Phase gradient metasurface with broadband anomalous reflection based on cross-shaped units

It has been pointed out by many documents that a phase gradient metasurface with wideband characteristics can be designed by the unit with a low-quality factor (Q value). In this paper, a cross-shaped unit with a low-quality factor Q is proposed. By changing the variable parameters of the unit, it is found that the reflection phase of the unit can achieve a stable distribution of phase gradient in the frequency range of 8.0-20.0 GHz. we analyze variation of the electromagnetic field distribution on the unit with frequency and find that the size along electrical field polarization of electromagnetic field distribution area changes with frequency. Based on our design, effective size of electromagnetic field distribution area keeps meeting the subwavelength condition, thus stable phase distribution is gained across broadened bandwidth. It is found by the analysis of the phase gradient metasurface composed of seven units that the metasurface can exhibit anomalous reflection in the wide frequency band of 8.0-20.0 GHz, and the efficiency of abnormal reflection is higher in the range of 10.0-18.0 GHz. The error between the simulation results of abnormal reflection angle and the theoretical result is only - 1.5 degrees to 0.5 degrees after the work of comparison. Therefore, the metasurface designed by the new cross-shaped unit has a good control on the deflection direction of the reflected wave, and shows obvious advantages in widening the bandwidth.