Wei Song

This brief presents a dynamic impedance matcher (DIM) for high-power rectifier in microwave wireless power transmission (MWPT) to enhance microwave rectifier efficiency over wide ranges of input power and load. The DIM based on an isolated Sepic converter performs dynamic impedance matching with the maximum power point tracking (MPPT). One digital processor is used to control multiple DIMs simultaneously to reduce power consumption. The DIM is implemented by a microcontroller and analog circuits and applied to 2.45 GHz system-level verification. The experimental results show that the overall power conversion efficiency (PCE) of the rectifier with DIM can reach more than 60% for the input power of 30 -37 dBm and the load of 10 -4000 Y, where the efficiency of the isolated DIM reaches 91.7%. The input power range above 60% PCE of the rectifier is at least 3 times of that under the situation without DIM and 10 times for the load range as well.

In this paper, a metasurface antenna (MA) is designed for quasi nondiffraction beam size adjustment and microwave power transmission. A phase calculation expression is derived to generate different spot sizes of generated quasi nondiffraction beams. The result shows the metasurface antenna can make the electric field decay slower and apply to various polarization situations. At the same time, the measured result demonstrates that we can adjust the size of the beam by setting the parameters ( d ) of the derived expression. As for the microwave power transmission, the proposed MA can deliver energy further, and the maximum harvested power by the receiver can up to more than 13 times as much as without metasurface condition when the transmission power is 0 dBm.

We present a novel phase modulation method for generating two-dimensional Airy vortex beams carrying orbital angular momentum (OAM) modes in microwave bands. This approach enhances the focal field intensity of the non-diffracting Airy OAM beam while simultaneously suppressing divergence at a longer distance without compromising its nondiffractive property. By leveraging Fourier optics theory, we theoretically analyze the propagation behavior of EM waves and outline a detailed design procedure. To achieve superior performance, a dual-polarized metal-only Huygens metasurface is designed at 5.8 GHz, synthesizing the full range of impedances required to attain 360-degree phase coverage and high transmission amplitude (-2 dB). To demonstrate the feasibility of our approach, we fabricate an experimental prototype using laser engraving, a cost-effective technique suitable for extreme environments. Full-wave simulations and experimental measurements are conducted to validate the design and its performance.

In this letter, a broadband and wide-angle linear-to-circular polarization converter (LCPC) based on three-layer transmissive metasurface is proposed, to solve the problem of efficiency degradation caused by polarization mismatch in mobile microwave wireless power transmission (MWPT). The simulated results show that our proposed model has an axial ratio (AR) of less than 3 dB in the 4.24-6.24 GHz band (38.17% bandwidth) with a maximum insertion loss (IL) of 1.66 dB for normal incidence in both yz and xz plane. In addition, 50° incidence angle stability can also be achieved. To verify the feasibility, a sample with a total dimension of 300×300×5.105 mm ³ is fabricated. The measured results demonstrate that our LCPC combines the advantages of broadband, wide-angle, low-loss and low-profile. With this LCPC, the received power is verified to remain stable when the polarization angle of the receiving antenna changes.

In this paper, a phase expression is derived to calculate the compensation phase of each point on the metasurface (MS), which is then used to generate a focused beam with different elevation (θ) and azimuth (φ) angles. The simulation results show that the expression can achieve both 1D and 2D focused beam scanning. An MS with an expected beam direction of θ and φ both equal to 45∘ is fabricated using the derived phase expression and a designed phase control unit. The final measurement results indicate that the beam can be generated with minimal error in the desired direction. Furthermore, due to the focusing effect of the MS, more power is concentrated in the direction of beam propagation. When compared with the system without the MS, the harvested power by the receiver can be improved by at least 39.0% (η>39.0%) across all measured ranges, with a peak value of η reaching 53.0% when the system incorporates the proposed MS. This means that the designed MS can adjust the direction of the generated beam while concentrating power on the beam propagation path. The method proposed in this paper can be applied to the moving target power transmission application.

In this paper, an impedance-matching voltage regulator (IMVR) for high-power rectifier in microwave wireless power transmission (MWPT) is analyzed and fabricated, which is designed based on Zeta converter and Linear voltage regulator (LDO). System-level verification shows the proposed novel IMVR has potential application value for high-power MWPT system. Measurement results show that this design scheme realizes larger load range of constant voltage output and higher RF-DC power conversion efficiency (PCE) while improving the applicability and practicability of microwave rectifier. With an input power of 37 dBm, the maximum conversion efficiency of the rectifier with IMVR can reach up to 57.41%. Besides, with an input power of 38 dBm, the highest output DC power can reach up to 3.4 W, meeting the rated power of most small electronics. Compared with other similar schemes, the proposed rectifier with IMVR presents higher overall efficiency and adjustable regulated output 5 V / 12 V / 24 V. The IMVR can overcome the impedance sensitivity of the rectifier and realize the output of stable DC voltage required by most electronics.

In this work, an inkjet-printed and flexible zero-index metasurface for microwave power transmission(MPT) harvester is proposed and measured. The substrate and conductor are separately based on Polyimide and liquid metal EGaIn(Eutectic gallium indium alloy, in which the mass fraction of Ga and In are 75.5% and 24.5%, respectively). To accommodate the complex MPT application environment, such as the uneven surface of the receiving device and the movement of the harvesting target, the flexible energy harvester has received attention and research. However, in practical application, the condition of the harvester bending and the power oblique incidence will occur. Due to the decrease of the effective wave vector, the harvested power decreases. The designed zero-index metasurface can refract the obliquely incident energy wave so that the wave vector can pass through it and transmitted vertically to improve this situation. The experimental results show that at 5.8 GHz, the harvested power of the harvester with the zero-index metasurface is greatly improved when the incident angle increases and the bending degree increases.

In this letter, a novel impedance matcher (IM) is designed based on Zeta converter to overcome the shortcomings of other impedance matching methods and improve the load range in low resistances. System-level verification demonstrates that the novel IM has a potential application value for microwave wireless power transmission (MWPT) system. Measurement results show the maximum power conversion efficiency (PCE) of the novel rectifier with IM can reach 73% when the input power is 32 dBm. In addition, the proposed rectifier circuit with IM can operate with above 60% overall efficiency when the load varies from 0.01 to 10 $\text{k}\Omega $ (1:1000) as input power of 32 dBm. Compared with that without IM, the application of IM can increase the load range by at least 1100% when the rectifier efficiency is >50.7%. The measurement results demonstrate that the rectifier circuit has a better performance when connected to the novel IM.