Multi-Bit Electrically Reconfigurable Circularly Polarized Reflectarray Elements Based on Pancharatnam-Berry Phase Principle

PIN diode-based reconfigurable reflectarray antennas have gained attention for their flexible beam-steering, simplified design, and cost effectiveness. However, many existing designs offer only 1- or 2-bit phase reconfigurability, limiting radiation performance. In this letter, we present Ku-band reflectarray elements with both 2-bit and 3-bit electrical phase control for circular polarization. By leveraging the Pancharatnam-Berry phase principle, dynamic phase control is achieved through PIN diode switching. The proposed design is validated using a waveguide simulator (WGS), which confirms the 2-bit phase responses and shows excellent agreement with full-wave simulations. Measured results demonstrate 2-bit phase quantization over an 11.1-12.5 GHz range (11.9% bandwidth) with insertion losses below 1.0 dB and cross-polarization levels under -15 dB. Furthermore, simulated performance of the 3-bit element reveals consistent 45° phase intervals. To verify array-level performance, 16×16 RRAs based on both 2-bit and 3-bit elements are implemented. This multi-bit reconfigurable strategy enhances reflectarray performance and offers increased design versatility for advanced Ku-band applications.