| Microwave Power Transmission(MPT)is an energy transmission technology that transmits electric energy from one place to another through microwave beams.This point-to-point energy transmission mode breaks through the limit of transmission lines and has a very broad application prospect in the fields of space solar energy transmission,remote energy supply for UAV,power supply for remote areas,mobile power supply for battlefield disaster areas,wireless charging for indoor equipment,etc.After decades of development,MPT has formed a relatively mature research system and achieved very rich research results.However,there are still many key technologies that need to be solved before it goes into practical application.MPT system can be divided into two parts:energy emission subsystem and energy reception subsystem.In this paper,the microwave power emission device based on the reflectarray antenna and the energy reception device based on the electromagnetic power collection metasurface are studied to solve the problems in the microwave wireless power transmission system.The specific contents are as follows:1.Based on the structure of multi-resonance,a novel reflectarray element is presented in this paper.It can achieve phase shift coverage more than 360°in broadband with good linearity,when the incident angle of electromagnetic wave is in 45°the phase shift curve is basically unchanged,reflection coefficient is more than-0.1d B,which is meets the design requirements of large aperture and high aperture efficiency of MPT transmission antenna.A 19×19 elements reflectarray antenna is designed,the simulation show that the Gain of antenna is 28.7d Bi,the first sidelobe level is-19.3d B,the half power beam width is 5.3°,the 1d B gain bandwidth reaches 20.8%,the 3d B gain bandwidth reaches 46.9%and the aperture efficiency achieves 62.1%.2.A 5.8GHz reflectarray antenna which can generate non-diffraction Bessel beams and realize beam direction control in near-field based on the holography method is presented in this paper.The sub-wavelength unit cell of the reflectarray antenna with high reflection coefficient can obtain an accurate phase distribution to improve the energy transmission efficiency.The metasurface of the reflectarray antenna is composed of43×43 unit cells can realize 10m non-diffraction range by simulation,the radiated power attenuation is less than 2d B.In addition,the Bessel beams deflection of 10°from+z direction is achieved,the radiated power attenuation is less than 4d B.3.A new design of a polarization-independent dual-band metasurface absorber which based on improved Minkowski fractal structure is proposed in this paper.It is design for wireless power transmission,the proposed metasurface absorber is composed of many sub-wavelength elements,by adjusting the structure of the elements,it has rotational symmetry,and multi-frequency resonance characteristics,the proposed metasurface absorber array can keep more than 87%harvested efficiency at 2.45GHz and 93%harvested efficiency at 5.8GHz for arbitrary polarization of incident electromagnetic wave,the working frequency of the proposed absorber can cover the main working frequency bands of the current microwave wireless energy transmission system.The proposed metasurface absorber which has the great advantage of subwavelength,polarization independent,high harvested efficiency,is suitable for wireless power transmission especially in ambient power harvesting and UAV remote power supply.4.The design idea of integrating the metasurface and the rectifier semiconductor is proposed,and on this basis,a polarization-independent dual-band electromagnetic power collection metasurface is designed.The unit structure layer of the metasurface consists of a ring structure based on Minkowski fractal,a rectangular branch extending outward,and a rectifier diode embedded in the branch.The rectangular branches of the metal patch layers of each unit are connected through filter inductors,so that the rectifier diode and the metasurface unit are integrated in the same plane.While reducing the structural complexity of the traditional rectifier antenna and solving the problem of DC energy convergence,it realizes the effective collection of electromagnetic power at the dual frequency points of 2.4GHz and 5.8GHz,and has good polarization insensitive characteristics,which can be applied to the field of MPT.5.Based on the Bessel Beam holographic reflectarray antenna and integrated metasurface absorber research proposed in this paper,practical verification work was carried out on the energy emission subsystem and energy reception subsystem.the maximum transmission distance of the Bessel Beam holographic reflectarray antenna is set to 3m,which is 27×27 reflective array units,after practical testing,the reflective array antenna forms a Bessel beam and has good energy focusing effect;The integrated metasurface absorber composed of 7×7 units,the effective energy receiving area is384.16cm~2.After practical testing,the integrated metasurface absorber has an RF-DC energy conversion efficiency of 29.23%at 2.3GHz and 40.27%at 5.8GHz. |
PDF Full Text Request