Six-Pole Dual-band Bandpass Filter for WiMAX Applications

Halimat Olamide Yusuf, Augustine O. Nwajana

Recent advances in multi-band wireless communication systems have driven the increasing need for dual-band bandpass filters. These types of filters are capable of isolating a small section of the frequency spectrum within a broader spectrum. Over the years, coplanar waveguide, microstrip, slotline, stripline, and other planar transmission line technologies have been widely employed in the design of microwave circuits and systems. This work employs a Folded-Arms Square Open-Loop Resonator (FASOLR) microstrip planar structure, designed and simulated using PathWave Advanced Design System (ADS). A third order (three-pole) single bandpass filter is transformed into a sixth order (six-pole) dual-band bandpass filter. The proposed six-pole dual-band bandpass filter is centred at 2.3 GHz, with a fractional bandwidth of 7% and produces two passbands centred at approximately 2.2 GHz and 2.4 GHz. The design is implemented on a commercially available Rogers RT/Duroid 6010LM substrate with a dielectric constant of 10.7, a loss tangent of 0.0023, a substrate thickness of 1.27 mm, and 35 micro meter copper cladding on both sides. The overall filter component has a compact footprint of 30.56 mm by 20.56 mm. The design is validated through comparison of circuit-level and electromagnetic (EM) simulation results, which show good agreement. The EM simulation responses indicate a return loss better than 10 dB on the first band and better than 19 dB on the second, and an insertion loss better than 1.5 dB, demonstrating its suitability for WiMAX applications.