Multifunctional Wideband Digital Metasurface for Secure Electromagnetic Manipulation in S-Band

Digital metasurfaces have attracted significant attention in recent years due to their ability to manipulate electromagnetic (EM) waves for secure sensing and communication. However, most reported metasurfaces operate at relatively high frequencies, primarily due to the constraints imposed by the physical scale of the dielectric substrate, thus limiting their full-wave system applications. In this work, a wideband digital reflective metasurface is presented for capable of dynamically controlling EM waves, with multifunctional applications in the lower-frequency S-band. The metasurface is composed of electronically reconfigurable meta-atoms with wideband characteristics, and designed by using trapezoidal and M-shaped patches connected by a pin diode. Simulation results show that the proposed digital metasurface could achieve wideband 1-bit phase quantization with a stable phase difference within 180 degree +/- 25 degree and small reflection loss below 0.6 dB from 2.72 to 3.25 GHz. To validate the proposed design, a 20x20-unit metasurface array was designed, simulated and fabricated. By dynamically adjusting the coding sequence, the metasurface could enable multi-mode orbital angular momentum (OAM) beam generation, dynamic beam scanning, and precise direction finding. These capabilities support secure sensing and secure communications through high-resolution target detection and anti-jamming beam steering, as well as physical-layer security. The proposed wideband metasurface may serve as an effective candidate for enhancing spectral efficiency and security performance in radar and wireless systems.