Analysis of T-shaped defected ground structure (DGS) using closed-form expressions

We propose a T-shaped DGS which has a much wider range of gap capacitance than the dumbbell-shaped one. In addition, we provide closed-form expressions for the 3-dB bandwidth and radiation rate in terms of the equivalent circuit elements for conventional analysis. The expressions for the equivalent circuit values to realize a DGS having a specific bandgap center frequency; its bandwidth and radiation rate are also presented for easy design.