This paper deals with the numerical evaluation of the magnetic field emitted by a wireless power system (WPT) in an electric vehicle (EV). The numerical investigation is carried out using a finite element method (FEM) code with a transition boundary condition (TBC) to model conductive materials. First, the TBC has been validated by comparison with the exact solution in simple computational domains with conductive panels at frequencies used in WPT automotive. Then, the FEM with TBC has been used to predict the field in an electric car assuming the chassis made by three different materials: steel, aluminum, and fiber composite. The magnetic field source is given by a WPT system with 7.7 kW power level operating at frequencies of 85 or 150 kHz. The calculated magnetic field has been compared with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) reference level demonstrating compliance for an EV with metallic (steel or aluminum) chassis. On the contrary, a fiber composite chassis is much more penetrable by magnetic fields and the reference level is exceeded.

As battery capacities become suitable for the mass market, there is an increasing demand on technologies to charge electric vehicles. Wireless charging is regarded as the most promising technique for automatic and convenient charging. Especially in publicly accessible parking spaces, foreign objects are able to enter the large air gap between the charging coils easily. Since the evoked magnetic field does not meet regulations, wireless charging systems are demanded to take further precautions related to the protection of endangered objects. Thus, additional sensors are required to protect primarily living objects by preventing them from being exposed to the magnetic field. In this paper, we propose a new approach for monitoring the air gap under the vehicle underbody using an automotive radar sensor on the vehicle side. The concept feasibility is evaluated with the help of a prototypical implementation. Further, two-dimensional signal processing techniques are applied to meet the requirements of inductive charging systems. Consequently, this paper provides measurement data for relevant use cases frequently discussed in the community of inductive charging.

This paper presents a resonant inductive link for power and data transfer to a pulse generator implanted in the chest. The proposed link consists of two planar resonators and has been optimized for operating in the MedRadio band centered at 403 MHz. The wireless power/data link occurs between an external resonator operating in direct contact with the skin and a receiving resonator integrated in the silicone header of a pulse generator implanted in the chest. Numerical and experimental results are presented and discussed. From measurements performed by using minced pork to simulate the presence of human tissues, an efficiency of about 51% is demonstrated. The feasibility of using the proposed link for recharging the battery of the medical device in compliance with safety regulations is also verified and discussed.

This work proposes a tunable sidelobe reduction method based on a GaN active-antenna technique, in which the output radio frequency power is controlled by the DC drain voltage of the amplifiers. In this study, a 1 × 4 array of active antenna with GaN amplifiers is designed and fabricated. GaN amplifiers capable of up to 10 W-class power output are fabricated and arranged for a four-way active-array antenna. The fabricated single-stage GaN amplifier offers a maximum power-added efficiency of 59.6% and a maximum output power of 39.3 dBm. The maximum output power is decreased to 36.5 dBm upon decreasing the operating drain voltage from 55 to 35 V. In this study, a 4.5 dB sidelobe reduction is demonstrated in a 1 × 4 active antenna based on this output power difference for each amplifier.

We address transmission between array antennas in the Fresnel region, where there is a difference between the theoretical and actual transmission efficiencies. In particular, we focus on the effect of synthesis loss in the receiving antenna's power combiner circuit caused by amplitude and phase differences among the signals received by the elements. We designed 24 GHz array antennas and investigated the effect of synthesis loss on transmission efficiency via simulation. The synthesis loss was found to increase for smaller transmitting antenna sizes and larger receiving antenna sizes. In addition, to clarify the origin of the discrepancy between the theoretical and actual efficiency values and accurately estimate the efficiency, we defined four other loss factors and calculated them via simulation. Based on the results obtained, we propose an approximate equation for transmission efficiency in terms of synthesis loss and aperture efficiency. Finally, we calculate the efficiency with the effect of the loss factors included and confirm that the calculated and measured efficiencies are almost identical.

A terrestrial microwave power transmission system is considered as an effective method for collecting natural energy. In this system, frequency dependence of the refractive index and multipath propagation due to the ground surface poses problems. In the study, a single-frequency retrodirective system was proposed with a beam pilot signal using dual-mode dielectric resonator antenna elements. The results confirmed that the beam pilot signal radiated from the entire surface of the receiving antenna and accurately used the same propagation space as that of microwave power by beam propagation method simulation. A dual-mode dielectric resonator antenna was proposed as a common array antenna element for the beam pilot signal and microwave power. This involves a cross-shaped hemispherical dielectric resonator structure, and an isolation level exceeding 60 dB was experimentally measured between the orthogonal ports of the fabricated antenna. The dual-mode dielectric resonator antenna with an isolation exceeding 60 dB was successfully developed as an enabling device to realize a single-frequency retrodirective system with a beam pilot signal.

New small unmanned air vehicles designated as micro air vehicles (MAVs) are increasingly attractive for research, environmental observation, and commercial purposes. As described herein, the feasibility of a system for wireless power transmission via microwaves for MAVs was investigated. For its light weight and flexibility, a textile-based rectenna was proposed for microwave wireless power transmission of MAVs. To investigate bending effects on radiation performance, a microstrip patch antenna with a 5.8 GHz left-hand circular polarization was developed on a textile substrate. The antenna return loss, 20 dB, increased slightly with the antenna bending angle. An axial ratio <3 dB was maintained when the antenna bend angle was <30°. A rectification circuit was formed on the back side felt with sandwiched copper foil as a ground plate. Its weight per unit area was 0.08 g/m2, with maximum rectification efficiency of 58% with 100 Ω load at 63 mW input power. The average and maximum total transmission efficiency using the 5.8 GHz multiple rectenna with a 2.45 GHz retrodirective system were, respectively, 0.44 and 0.60%. The possibility and feasibility of microwave power transmission system using the textile-based rectenna were evaluated.

In this contribution, the authors perform the design and show the experimental results relative to a prototype of a combined wireless power transfer (WPT)–power line communications (PLC) system, in which the WPT channel is interfaced to a PLC environment to allow data transfer when the cabled connection is no longer available. The main rationale behind this idea stays in the fact that PLC communication is now a popular choice to enable communications, for instance, in smart grids and in home automation, while WPT devices start to be available in the market (i.e. for mobile phones) and soon they will be a reality also for higher power (i.e. vehicle battery charging). In particular, theoretical insights about the requirements of the system are given; a two coils system has been implemented and a measurement campaign, together with simulations, show that the system is of great potentiality and could be used in applications where both wireless power and data transfer are needed (such as vehicles battery charging), achieving maximum power transfer and good data rate in order to transmit high-speed signals.