Compact tri-band bandpass filter based on quarter-wavelength resonators

Abstract

In this work, a planar microstrip tri-band filter based on quarter-wavelength resonators is presented, which allows independent control of the positions of all three passbands. Furthermore, the topology of the filter provides five transmission zeros and thus results in a highly selective response in all passbands. A synthesis procedure of the filter is presented and used to design a tri-band filter which operates at WLAN frequencies of 2.4/3.5/5.2GHz. The designed filter outperforms all other state-of-the-art tri-band filters in terms of compact size, high selectivity and transmission, and return-loss characteristics. Copyright © Taylor and Francis Group, LLC.