The field of reconfigurable antenna arrays and beamforming techniques is witnessing significant advancements, driven by the need for improved spectral efficiency, energy efficiency, and cost-effectiveness. Researchers are exploring innovative architectures, such as tri-hybrid beamforming and polarization-coding reconfigurable phased arrays, to enhance performance while reducing hardware complexity and power consumption. Additionally, the development of flexible XL-MIMO systems via array configuration codebooks is gaining traction, enabling cost-effective implementation and improved system performance. Noteworthy papers in this area include:

• A study on tri-hybrid beamforming for radiation-center reconfigurable antenna arrays, which proposes a novel optimization scheme to maximize spectral efficiency and energy efficiency.
• A paper on multi-resolution codebook design and multiuser interference management for discrete XL-RIS-aided near-field MIMO systems, which introduces a hierarchical beam training method and jointly optimized codebook construction to improve beam training performance and user fairness.
• A research on low-cost architecture and efficient pattern synthesis for polarimetric phased arrays based on polarization coding reconfigurable elements, which achieves low cross-polarization and sidelobe levels comparable to conventional architectures.
• A work on flexible XL-MIMO via array configuration codebook, which enables flexible XL-MIMO cost-effectively and improves system performance compared to conventional antenna selection schemes.