Coupling reduction between two elements of array antenna using U-shaped defected ground structure

This paper presents the U-shaped defected ground structure (DGS) which is incorporated into the groundplane of array antenna to reduce the coupling between antenna elements. The array antenna is constructed of two layers of flame resistant (FR) 4 epoxy dielectric substrate with the thickness of each layer of 1.6mm. The U-shaped DGS is placed at the bottom side of second layer between two elements of array antenna located on the top side of first layer. A proximity feeding technique of microstrip line applied to feed each antenna element is positioned on the top side of second layer. By reducing the coupling which is generated due to the input power at both feeding ports, the radiation characteristics of array antenna can be improved. To demonstrate the feasibility of U-shaped DGS in coupling reduction, an array antenna without DGS is also investigated. The characterization results have verified that the U-shaped DGS is applicable to reduced the coupling at the resonant frequency of 2.38GHz up to 2dB and 0.88dB for simulation and measurement, respectively.