volume | PIER Journals

Abstract

This paper introduces a spatiotemporal encoding method based on metasurface that enables precise frequency control and functional switching of radiation beams. The metasurface is configured with subarrays, and each subarray is designed to reflect a specific frequency, thereby achieving unique multi-target signal diversity. By manipulating the spatiotemporal phase of subarray elements, the metasurface can generate far-field radiation patterns with beam characteristics of consistent beam angle at different distances, or beam characteristics of consistent distance with different beam angles. The radiation energy distribution at harmonic frequencies is verified to remain symmetry under various 1 bit spatiotemporal encoding matrices, while the symmetry is verified to be broken by 2 bit spatiotemporal encoding matrices. An optimization method of genetic algorithm (GA) improved binary particle swarm optimization (BPSO) based on 2-bit-coding is thus developed to optimize the spatiotemporal modulation of the metasurface subarray. The GA with the advantage of the crossover mutation operation is utilized to enhance population diversity and thus prevent the algorithm from falling into local optimality with improved search efficiency in high-dimensional discrete space. The optimization method balances different performance parameters and can achieve unique multi-target signal diversity, thereby improving the metasurface's ability to dynamically control and manipulate energy distribution. Using a 1-bit cross-switching mechanism with a duty cycle of 50%, the metasurface can suppress specific harmonic frequencies on the line of sight to less than -60 dBi while keeping the sidelobes below -20 dBi. The technology can precisely control the harmonic energy distribution while allowing beam at specific harmonic frequencies to be absorbed or reflected, which realize advanced breakthrough for effective selective stealth. Simulation results validate the proposed digital encoding optimization method, and the mainlobe gain of the metasurface harmonics is obtained to be more than 20 dBi. This paper algorithmically improves the beam gain of the metasurface and explores the versatile applications of spatiotemporal metasurfaces.

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Dr. Xueyan Wang

Dr. Rui Xi

Dr. Xinan Hou

Mr. Huanran Qiu

Dr. Zihui Liu

Dr. Dexiao Xia

Dr. Xiaokui Kang

Dr. Shiyun Ma

Dr. Yuanhao Zhang

Prof. Long Li

Prof. Lan Lan

Dr. Guisheng Liao