Generation of Discrete Nondiffractive Beams Based on Programmable Metasurface for Multitarget Communications

In this article, a programmable transmissive metasurface is proposed for generating discrete nondiffractive beams, which can provide similar power for multiple targets. The phase distribution of the Bessel beam with arbitrary deflection is first calculated. Then, the obtained phase distribution is binary modulated to transform the Bessel beam with a continuous focusing line into a nondiffractive beam with discrete focusing lines. By imposing different coding matrices, the generated discrete beam can be deflected in any direction. Then, an array of 31\times 31 supercells is constructed and fabricated. For demonstration, discrete diffraction-free beams along three different transmission directions are discussed in Cases 1-3. From the simulated and measured electric field intensities, it is observed that the energy is concentrated at intervals and the main lobe of the beam shows obvious nondiffractive characteristics, proving that the proposed metasurface can produce discrete nondiffractive beam along any preset direction near 10 GHz. To verify the practicability and reliability of the proposed metasurface in wireless multitarget communication, microstrip patch antenna arrays are placed at multiple discrete focal points of the generated discrete beams (Cases 1 and 2). It is concluded that the communication quality is approximately equal even if the front-end receiving target blocks the back-end target physically, which solves the challenge of path loss. Therefore, the proposed design is expected to be utilized in secure communication, energy transmission, and other scenarios.