Design of dual-band bandpass filter using stepped impedance resonator and defected ground structure

This article presents a novel microstrip dual-band band-pass filter (BPF) comprising a symmetrically-bent, open-loop, square-ring stepped impedance resonator (SIR) at? the upper surface and a symmetrical U-shaped defected ground structure (DGS) oil the lower metallic ground plane. A center frequency of 2.45 GHZ is obtained for the first passband of the BPF by adjusting the dimensions of the SIR, while a center frequency ranging from 5 to 7 GH,7 is obtained for the second pass-band h), adjusting the dimensions of the DGS unit. The experimental and simulation results demonstrate that the insertion losses of the BPF art, -1.4 dB at 2.45 GHz, -1.3 dB at 5.75 GHz, and -4.1 dB at 5.2 GHz. The characteristics (of the proposed BPF with and without the DGS unit are compared, and the dependency of the second rcsonance frequency oil the dimensions of the DGS unit is discussed. Finally, the effectiveness of etching an additional DGS unit beneath the feed lines to suppress the high out-of-band harmonic frequencies is also demonstrated. (c) 2007 Wiley Periodicals, Inc.