Low-Profile Two-Dimensional Beam-Scanning Antenna Based on Reconfigurable Modulated Metasurface

A reconfigurable modulated metasurface (RMTS) based two-dimensional (2D) beam-scanning antenna is introduced. While the modulated metasurface (MTS) exhibits excellent low-profile characteristic, the challenge lies in implementing impedance reconfiguration at the unit-cell level. Under scalar modulation, the unit-cell design and feeding scheme of passive MTSs impose limitations on the performance of reconfigurable implementations, particularly in terms of cost, cross-polarization, and gain. In this work, an impedance-reconfigurable unit-cell loaded with PIN diode is presented, featuring a large size to minimize the overall number of required unit-cells. Moreover, a side-feed configuration, coupled with optimized initial phase settings, is employed, effectively boosting gain and minimizing cross-polarization. The efficacy of the RMTS is demonstrated through beam scanning across two perpendicular planes. A prototype of the RMTS-based antenna has been constructed and tested, showing a realized gain of 19.7 dBi at 6.9 GHz, capable of scanning from −30° to 60° in one plane and ±45° in the other, with scanning losses of 1.7 dB and 2.3 dB, respectively.