A novel microstrip BPF designed using triangular open-loop resonators and a folded-line-shaped defected ground structure (DGS) is proposed. By appropriately choosing the tapping positions of the resonator's feed lines, the created transmission zeros can be properly located so as to improve the skirt rejection. Also, with the addition of the newly designed folded-line DGS, the skirt rejection at the upper passband edge can be increased. The results demonstrate that such a filter design can achieve a compact circuit size and a sharp passband skirt, while retaining the insertion loss at a relatively lower level.
Microwave and Optical Technology Lett., 48(1): 43-47