Modeling of Split-ring Type Defected Ground Structure and Its Filtering Applications

Susanta Kumar Parui, Santanu Das


A popular split-ring defected ground structure under a microstrip line is modeled here by an equivalent circuit. The frequency characteristics of the proposed unit cell show an attenuation zero close to its attenuation pole frequency. This is modeled by 3rd order elliptic lowpass filter. Accordingly, equivalent circuit is proposed and equivalent LC parameters are extracted. The influences of split-gap variation of the DGS unit on pole and cutoff frequencies have been investigated. Two DGS cells with different pole frequencies cascaded underneath a microstrip line realize a sharp and deep lowpass filter. The passband insertion loss has been reduced by using a high-low impedance line in place of the standard line. A prototype filter has been fabricated with Arlon substrate. The simulated S-parameters are compared with its experimental measurement results.

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