Triple-Layer Versatile Reflection-Transmission Polarization Conversion Metasurface

In this paper, we propose a triple-layer multifunctional polarization conversion metasurface (MPCM) capable of switching between different polarization modes, including linear to cross-polarization and circular polarization for both reflection and transmission. The first layer consists of an orthogonal doubleslot square ring with a PIN diode inserted in one slot. The second layer is a diagonal double-slot square ring, and the third layer is a single-slot square ring. These layers are separated by two substrates, with each layer performing distinct functions for a linear incident wave, collectively enabling multiple polarization conversion capabilities. By dynamically controlling the PIN diode, we achieved asymmetric transmission and reflection responses. The results demonstrate that the metasurface can convert linear to cross-polarization (5.9-7.4 GHz), linear to circular polarization $(7.11-9.44 \mathrm{GHz})$ with an axial ratio (AR) less than 3 dB, and co-polarization (5.8-9.8 GHz) in reflection mode. In total, six different operating modes can be achieved. The performance of the metasurface has been validated through simulations and measurements. This structure has potential applications in radar, antenna, and wireless communication.