Optically Transparent Microwave Metamaterial Absorber (OTMMA) is of significant use in both civil and military field. In this paper, equivalent circuit model is adopted as springboard to navigate the design of OTMMA. The physical model and absorption mechanisms of ideal lightweight ultrathin OTMMA are comprehensively researched. Both the theoretical value of equivalent resistance and the quantitative relation between the equivalent inductance and equivalent capacitance are derived for design. Frequency-dependent characteristics of theoretical equivalent resistance are also investigated. Based on these theoretical works, an effective and controllable design approach is proposed. To validate the approach, a wideband OTMMA is designed, fabricated, analyzed and tested. The results reveal that high absorption more than 90% can be achieved in the whole 6~18 GHz band. The fabricated OTMMA also has an optical transparency up to 78% at 600 nm and is much thinner and lighter than its counterparts.

This paper presents an ultracompact design of biomedical implantable devices with integrated wireless power transfer (WPT) and RF transmission capabilities for implantable medical applications. By reusing the spiral coil in an implantable device, both RF transmission and WPT are realized without the performance degradation of both functions in ultracompact size. The complete theory of WPT based on magnetic resonant coupling is discussed and the design methodology of an integrated structure is presented in detail, which can guide the design effectively. A system with an external power transmitter and implantable structure is fabricated to validate the proposed approach. The experimental results show that the implantable structure can receive power wirelessly at 39.86 MHz with power transfer efficiency of 47.2% and can also simultaneously radiate at 2.45 GHz with an impedance bandwidth of 10.8% and a gain of −15.71 dBi in the desired direction. Furthermore, sensitivity analyses are carried out with the help of experiment and simulation. The results reveal that the system has strong tolerance to the nonideal conditions. Additionally, the specific absorption rate distribution is evaluated in the light of strict IEEE standards. The results reveal that the implantable structure can receive up to 115 mW power from an external transmitter and radiate 6.4 dB·m of power safely.

Compensation circuits, the unavoidable components of the traditional inductive power transfer (IPT) systems for high efficiency, not only increase the circuit complexity, but also reduce the system reliability. Self-resonant coils are promising in capacitorless IPT systems. A high-efficiency novel Antisymmetric Planar Coil (APC) is proposed to improve the performance of self-resonant coils. The APC consists of two antisymmetric planar windings that are arranged in two parallel layers, and exhibits an intrinsic parasitic series capacitor. Possessing the simplest configuration, the APCs IPT system is only composed of two APCs, an AC source and a load. Based on analysis and simulations, the design guidelines for developing transmitting and receiving APCs according to the maximum power transfer principle and the maximum energy efficiency principle with given voltage transfer ratio are derived, respectively. The novel APC, the corresponding compact IPT system and the design guidelines are validated by design examples with experimental tests and a demonstration. Avoiding the compensation circuits, the APCs IPT system has compact configuration, high reliability, and proves to be a good candidate in wireless power transfer applications.

A novel coil with alternative clockwise and counterclockwise winding has been proposed and employed to construct Inductive Power Transfer (IPT) systems. After establishing the equivalent circuit of the proposed IPT system, the coil-to-coil, source-to-load and optimum transfer efficiency are analyzed mathematically. Then, Comprehensive expressions for accurate estimation of transfer efficiency of a realizable structure are deduced. Theoretical analyses indicate that it is not always mandatory to use extremely low-loss material to fabricate the coils for high-efficiency mid-range Wireless Power Transfer (WPT) systems. To validate the proposed IPT system, a prototype is designed, fabricated and measured. Good agreements are achieved between calculated and experimental results. It is demonstrated that the adoption of the present coil can enhance the IPT systems' performance significantly. Compared with traditional IPT systems, the present system can operate properly without surplus and complex compensating networks. Further, An IPT system at 13.56 MHz employing proposed coils without any matching networks is designed, fabricated and tested. This system is then used to drive a LED monitor wirelessly to demonstrate the feasibility of proposed system in commercial applications. Owing to its design simplicity and demonstrated benefits, the proposed configuration endeavors to replace traditional approach to design high-efficiency optimized WPT systems.

Electric vehicles (EV) have the potential to reduce greenhouse gas emissions, improve air quality, and lower mobility costs, thus promoting sustainable mobility. Battery management is crucial in electric vehicles to ensure safety, maximize battery lifespan, maintain optimal performance, and improve energy efficiency. However, the complex wiring harnesses required to transport sensor data make a Battery Management System (BMS) a complex and vulnerable block in EV design. This is due to weight and cost associated with extensive wiring harnesses, high connection failures probability, challenging maintenance, and limited flexibility in battery pack configuration. Researchers and manufacturers envisage a potential solution in Wireless BMS (wBMS) to improve EV safety, reduce weight, improve scalability, and enhance reliability by eliminating complex wiring. The state-of-the-art wBMS use wireless sensors, that themselves require a battery to operate, therefore, posing an additional liability and failure threat. Luckily, energy autonomous wireless sensors can be cutting-edge technology to irradicate this vulnerability and give the wBMS designers and manufacturers with the huge flexibility to further enhance reliability, reduce maintenance, lower weight, and improve environmental sustainability by eliminating the need for sensor battery replacements. This survey intends to summarize the recent contributions and developments made in providing the solutions for wBMS in automotive applications. A comprehensive review and analysis of power consumption of common communication standards used in wBMS is also provided. The potential of battery-free RFID (UHF/NFC) sensors in realizing energy autonomous wBMS for electric vehicles has been unearthed, several use cases, commercially available solutions and their practical application in automotive industry have been discussed. Moreover, this review serves as a useful guide for industry professionals and researchers developing battery-free passive wBMS, covering current advancements in battery-free passive wireless sensor technology, technology readiness, real-world operational challenges, and future trends.