent results between simulation and measurement have confirmed the design, showing that the BPF with a relative bandwidth of 140.3% offers many advantages such as compact size, comparable low return loss and insertion loss, sharp and deep out-of-band rejection, and small variation in group delay.