Broadband transmission-type 1-bit coding metasurface for electromagnetic beam forming and scanning

Coding metasurfaces make it possible to manipulate electromagnetic(EM) waves digitally by means of several discrete particles.Hence, there have been rapid advances in this field recently. Here we propose a novel design of a broadband transmission-type coding metasurface, which is valid to both x-and y-polarized EM incidences from 8.1-12.5 GHz while satisfies the requirements of 1-bit coding without changing the polarization. Two types of multi-layer coding particles with different geometrical parameters are adopted to represent the digital states "0" and "1", which are easily promoted to terahertz and optics through modifying the size scale. To verify the ability to manipulate the EM waves, we first adopt the coding metasurface to achieve broadband beam forming by converting spherical waves to plane waves and realize high-directivity pencil beam in far field with low side lobes. We further arrange the particles according to the coding sequence 010101… to steer two symmetrical beams in different directions controlled by frequencies with the maximum range of the scanning angle of 30°-50.5°. The good agreements between the simulated and measured results validate the proposed broadband coding metasurface, indicating its huge potential in communication and radar imaging systems.