A study on ferroelectric phase shifter with photonic-bandgap (PBG) structure

In order to get the low-loss microwave tunable device, we adopted the photonic-bandgap (PBG) structure based on BST thin films on MgO (001) single crystal substrate. We designed and fabricated a microstrip ferroelectric phase shifter with PBG structure for microwave integrated circuit. The proposed multilayer PBG structure consisted of microstrip tunable interdigital (IDT) patterns atop BST thin film and two square defected areas in the ground metallic plane. To analyze microwave characteristics of the proposed multilayer PBG structure, finite-element-method (FEM) was used. The fabricated phase shifter shows 103 degrees differential phase shift, 3.3 dB insertion loss, and return loss of better than 20 dB at 20 GHz with dc-bias variation from 0 V to 110 V.