Concentric Square Rings with Phase Delay Line Design for BST Reconfigurable Reflectarray Technology

This paper presents a reconfigurable reflectarray unit cell design that incorporates Barium Strontium Titanate (BST) technology for satellite applications. The design proposes three concentric square rings, two of which are divided by a gap and equipped with phased delay lines. This configuration aims to achieve a broader phase range and lower reflection loss. The BST layer, a thin film, is capacitively loaded with a narrow gap within the slot of the innermost square ring, while a few phase delay lines are connected to the outermost square ring. By tuning a DC-bias voltage across the gap, the permittivity of the BST layer can be modified as an integrated capacitor. The paper presents the step-by-step design process of this unit cell, including the selection of substrate material and thickness, analysis of design to increase the phase range, and analysis of the effective biasing line design. The achieved overall phase range is 290.54°, with a maximum reflection loss of 13.653 dB at 13.4 GHz (Ku band), making it suitable for satellite applications.