Multifunctional broadband bidirectional electromagnetic modulation using asymmetrically biased metasurface

This paper presents a method of utilizing asymmetrically controlled PIN diodes to design a multifunctional active broadband metasurface with tunable reflectance, transmittance, and absorptance, thereby enabling bidirectional radar cross-section (RCS) control. The metasurface comprises an ABA tri-layer structure with PIN diodes asymmetrically biased in the top and bottom layers, acting as variable impedance elements. An equivalent circuit model (ECM) guides the design to achieve a broad operational bandwidth of 6−14 GHz (~80% fractional bandwidth). By varying the direct current (DC) bias voltage from 0.4 V to 0.6 V, the metasurface supports three operational modes: near-perfect reflection (>95% reflectance), near-perfect absorption (>90% absorptance), and partial transmission, with RCS reductions up to 15 dB for forward and backward incident electromagnetic waves. The fabricated array, controlled by DC biased voltage, demonstrates switchable characteristics across these modes, validated through full-wave simulations and measurements. Compared to conventional tunable metasurfaces, the proposed design offers broader bandwidth and enhanced tunability, making it ideal for electromagnetic shielding, stealth technology, and adaptive wireless systems.