A new bandstop filter using artificial defected ground structures with compact size and low radiation

A novel defected ground structure (DGS) with mushroom structures is proposed. This structure is a three-layer structure composed of a patterned metal plane on the top layer and mushroom structures occupying the second and the third layer. It can be applied to a multilayer structure with lower radiation compared with conventional DGS due to its well shielding. Based on slow wave characteristic, this proposed structure possesses a more compact size than conventional DGS does and still keeps resonance property. A bandstop filter is fabricated on FR4 board and the center frequency is designed at 3 GHz. It is shown that the filter has a size reduction over 28.7% in contrast to bandstop filter with conventional DGS.