In order to continuously power movable sensors, we present an autotracking continuous-wave time reversal (TR) wireless power transfer (ACTR-WPT) system of a novel low-profile planar transmitter. The new transmitter is designed with a radio-frequency (RF)–channel cascaded structure, which couples only a little energy of the amplified feeding signal of each radiating element to the following cascaded one. Such RF-channel cascaded transmitter makes the decrease or increase of the number of the radiating elements quite flexible. The transmitting circuits are highly integrated with a microstrip antenna for every radiating element, which benefits the planar transmitter with the profile of less than 3 mm and the weight of each radiating element of less than 40g. Meanwhile, we develop an autotracking algorithm for the ACTR-WPT system, which inherently depends on the adaptive focusing mechanism of the TR technique. With the newly developed autotracking algorithm, we successfully demonstrate the experiments of powering the devices arbitrarily moving within a range from 1m to 7 m and the angle from -45° to +45°. The received dc power ranges from 1mW to 250 mW. The demonstration results are exciting for applications in charging or powering the movable sensors of low power consumption within a mid-range region.

In order to address the issue of wireless communication signal blocking in the traditional cavity resonance wireless power transfer (CR WPT), a wall-meshed cavity resonator constructed of the meshed metallic walls is proposed together with an analytical design method. This cavity resonator can not only generate and confine the electromagnetic waves of natural resonant modes inside the cavity resonator, but also support wireless communications with outside. The wall-meshed cavity resonator is analytically designed by the known theoretical equations without time-consuming optimizations and verified by electromagnetic simulations and experiments. The results show that the proposed CR WPT system can achieve simultaneous wireless power transfer in the cavity and wireless communications with outside. The maximum power transfer efficiency is higher than 85%. The power transfer efficiency exceeds 60% within about 70% areas inside the wall-meshed cavity. For wireless communication signals passing through the wall-meshed cavity, the attenuation at 2.1 GHz (4G), 2.45 GHz (Wi-Fi), and 3.5 GHz (5G) is about 6.0, 5.1, and 3.8 dB, respectively. Additionally, the safety performance of the proposed CR WPT system is numerically investigated by the specific absorption rate analysis of a human torso model.

Uniform microwave field (UMF) has increasing applications in microwave industries and electromagnetic measurements. In this work, we propose an analytical method to synthesize UMFs based on the Fourier transform (FT) and time reversal (TR) technique. FT is used to analytically obtain the excitation amplitudes for the antenna elements of time reversal mirror (TRM). TR is applied to compensate for their excitation phases so that all the TR signals radiated from the TRM antennas arrive at the target zone without phase difference. TRM is an antenna array of each antenna element with the TR processing ability, which is designed for UMF generation. Thanks to the analytical property, the proposed method provides a new efficient way to achieve the UMFs. Full wave simulations demonstrate the validity and accuracy of this method. Some critical factors that may affect the 3-dB field width, phase deviation and amplitude ripples of the UMFs are studied.

In this paper, a highly integrated transmission- type approach is proposed to generate scanning quasi-nondiffractive beams using a source-integrated folded transmitarray antenna (FTA) based on metasurface (MS). The proposed approach achieves large-angle scanning of quasi-non-diffractive beams in two dimensions while significantly reducing the profile height of the launcher, which effectively mitigates the lack of compactness and integration in existing research approaches. As a validation, a circularly polarized (CP) scanning quasi-nondiffractive beam launcher in the Ku -band is designed, which consists of two rotatable chiral MSs and a planar patch feed integrated into the bottom reflector. The MSs are designed to provide perfect polarization selectivity for folding the beam propagation path, alongside accurately implementing the required phase shifting. The two nonlinear phase profiles with controllable depth of field and the spherical wave compensation of the integrated feed source are encoded onto the two MSs, respectively. The designed launcher with a profile as low as 2.5λ ₀ was modeled and fabricated. Dynamic scanning of quasi-non-diffractive beams, covering a 104° field of view and 360° azimuth within a specified depth-of-field area, can be achieved by rotating the two MSs simply. Good agreement between simulation and measurement results proves the effectiveness of the proposed strategy. The proposed launcher has great potential for near-field high-speed communication, wireless energy transfer, and detection applications, especially in space-constrained situations.