Low In-Band RCS Reconfigurable Metasurface With LP Feed for CP Transmission, LP Reflection, and Simultaneous Transmission-Reflection Modes’ Switching

This article introduces a novel 1-bit reconfigurable integrated transmission-reflection (RTRA) metasurface with low in-band radar cross section (RCS). The unit receiving layer in the x-polarization (x-pol.) direction consists of two pairs of goat horn structures with two p-i-n diodes loaded between them. By controlling the states of the p-i-n diodes, a 1-bit reflection bandwidth of 12.9% is achieved in the 00 and 11 states. In the y-polarization (y-pol.), the receiving layer consists of two pairs of rectangular branches with different sizes, achieving a 1-bit reflection bandwidth of 10.9% for static RCS reduction. The transmission layer is composed of a circularly polarized (CP) unit, achieving 1-bit x-pol.-CP transmission when the p-i-n diodes are in the 01 and 10 states. Compared to the RTRA unit provided in the literature, the proposed unit exhibits isolation greater than 60 dB between the x-pol. and y-pol., with a 1-bit reflection bandwidth exceeding 10%. In addition, it has the capability of converting linear polarization to CP, simplifying the feeding structure. The proposed units are arranged in a $12\times 12$ array. In the reflection mode, ±60° beam scanning in the E-plane and H-plane is achieved, with cross-polarization between 30 and 50 dB. The aperture efficiency (AE) is 23.02%. In the transmission mode, by the random sequential rotation technique (SRT), the axial ratio bandwidth is enhanced, and ±60° scanning is achieved in the $xo\textit {z}$ and $yo\textit {z}$ planes. The AE is 15.2%. In the transmission-reflection mode, arbitrary dual-beam scanning is possible. Furthermore, the proposed RTRA metasurface array exhibits in-band RCS reduction characteristics.

I. Introduction

The development of wireless technology has experienced rapid progress from 1G to 5G. The next-generation 6G technology presents even higher requirements. Faced with the explosive growth of network service demands in terms of time, space, and coverage, the goal of 6G technology is to achieve integrated communication across the satellite and ground [1], [2]. Each platform should have the ability to independently process data while also being able to collaborate with others. In this context, multibeam antennas have emerged as a powerful candidate solution. Among them, the reconfigurable transmission-reflection integrated (RTRA) metasurface enables multibeam communication, allowing for simultaneous communication with multiple ground and space stations at the same time and frequency. Circularly polarized (CP) beam scanning characteristics are required for satellite communication, while linearly polarized (LP) beam scanning characteristics are needed for ground communication. In this context, the metasurface needs to achieve LP-to-CP transmission and LP-to-LP reflection modes.