Efficient and stable wireless power transfer based on the non-Hermitian physics

As one of the most attractive non-radiative power transfer mechanisms without cables,efficient magnetic resonance wireless power transfer(WPT)in the near field has been extensively developed in recent years,and promoted a variety of practical applications,such as mobile phones,medical implant devices and electric vehicles.However,the physical mechanism behind some key limitations of the resonance WPT,such as frequency splitting and size-dependent efficiency,is not very clear under the widely used circuit model.Here,we review the recently developed efficient and stable resonance WPT based on non-Hermitian physics,which starts from a completely different avenue(utilizing loss and gain)to introduce novel functionalities to the resonance WPT.From the perspective of non-Hermitian photonics,the coherent and incoherent effects compete and coexist in the WPT system,and the weak stable of energy transfer mainly comes from the broken phase associated with the phase transition of parity-time symmetry.Based on this basic physical framework,some optimization schemes are proposed,including using nonlinear effect,using bound states in the continuum,or resorting to the system with high-order parity-time symmetry.Moreover,the combination of non-Hermitian physics and topological photonics in multi-coil system also provides a versatile platform for long-range robust WPT with topological protection.Therefore,the non-Hermitian physics can not only exactly predict the main results of current WPT systems,but also provide new ways to solve the difficulties of previous designs.     

非厄米物理启发的高效无线电能传输

无线电能传输技术是指不需要线缆或者波导结构,利用电磁波直接将电能从电源传输到负载的技术。作为能量传输的一种全新方式,无线电能传输技术可以极大地提高供电设备的安全性、可靠性和便捷性,其在消费电子行业、自动化工业车间以及人工智能平台等需要高自由度供能的场景中具有重要的应用价值。目前无线电能传输技术仍存在一定的局限性,特别是对于广为关注的磁共振耦合无线电能传输技术,面临着高效率和稳定性难以兼顾的巨大挑战。文章以近场无线电能传输技术为研究框架,深入介绍非厄米新物理在无线电能传输系统中的调控机理,及其在高效、稳定、待机功率损耗、电磁环境兼容等方面的突出优势,最后对无线电能传输未来的研究方向进行了展望。     

Wireless adiabatic power transfer

We propose a technique for efficient mid-range wireless power transfer between two coils, by adapting the process of adiabatic passage for a coherently driven two-state quantum system to the realm of wireless energy transfer. The proposed technique is shown to be robust to noise, resonant constraints, and other interferences that exist in the neighborhood of the coils.     

无线供能演示装置

根据电磁感应耦合原理,建立电容补偿式电路的相量模型,确定了影响传输效率的主要因素。基于实验得出最优电路参量,制作了简易的无线供电小车演示装置,具有较好的教学演示效果。     

无线携能通信系统中基于能量获取比例公平的波束成形设计

针对无线携能通信系统中存在能量获取不均衡的问题, 提出了一种基于能量获取比例公平的波束成形设计方案. 该方案在满足信息接收者的信干噪比以及发送端的最大发送功率等约束条件的基础上, 通过优化波束矢量实现能量获取的比例公平. 此设计在数学上是一个很难直接求解的非凸优化问题.为此, 本文首先利用半定松弛技术将其转换为半定规划问题, 然后结合二分法提出了可以获得最优波束矢量的迭代算法.此外, 在发送端仅知道部分信道状态信息且知道信道误差范围的情况下, 采用最差性能最优的方法对原优化问题进行了鲁棒波束成形设计, 并提出了相应的迭代算法. 仿真结果表明所提算法均可实现能量获取的比例公平且性能达到全局最优.     

Estimate of the maximum range achievable by non-radiating wireless power transfer or near-field communication systems

Models relating the coupling coefficient of coupled circuits to their physical layout and separation are essentially empirical in nature and have, until very recently, been available exclusively for inductive systems. In this work, we propose elementary models for representing the evolution, with distance, of the coupling coefficient between two dipoles arranged in different configurations. Both the electric and magnetic coupling cases are examined. We demonstrate that in the case of electrically coupled dipoles, with due consideration for specific practical constraints, the coupling coefficient is optimal when the dipoles are asymmetrical and arranged in an axial configuration. We show that the rate of fall of coupling coefficient increases with the relative separation between the dipoles. Finally, a simple formula for estimating the range of all non-radiating resonant power transport devices is proposed.     

Efficient weakly-radiative wireless energy transfer: An EIT-like approach

Inspired by a quantum interference phenomenon known in the atomic physics community as electromagnetically induced transparency (EIT), we propose an efficient weakly radiative wireless energy transfer scheme between two identical classical resonant objects, strongly coupled to an intermediate classical resonant object of substantially different properties, but with the same resonance frequency. The transfer mechanism essentially makes use of the adiabatic evolution of an instantaneous (so called “dark”) eigenstate of the coupled 3-object system. Our analysis is based on temporal coupled mode theory (CMT), and is general enough to be valid for various possible sorts of coupling, including the resonant inductive coupling on which witricity-type wireless energy transfer is based. We show that in certain parameter regimes of interest, this scheme can be more efficient, and/or less radiative than other, more conventional approaches. A concrete example of wireless energy transfer between capacitively-loaded metallic loops is illustrated at the beginning, as a motivation for the more general case. We also explore the performance of the currently proposed EIT-like scheme, in terms of improving efficiency and reducing radiation, as the relevant parameters of the system are varied.     

