Abstract
We propose and implement a novel 1-bit coding metasurface that is capable of focusing and steering beam for enhancing power transfer efficiency of the electromagnetic (EM) wave-based wireless power transfer systems. The proposed metasurface comprises 16 × 16 unit cells which are designed with a fractal structure and the operating frequency of 5.8 GHz. One PIN diode is incorporated within each unit cell and enables two states with 180 ° phase change of the reflected signal at the unit cell. The two states of the unit cell correspond to the ON and OFF states of the PIN diode or “0” and “1” coding in the metasurface. By appropriately handling the ON/OFF states of the coding metasurface, we can control the reflected EM wave impinged on the metasurface. To verify the working ability of the coding metasurface, a prototype metasurface with a control board has been fabricated and measured. The results showed that the coding metasurface is capable of focusing beam to desired direction. For practical scenarios, we propose an adaptive optimal phase control scheme for focusing the beam to a mobile target. Furthermore, we prove that the proposed adaptive optimal phase control scheme outperforms the random phase control and beam synthesis schemes.
Highlights
In the last decade, due to the increasing number of wireless and mobile devices being used, charging these devices has become a crucial problem, which is capturing massive attention.The traditional charging method with cords is not preferable for futuristic systems and devices (e.g., Internet of Things, wireless sensor networks (WSN))
We considered a coding metasurface with M × N 1-bit unit cells as shown in as incident with an EM wave, the unit cell can operate in two states with the same reflected magnitude but 180◦ phase change
To enable the beam focusing ability, the control board plays a crucial role in coding metasurface, which provides an exact voltage to turn the PIN diode in each unit cell ON and OFF
Summary
Due to the increasing number of wireless and mobile devices being used, charging these devices has become a crucial problem, which is capturing massive attention. The authors first designed and fabricated 10 × 10 array to demonstrate the working ability of the unit cell and metasurface [8,9]. There has been an increasing number of research works which focus on using metasurface in wireless power transfer [16,17,18,19,20,21,22] These works are just able to do fixed focusing and are definitely inapplicable for mobile devices. The proposed metasurface consists of 16 × 16 unit cells which are designed to operate at 5.8 GHz with two states (ON/OFF states) corresponding to a 0◦ or 180◦ phase shift of the reflected signal. The experimental results showed that the optimal phase control scheme performs better than the random phase control and beam synthesis schemes
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