Wideband Multiple Bessel Beams With Desired Directions and Energy Distribution Proportion Based on Time Reversal and Genetic Algorithm in Microwave

In this article, a simple synthesis technique for the versatile and flexible generation of multiple Bessel beams with desired directions and energy distribution proportion based on time reversal (TR) and genetic algorithm (GA) is provided. For example, three transmission metasurfaces (TMSs) are designed based on the proposed technique: 1) single Bessel beam along $z$ -axis direction; 2) dual Bessel beams with equal energy distribution proportion for $(\theta =30^{\circ }$ and $\varphi =45^{\circ }$ ), and $(\theta =-30^{\circ }$ and $\varphi =45^{\circ }$ ); and 3) dual Bessel beam with desired energy distribution proportion (1:0.8) for $(\theta =30^{\circ }$ and $\varphi =45^{\circ }$ ) and $(\theta =-30^{\circ }$ and $\varphi =45^{\circ }$ ). The TMSs with size $8.21\lambda _{0}\times 8.21 \lambda _{0}$ are formed by units with a three-metal layer, which can provide high transmission amplitude (>0.9) and 360° phase shift in a wide frequency band from 10 to 18 GHz. For validating the design technique, TMS (3) is fabricated and measured, and the simulated and measured results agree well. There are three innovations in this article: 1) flexible design technique based on TR and GA; 2) high-efficiency TMSs. The maximum Bessel beam conversion efficiency is 37%; and 3) wideband is 57.1%. The developed design technique can be used in designing high-efficiency TMSs in near-field application scenarios such as dense channel communication, high-resolution microwave imaging, near-field detection, efficient wireless energy transmission, medical hyperthermia, etc.