MODELING OF QUASI-ELLIPTIC LOW PASS FILTER USING TWO CONCENTRIC RECTANGULAR SPLIT RING DEFECTED GROUND AND MICROSTRIP STRUCTURES

摘要

The shape of a popular split-ring defected ground structure (DOS) is modified by etching two concentric split-ring defective pattern which have different size and inverse split direction in the ground plane underneath a microstrip line. The frequency characteristics of proposed DGS unit show an attenuation zero close to the attenuation pole frequency. As a result, better transition sharpness is observed. An equivalent lumped L-C network is proposed to model the introduced DGS unit and corresponding L-C parameters are extracted. A 3rd order quasi-elliptic lowpass filter is designed by cascading the three investing DGS units under High-Low impedance microstrip line and the generated first harmonic has been removed with the help of defected microstrip structure (DMS) underneath the cascading DGS unit.