Dual-band bandpass filters based on dual-mode Hilbert fractal resonator

Abstract

We propose a compact planar dual-mode resonator based on a Hilbert fractal curve that operates at two arbitrary frequencies. The resonator is used to design two types of dual-band bandpass filters for WLAN applications, which exhibit a good trade-off between compact size and high performances, with the overall sizes ranging from 0.22 × 0.21 to 0.44 × 0.1 guided wavelengths and measured insertion losses from 0.38 to 2.5 dB. At the same time, the fabrication of filters is quite simple and requires no modifications in the ground plane or use of vias. In addition, the proposed resonator is used to design single-band filters as well. © 2013 Wiley Periodicals, Inc.