Multi-Bit Phase-Coded Metamaterial With Honeycomb EM Structure for Scattering Manipulation Using Deep Learning-Based Method

A deep-learning inverse design method for generating multi-bit phase-coded metamaterials is proposed, aiming at broadband electromagnetic (EM) scattering manipulation with stable performance under oblique incidence. First, a deep learning-based approach for broadband phase gradient manipulation is analyzed using an equivalent circuit model (ECM), resulting in a bandwidth of 8.0–18.0 GHz. Then, to enhance performance under oblique incidence, a miniaturized folded tightly coupled dipole structure is proposed to suppress parasitic resonance. Furthermore, a design method combining deep learning with intelligent optimization algorithms is investigated to generate and optimize the dipole, ensuring stable operation at incident angles up to 45°. By leveraging ECM principles and previous EM knowledge, the physical dimensions of the unit cell generated by the deep-learning model are reduced from five to four parameters, and five-bit phase-coded unit cells are generated accordingly. Finally, a novel phase-coded metamaterial based on a honeycomb EM structure consisting of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$29\times 33$</tex-math> </inline-formula> unit cells, with a thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.36\lambda _{C}$</tex-math> </inline-formula> and a periodicity of 10.3 mm, is designed and simulated for radar cross-section (RCS) reduction under linear polarization (LP) incident waves. For demonstration, one prototype is fabricated and measured. The results indicate a broadband phase gradient from 8.0 to 18.0 GHz (76.9%) up to an incident angle of 45° in the case of dual LP. Regarding RCS reduction, the scattering far-field is reduced by more than 20 dBsm under LP normal incidence, with a 10 dBsm reduction maintained even at a 45° oblique incidence.