Fractally slotted patch resonator based compact dual-mode microstrip bandpass filter for Wireless LAN applications

A miniaturized dual-mode microstrip bandpass filter (BPF) based on fractally slotted patch resonator is presented in this paper. The proposed filter is centered at 2.4 GHz desirable for Wireless LAN applications. The dual-mode filter is realized using the fractally slotted structure on an octagonal patch resonator with perturbation. The design offers transmission zeros (TZs) at 2.19 GHz and 2.66 GHz on either side of the filter passband ensuring high selectivity. The locations of TZs from the center frequency can be adjusted by tuning the perturbation size. The filter is fabricated on a substrate with high permittivity and found to have a 3-dB fractional bandwidth (FBW) of 5% in the passband. Moreover, the measured minimum insertion loss is less than 0.91 dB and the return loss is greater than 23 dB in the passband. The prototype filter is fabricated and tested. Good agreement is accomplished between the experimental and simulation results. Furthermore, the footprint of the fabricated filter is about 0.416 lambda(g) x 0.416 lambda(g) where lambda(g) is the guided wavelength at 2.4 GHz. (C) 2019 Elsevier GmbH. All rights reserved.