Time allocation improvement method for UAV-based wireless energy transfer cooperative mobile edge

Wireless power transfer (WPT) and mobile edge computing (MEC) are two advanced technologies that could improve the computing power and range of mobile devices. However, by integrating the unmanned aerial vehicle (UAV) into wireless powered MEC systems, wireless energy transfer will be susceptible to the “double near–far” effect. Therefore, in order to further overcome the influence of the “double near–far” effect, this paper considers the optimization of time slot allocation for UAV-assisted wireless powered cooperative MEC system, which includes an access point (UAV) and two mobile devices. The purpose of the study is to minimize the total transmission energy of the UAV while satisfying the delay and size of the computational tasks, so this paper proposed a 2:1:1 time-slot optimization allocation method. The method exploits the synergy of users so that the mobile device which is closer to the UAV acts as an offloading relay, by combining power and time slot optimization to minimize the total energy consumption of the UAV. Compared with the equal time slot scheme before the improvement, this method can not only utilize the wireless transmission energy to charge the mobile device for more time in the first period, but also can save the time of data transmission of the closer device in the third period, and it can enhance the rate of data transmission of the mobile devices at the same time. The results show that the task capacity of the system computed will be increased compared to the original scheme; the total transmission rate of the whole system is also improved by the same order of magnitude. The simulation results verify the effectiveness and reliability of the algorithm of the paper, and the comprehensive performance of the system can be maximized by the flexible offloading algorithm.     

基于环磁美特材料的无线传能系统

传统的四线圈磁共振耦合无线传能系统已在移动电子设备、电动汽车无线充电中得以应用,然而,其传能效率仍然因其磁场空间分布的发散性而难以提高.为了克服上述缺点,我们提出了一种基于环磁美特材料、磁场更为局域的高效无线传能系统.该系统将四线圈系统中的一对磁谐振耦合线圈替换为具有环磁谐振特性的四个非对称开口谐振环.该环磁模式具有高Q值、低金属损耗以及辐射抑制的特性.实验结果表明,相对于四线圈系统,该系统的磁场更为集中,能量传输效率更高.     

Long range inductive power transfer with superconducting oscillators

Resonant inductive power transfer has demonstrated the transfer of 60 W at distances in excess of 2 m with as much as 40% efficiency. The loss mechanisms include internal dissipation and radiated power. By constructing superconducting oscillators and operating at lower frequencies, both of these loss mechanisms are reduced, and this same power can be transferred at distances in excess of 100 m. A performance analysis of such a system is presented, along with proposed low-loss coil and capacitor designs to achieve this performance.     

An overview of simultaneous wireless information and power transfer in massive MIMO networks: A resource allocation perspective

Providing a stable and perpetual source of energy to charge battery-powered wireless communication devices is viewed as a major challenge in wireless communication systems. This challenge leads to the trending research area where radio frequency signals are being exploited for energy harvesting purposes. The technique for achieving this is known as simultaneous wireless information and power transfer (SWIPT). In recent studies on SWIPT, the massive Multiple-Input-Multiple-Output (MIMO) aided energy harvesting has attracted considerable attention from the research community. This can be attributed to the high energy delivery rate of massive MIMO antenna systems due to their capacity to focus transmitted signals in the direction of the intended receivers. However, SWIPT in massive MIMO networks requires an optimal design to achieve a proper balance between different conflicting network objectives. In this article, we aim to discuss various contributions to SWIPT in massive MIMO networks in order to address critical design issues. In particular, we focus on the widely adopted approach to resolving SWIPT-related issues in massive MIMO networks, that is, the resource allocation design. We also extend our discussion to studies dedicated to solving critical design challenges. In this regard, we take into consideration the energy efficiency and security aspect of the system design. Finally, we identify potential areas that can be explored for future research work.     

基于无线通讯技术脉搏检测仪的设计与实现

脉搏是反映人体生理健康状况最常见的重要生理现象,临床上有许多疾病,特别是心脏病都可使脉搏发生变化,因此脉搏信息检测与处理在临床医学具有十分重要的现实价值和意义。传统脉搏检测仪多以在线直测的方式检测,检测装置使用灵活度较低,不适用于普通家庭检测。针对此问题,对传统测量方法加以改进优化,提出了基于无线通讯技术的研究方案,方案以单片机为信号处理单元,以无线传输为控制核心,以ST188光电传感器为采集单元,同时结合nRF24l01无线传输模块,通过硬软件设计实现脉搏数据的采集与处理,以及无线发射、接收和脉搏数据的显示。实验表明,该脉搏检测仪具有检测数据准确、检测效率高等优点。同时,脉搏检测仪器精巧便于携带,而且成本较低,便于普通家庭使用。     

Relay selection and nonlinear energy harvesting in full-duplex multi-relay cooperative network

