Coplanar Waveguide Dual-Band Bandpass Filter Using Stepped-Impedance Square Ring Loaded Resonator

A novel dual-band bandpass filter (BPF) is developed by using the proposed coplanar waveguide (CPW) stepped impedance square ring loaded resonator (SI-SRLR). To construct two passbands, the resonant property of the presented SI-SRLR is firstly investigated. Then, two coupled resonators are used to constitute a dual-band BPF with the center frequencies at 2.4 GHz and 5.8 GHz. Besides, an additional short-circuited conducting stub is introduced between two resonators to prevent excessive coupling to obtain moderate bandwidths. Furthermore, multiple transmission zeros are produced at each side of passbands, which highly improve the selectivity of the passband and the attenuation in stopband. Good simulated results demonstrate the benefits of the proposed resonator and design method.