Advanced 1-bit algorithmic approaches to PB phase metasurface optimization for radar cross-section reduction

The Pancharatnam-Berry (PB) metasurface has gained significant attention for its exceptional phase control capabilities. Various optimization techniques have been introduced, yielding diverse results even with the same unit cell design. We explored methods such as array pattern synthesis (APS) with particle swarm optimization (PSO), random sequence, specialized 0–1 coding, a genetic algorithm with a nonlinear fitting method, and PSO combined with far-field scattering and the annealing algorithm. Among these, the annealing algorithm demonstrated the most effective radar cross-section (RCS) reduction. The proposed design operates over a frequency range of 10–21.4 GHz, with a center frequency of 17 GHz. The 10 dB far-field RCS reduction bandwidth extends from 10.5 to 19.5 GHz, achieving a relative bandwidth of 52.94 % at normal incidence under linearly polarized normal incidence waves. For oblique incidence linear polarization, the metasurface maintains effective RCS reduction up to an incidence angle of 30°. The design utilizes unit cells with dimensions of 0.34λ × 0.34λ and a thickness of 0.145λ at the operating frequency. Experimental results closely match the simulated outcomes, validating the accuracy of the proposed design. Furthermore, compared to previously proposed methods, this approach demonstrates superior performance in bandwidth and RCS reduction. The coding metasurface comprises varying numbers of unit cells, with optimized configurations leading to low backscattering through mechanisms like polarization conversion, scattering and reflection. While the annealing algorithm demonstrates consistent RCS reduction (>10 dB) across the entire frequency spectrum, other coding strategies achieve < 10 dB reduction in specific bands. These findings illustrate the immense potential of the annealing algorithm for electromagnetic wave manipulation, with applications in stealth technology.