Search

The rapid and efficient design strategy represents a highly intriguing research domain within the realm of metasurfaces. It necessitates minimizing the data load in coding metasurface design, facilitating the development of a precise approach to designing metasurfaces with specific characteristics. In this paper, we proposed a restrictive design strategy of metasurface for coding phase distributions based on the Fibonacci sequences, which is efficient to optimize designated radar cross section (RCS) reduction according to application requirements. Through the given restrictive strategy, the encoding range of the metasurfaces is reduced from the entire metasurfaces to the initial phase units in the corners, greatly reducing the total amount of data in the optimization database. In order to verify the availability of the strategy, RCS reduction metasurfaces with variable phase sequences in microwave region are analyzed. For broadband and wide-angle RCS reduction, the optimized Fibonacci discrete phase gradient (FDPG) metasurface is obtained by adjusting the phase sequences. Both the simulation and measured results show that the optimized FDPG metasurfaces by the proposed designing strategy have the RCS reduction of −10 dB in the frequency ranges of 6 GHz to 18 GHz under wide incidence angles from 0° to 30°. The simulated and measured results are good consistent over the whole frequency ranges and angle regions. This method combines mathematical sequences with physics organically, making it an important field in metasurfaces research and it is expected to play an important role in future studies.

A broadband radar cross-section (RCS) reduction employed by the vortex metasurface is proposed. The underlying physics is associated with the Pancharatnam-Berry geometrical phases involved in spin-to-orbital angular momentum conversion. The proposed metasurface generates spin-controlled vortex waves with different topological charges. The vortex singularity implements specular extremely low RCS reduction. The prototypes are fabricated and measured to verify the wideband performance of the RCS reduction. The simulated results illustrate that −10 dB broadband RCS reduction from 9 GHz to 22.5 GHz and the RCS reduction has peak values −37.2 dB, −40.8 dB, and −42.5 dB at 9.8 GHz, 13.1 GHz, and 20.8 GHz, respectively. The measurement results illustrate that −10 dB RCS reduction over 9.1–18 GHz is realized, and the RCS reduction peak −53 dB at 10.1 GHz. The measured electric field intensities and phase distribution of the vortex metasurface also be displayed. Due to the limitation of experimental conditions, no test was done in the range greater than 18 GHz. Far-field results achieve good agreement between simulations and experiments, and the near-field measurements are a subtle difference in the experimental results. This work reveals the potential advantages of vortex waves in the fields of multifunctional electromagnetic stealth, beamforming for communication systems, etc.