This paper investigates wireless systems aided by dual-polarized intelligent surfaces. We compare reconfigurable intelligent surface (RIS), which adjust their reflection matrices, with movable signals operating with fixed intelligent surface (FIS), which adjust the signal frequency while the surface properties remain fixed. For both RIS and FIS, we consider surfaces with a diagonal reflection matrix, named diagonal RIS/FIS, and surfaces with a reflection matrix not limited to being diagonal, named beyond-diagonal RIS/FIS. Movable signals with FIS always outperform RIS, achieving at least a fourfold gain. When transmitter and receiver polarizations differ, beyond-diagonal FIS further enhances performance.

翻译：本文研究了双极化智能表面辅助的无线系统。我们将可重构智能表面（RIS）与采用固定智能表面（FIS）的可移动信号进行了比较：RIS调整其反射矩阵，而可移动信号在表面特性保持固定的情况下调整信号频率。对于RIS和FIS，我们均考虑了反射矩阵为对角阵的表面（称为对角RIS/FIS），以及反射矩阵不限于对角阵的表面（称为超越对角RIS/FIS）。采用FIS的可移动信号始终优于RIS，至少能实现四倍增益。当发射端与接收端极化方式不同时，超越对角FIS能进一步提升性能。