Design and characterization of the double‐layered defected ground structure transmission line with less radiation loss

A double‐layered DGS transmission line is proposed with a smaller DGS size and less radiation loss. Changing the air boundary to a dielectric boundary reduces the effective electric length at the DGS aperture area. An equivalent circuit model is introduced to analyze the DGS transmission line and the resonator circuit designs. Due to the increase in the effective dielectric constant, the proposed structure can be realized with less sensitivity to metallic environments. From the experimental results, the proposed double‐layered DGS can achieve a reduction of 90.1% in size and insensitivity at up to 5 mm of separation from the DGS aperture to the metallic plate.