Dual-Orthogonal Polarization Amplifying Reconfigurable Intelligent Surface With Reflection Amplifier Based on Passive Circulator

This article describes the design of a dual-orthogonal $\pm$ 45 $^\circ$ polarized amplifying reconfigurable intelligent surface (RIS). To make possible the use of two orthogonal polarizations, an RIS architecture where single-port reflection amplifiers (RAs) are connected to the RIS antenna ports is considered. Instead of transistor-based RA design which exhibits narrowband amplification and strong input power-gain dependency, a circulator-based RA device is designed and used in this work, showing more stable gain for a wide range of input powers, and amplification within a certain working bandwidth. Furthermore, a 4 $\times$ 4 wideband antenna array (working around the frequency 3.5 GHz) which supports dual-orthogonal polarizations with high efficiency, high orthogonal port isolation, and low element coupling is also developed. The amplifying RIS exhibits reflection gain performance for different input power levels as expected, and within the working bandwidth 3.45–3.54 GHz and incidence/reflection angle range 0 $^\circ$ –25 $^\circ$ , guaranteeing the feasibility of operations with both the polarizations.