A Miniaturized Dual-Band Bandpass Filter Using Open-Loop and SIR-DGS Resonators

A novel microstrip dual-band bandpass filter (BPF) is proposed in this paper. The designed BPF consists of an open-loop resonator on the top layer and defected ground structure (DGS) with a pair of U-shape stepped impedance resonator (SIR) on the bottom layer. The first passband at 2.4 GHz is determined by the SIR-DGS, and the second passband at 5.2 GHz is performed by the open-loop geometry structure. The measured results of the insertion losses are -1.83 dB and -2.4 dB at 2.4 GHz and 5.2 GHz, respectively. The return losses are -38.5 dB at 2.4 GHz and -20.8 dB at 5.2 GHz. The substrate material for fabrication is FR4 with permittivity of 4.4 and the thickness of 1 mm. The total area is 36.9 mm x 11.2 mm.