A novel compacted microstrip bandpass filter using stepped impedance resonator(SIR) and defected ground structure(DGS)

This paper describes a novel compacted microstrip dual-mode bandstop filter realized using stepped impedance resonator (SIR) and defected ground structure (DGS) with tuningrange from 2.65 GHz to 3.85 GHz. The proposed filter is composed of three resonators :a folded half wavelength SIR resonator and a T-type stub-loaded resonator on the top layer and a defected ground structure (DGS) resonator in the ground plane. DGS is used for its property of miniaturizing the size of microwave filter and also improving the mutual coupling between the resonators. In addition, the transmission zeros at each passband skirts can be controlled by tuning the proposed resonators. This filter gives an insertion loss of -0.46 dB, a return loss of -27.5 dB with a center frequency around 3GHz. The experimental and 3D EM commercial software HFSS simulated results on the filter are presented and discussed and good agreements are obtained between its measured and simulated S-parameters.