Two-dimensionally high AR performance beam scanning utilizing randomly-rotated single-PIN-diode elements for circularly-polarized programmable metasurface.

In this paper, we introduce a novel technique that utilizes randomly rotated elements (RREs) for the cross-polarization and axial ratio (AR) control of a circularly polarized programmable metasurface (CPPMS). We evaluate the CPPMS performance by comparing RREs layout with uniform elements (UEs) layout, and analyze far-field radiation parameters for 50 groups of CPPMS with different RREs layouts. Simulation results demonstrate consistent and improved performance across various RREs layouts, showcasing reduced cross-polarization and enhanced AR beamwidth. To validate these findings, we design a 1-bit CPPMS in Ku-band comprising 20 × 20 elements with the optimal RREs layout, and conduct measurements in an anechoic chamber. The CPPMS prototype achieves high gain (22.34 dBi), low cross-polarization (-20.5 dB), and a narrow 3 dB AR beamwidth (8.93°). Notably, it offers wide-angle beam scanning capabilities of up to ±60°. The gain bandwidth at -3 dB ranges from 14.54 to 16.65 GHz, with a relative bandwidth of 7.3%, while the 3 dB AR bandwidth extends from 14.24 to 16.07 GHz. Consequently, the proposed 1-bit CPPMS exhibits high-performance two-dimensional AR beam scanning, presenting promising applications in satellite communications.

Tailless Information-Energy Metasurface.

Programmable metasurface technology can achieve flexible manipulations of electromagnetic waves in real time by adjusting the surface structure and material properties and has shown extraordinary potential in many fields such as wireless communications and the Internet of Things. However, most of the programmable metasurfaces have a common feature: a tail (electrical wires and DC powers), which is difficult to supply in some particular application scenarios such as canyons and mountains. To eliminate the limitation of DC power supply, the programmable metasurface and wireless power transfer technology are combined to propose a tailless information-energy metasurface (IEMS). The tailless IEMS platform can dynamically control electromagnetic waves without relying on an external DC power supply; instead, the required DC power is provided internally by the IEMS platform itself. In the tailless IEMS experiments, the concept is demonstrated through the dynamic regulation of wireless channels and the wireless transmission of DC power. This work provides a self-powered method for programmable metasurfaces, expands the application scenarios, facilitates the miniaturization of systems, and makes it easy to integrate with other systems.

The Efficiency Improvement of Multiple Receivers in Wireless Power Transmission by Integrating Metasurfaces.

In this paper, we propose the use of metasurfaces to enhance evanescent wave coupling to improve the wireless power transfer (WPT) efficiency of multiple receivers. A 4 × 4 negative permeability metasurface is designed and placed between the transmitter (Tx) and receiver (Rx) coils for the greatest improvement in transfer efficiency. Through the analysis of the number and position topologies of Rx coils, the efficiency can be greatly improved; the maximum efficiency at longer transmission distances is achieved through the 4 × 4 negative permeability metasurface in the multiple-receiver system. We show with simulation and measurement results that the power transfer efficiency of the system can be improved significantly by integrating metasurfaces. The maximum transfer efficiency is achieved in a multiple-receiver WPT system when the number and topology of Rx coils is case 0 of single transmitter-three receivers (STTR). The results show that the total efficiency of the multiple receivers WPT system can be as high as 97%.

Design and prototyping of highly-collimated long-distance optical systems with an LED light source.

Electrical lighting design is usually based on the illumination design. Its main task is to ensure that the electricity and optical system can be normal, safe, reliable, and economically viable. In this paper, we propose a design and optimization method for outdoor illumination systems to generate relatively powerful light beams for far distances. The illumination systems are based on highly integrated LED modules instead of high intensity discharge lamps. The size of the LED light-emitting surface is 2.5mm×2.1mm, and the secondary optical elements are composed of a basic plano-convex lens and a Fresnel lens. The results of simulation demonstrate that the emission angle of the system is 1.1°, and the central illumination at 2500 m away is more than 1 lx. The total system is simple but practical, and several groups can be combined into a larger system. Two proof-of-concept prototypes producing acceptable illuminance are developed, and one is composed of four groups whose light is visible from 5000 m away. Both are fully waterproof and in a high degree of protection. The systems can provide up to 12 h of continuous lighting, and the operating temperature rise is less than 25°C. The results indicate that our design can be applicable for practical wild working sites.