Energy harvesting (EH) is a promising technique to extend the lifetime energy-constrained devices in wireless networks. This paper analyses the significance of relay selection and non-linear EH in evaluating the performance of Full-duplex (FD) decode-and-forward (DF) multi-relay cooperative network. The relay selection is considered under three scenarios based on channel state information (CSI) availability. We compare the EH performance of a hybrid power-time-splitting (PTS)-based non-linear energy harvester with time-spitting (TS) and power-splitting (PS) EH at the relay node. We derive the expression of outage probability (OP) of FD DF multi-relay cooperative network over independent and identically distributed Rayleigh fading channels. Numerical results show that the outage performance of the system is significantly enhanced by deploying an ideal relay selection scheme. This paper also gives insights about the combined effect of saturation threshold of non-linear EH and residual self-interference (RSI) on the system performance. Unlike linear EH systems, the non-linear EH causes the outage floor even when the RSI is significantly small. The response of the system is also analysed for the impact of TS and PS ratios. Furthermore, we also investigate the system’s performance in terms of other system parameters like the number of relays and data transfer rate. Monte Carlo simulations are used to verify the analytical expressions.     

Several optimization problems in satellite optical communications: Models and solutions

In this paper, we address several optimization problems in satellite optical communications. We show that the inter-satellite links with swaying transmitters can be described as an equivalent fading model. We further indicate that the instantaneous signal-to-noise ratio follows the reciprocal Pareto distribution. Then we conduct the analysis on several performance metrics such as the first and second moments of signal-to-noise ratio, the amount of fading, as well as the outage probability. Based on these metrics, we establish optimization models and provide the corresponding solutions.     

AN-aided beamforming for IRS-assisted SWIPT systems

This paper studies artificial noise (AN)-aided beamforming design in an intelligent reflecting surface (IRS)-assisted system empowered by simultaneous wireless information and power transfer (SWIPT) technique. Multiple power splitting (PS) single-antenna receivers simultaneously receive information and energy from a multi-antenna base station (BS). Although all users are legitimate, in each transmission interval only one receiver is authorized to receive information and the others are only allowed to harvest power which are considered as unauthorized receivers (URs). To prevent information decoding by URs, AN signal is transmitted from the BS. We adopt a non-linear model for energy harvesting. In the optimization problem, we minimize the total transmit power, and for this purpose, we utilize an alternating optimization (AO) algorithm. For the non-convex rank-one constraint for IRS phase shifts, we utilize a sequential rank-one constraint relaxation (SROCR) algorithm. In addition to single antenna URs scenario, we investigate multi-antenna URs scenario and evaluate their performance. Simulation results validate the effectiveness of using IRS.     

Advanced modulation formats for delivery of heterogeneous wired and wireless access networks

It is believed that the integration of wired and wireless access networks (or heterogeneous network) will provide high bandwidth and flexibility for both fixed and mobile users in a single and cost-effective platform. Here, we propose and demonstrate a signal remodulated wired and wireless network with wireless signal broadcast. Dark-return-to-zero (DRZ) and polarization-shift-keying (PolSK) signals are used for the downstream wired and wireless applications respectively. At the remote antenna unit (RAU), the PolSK signal is demodulated to produce the binary-phase-shift-keying (BPSK) signal, which will be used for the wireless broadcast application. Signal remodulation is demonstrated using reflective semiconductor optical amplifier (RSOA) as a colorless reflective modulator in the optical networking unit (ONU)/RAU. The downstream signal is remodulated at the ONU/RAU to produce the non-return-to-zero (NRZ) upstream signal.     

Synthesis and microwave dielectric properties of an electronic ceramic Y2WO6 for wireless communications

Y₂WO₆ ceramics were fabricated via a solid-state reaction method and investigated structure stability, densification, microstructure, and dielectric properties at microwave frequency range. Y₂WO₆ crystallized in a monoclinic structure and stabilized to 1500 ^∘C, beyond which the decomposition of Y₆WO₁₂ occurred. Y₂WO₆ ceramic could be sintered into a compact bulk at 1450 ^∘C, which was characterized by a high relative density ∼ 97.6% and a dense microstructure. The favorable dielectric performances were achieved at 1450 ^∘C with a relative permittivity ${\epsilon }_r\sim 11.4$, a quality factor $Q\times f\sim 42,380$ GHz ($f=8.6$ GHz), and a temperature coefficient of resonant frequency ${\tau }_f\sim -49.0$ ppm/^∘C. The MW properties of Y₂WO₆ suggest that it could be useful candidate material for low-loss dielectric resonators.     

无线传感器网络中继节点布居算法的研究

本文表述的是在该应用背景下引入多约束条件, 并采用枚举法与贪婪寻优算法相结合的方法, 解决了在可以作为中继节点设置位置的预设中继节点位置集合内, 合理选择中继节点设置位置以及既存网络因添加新传感器节点所引起的中继节点追加的问题. 仿真实验表明, 本文提出的中继节点布居与追加优化算法能够保证多约束条件下网络的容错性. 同时提出的基于最小网络距离因子评价标准, 有效提高了中继节点布居算法的能效性.