Design and Performance Analysis of Dual Resonance Reduced Size Reflectarray Unit Cells with Double Ring and Line of Symmetry

This paper introduces a novel design for a reducedsize reflectarray unit cell capable of dual-resonance operation, specifically targeted at 5 GHz and 6.5 GHz. The grid size of the unit cell is $0.283 \lambda \times 0.283 \lambda$, which is significantly smaller than the conventional periodicity of $0.5 \lambda \times 0.5 \lambda$. The design incorporates two square ring-loaded patches and two lines of symmetry, enabling dual-resonance performance at the desired frequencies. A comprehensive parametric study was conducted to investigate the effects of substrate and foam/air thickness on the optimization of the unit cell, using detailed simulations performed with the commercially available CST software. The fabricated design configurations were implemented on a substrate with a thickness of 1.57mm and 4mm using FR-4 and air respectively. Simulation results demonstrate that the proposed unit cell resonates at the target frequencies of 5 GHz and 6.5 GHz, achieving promising return loss (S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf>). Additionally, the reflection phase exhibits a wide dynamic range of 668 degrees and a bandwidth of almost 1 GHz. The reflection phase of the proposed unit cell remains stable up to a 20-degree incident angle in both elevation and azimuth, regardless of the polarization mode. This design offers a compact and efficient solution for dual-frequency reflectarray applications, with a potential for implementation in modern communication systems.