Tunable Electromagnetic Gradient Surface for beam steering by using varactor diodes

In this paper, tunable beam steering has been realized by arranging Electromagnetic Band- gap (EBG) that has constant phase difference, Δφ. The proposed structure is the active periodic Electromagnetic Gradient Surface (EGS) that consist of the 4 by 4 matrix form of unit cells to easily control the several varactor diodes. The phase gradient ±120° of the proposed EGS is selected. Moreover this structure uses only one diode per four unit cells. The conventional loading of a single varactor for each of the unit cells of the EBG is overcome by connectdkgkding the unit cells to a feeding network directly without via. Thus, the EGS can steer reflected beam to -9° at Δφ = 120° and to +9° at Δφ = -120° by actively changing the biasing voltage of varactor diode.