A Single-layer Dual-polarization 1-bit X-band Modular Reconfigurable Intelligent Surface based on Fan-in Style Bias and Control Integration

This communication presents a single-layer, 1-bit, dual-polarization, modular reconfigurable intelligent surface (RIS) operating at X band, aimed at developing a cost-effective and universal RIS design solution. The modularized architecture of the single-layer RIS, enabled by a fan-in style bias technique, facilitates scalability and efficient control. A folded ground design achieves the single-layer configuration. The dimensions of the nested patch resonator are fine-tuned to minimize reflection amplitude differences. Inspired by fan-in packaging techniques, the bias lines are routed to the vertical connectors at the center of each unit group, avoiding extra area usage and forming the modular structure of the RIS for large-scale splicing. The performance of a 16 × 16 modular RIS was evaluated, demonstrating a maximum gain of 22.9 dBi and a beam scanning range of ±60°. Compact connection methods, including solder ball-like and pin grid array-like connections, are discussed and demonstrated in light-emitting diode arrays. These enable direct mounting of modular RIS, thereby reducing the system profile. Additionally, integrated D flip-flop control is validated for digital control-only systems, providing an option to integrate all components onto a single-layer board. These designs may offer a low-cost and flexible RIS design solution.