This paper presents a compact and ultra-wideband high-efficiency microwave rectifier for wireless power transmission (WPT) applications. The input-matching-network utilizes a compact asymmetric coupled transmission line structure, contributing to wideband performance. The rectifier adopts a voltage-doubler topology, resulting in a smooth input impedance across a wide bandwidth. The working principle of the asymmetric coupled transmission line matching network is analyzed. Simulation and measurement are conducted on the proposed rectifier. The fabricated prototype demonstrates a wide bandwidth of 162.5% (0.3–2.9 GHz with the power conversion efficiency (PCE) exceeding 60% at an input power of 18 dBm. Even at an input power of 10 dBm, the measured PCE remains above 50% over the working band. The proposed ultra-wideband rectifier shows promising potential for WPT applications including wireless powering of low-power electronic devices and sensors.

In this paper, a novel miniaturized implantable circular antenna is presented. It supports both wireless information communication and wireless energy transmission at the Medical Device Radiocommunication band (MedRadio 402–405 MHz) and the industrial, scientific, and medical bands (ISM 902.8–928 MHz). The antenna is circular to avoid sharp edges while miniaturization is achieved by adding two circular slots to the patch. The main scenario includes embedding into the muscle layer of a cylindrical three-layer model of a human arm for which several parameters are analyzed (resonance, radiation pattern, and specific absorption rate). Power transmission efficiency and interaction distance limits to ensure connections are also evaluated. Finally, the design is validated by an experimental measurement in an anechoic chamber, and some new improvements are proposed.

In this paper, a complete wireless power transmission scenario is presented, including an external transmission antenna, an in-body embedded antenna, a rectifying circuit, and a powered sensor. This system operates at the Industrial, Scientific, and Medical bands (902.8–928 MHz). For the antenna design, important parameters including reflection coefficient, radiation pattern, and specific absorption rate are presented. As for the rectifying circuit, a precise model is created utilizing off-the-shelf components. Several circuit models and components are examined in order to obtain optimum results. Finally, this work is evaluated against various sensors' power needs found in literature.

This paper focuses on non-radiative wireless power transfer implemented by means of a resonant magnetic coupling. The case of one transmitter and two receivers is considered and a rigorous analytical procedure is developed demonstrating that maximum power transfer or maximum efficiency can be achieved by appropriately selecting the load values. Both cases of coupled and uncoupled receivers are solved; closed formulas are derived for the optimal loads, which maximize either power or efficiency. It is shown that the resistances that realize maximum power transfer are always greater than the resistances that realize maximum efficiency. According to this observation, an optimal range of operation for the load resistances is also determined. Furthermore, it is demonstrated that in the case where the receivers are coupled the introduction of appropriate compensating reactances allows retrieving the same results corresponding to the uncoupled case both for powers and efficiency. Theoretical data are validated by comparisons with numerical results.

A novel wireless sensor network system with compatibility of microwave power transmission (MPT) using a Gallium Nitride (GaN) power amplifier has been fabricated and tested. The sensor node operates using electrical power supplied by the MPT system. Time- and frequency-division operations are proposed for the compatibility. Under the frequency-division operation, receiving signal strength indicator of −85 dBm and packet error rate of <1% were measured when the available DC power of a rectifier with 160 mW output power. Under 120-min measurement, sustainable power balance between radio-frequency–DC conversion and power consumption in stable operation of the sensor node was achieved.