Microwave filter using defected ground plane technique

Abstract

The Defected Ground Structure (DGS) is used to modify the guided wave characteristics and change the propagation constant. This structure is motivated by a study of Photonic Band Gap (PBG) to change guided wave properties. Defected ground structure (DGS) is made by etching any defected pattern in the ground plane. These designs have typical low-pass properties. The basic DGS is composed of two wide defected areas and narrow connecting slot, which are the sources of the equivalent L-C components. In order to improve the performances of the proposed periodic DGS, a uniform periodic DGS circuit and two improved periodic DGS circuits are designed. For the two latter designs of the periodic DGS, the dimensions of the defected shape are varied proportionally to the relative amplitudes distribution factor 0.8. These designs are fabricated and measured. By the experiment, the measurements show that the latter exhibits more excellent performances by suppressing ripples and enlarging stopband bandwidth.