Wireless Power Transfer And Energy Harvesting Technologies Based On Metasurfaces

Since the establishment of the concept of artificial electromagnetic metasurfaces(MS),many have made a lot of breakthrough progress in theoretical research,structural design,practical applications and so on.At present,it is also a cross fusion of optics,microwave,materials science,biology,system science etc.,and it is developing towards self-adaptation,digitalization and intelligence.Wireless Power Transfer(WPT)and ambient energy harvesting(AEH),on the other hand,as a revolutionary technology of the power supply,involving a very wide range of applications,including smart equipment,wireless sensors network,internet of things,the antenna engineering,material engineering,transport safety,EMC,market development,etc.,are gradually developed from theory to industrialization and commercialization.Metasurfaces have played an important role in wireless power transfer and ambient energy harvesting applications,and have generated many new concepts,designs,and applications,opening up infinite possibilities for many scientific research and engineering applications.This dissertation mainly studies new theories,methods and designs of wireless power transfer and ambient energy harvesting based on metasurfaces.The specific research contents are as follows:1.Based on the research of the MS energy harvesting structure,the mechanism of regulating electromagnetic wave by MS is analyzed,and the general design method of the MS energy harvesting structure is given.Two kinds of single-mode resonant metasurface energy collectors based on ring structure and complementary structure are proposed.Then four kinds of multi-mode resonant energy collectors based on fractal structure,double ring structure,nested ring structure and butterfly type structure are proposed.The innovative structural design of the MS collector makes use of the strong resonance and the highefficiency characteristics of the MS.The energy collector based on MS can maintain more than 80% energy harvesting efficiency in the corresponding operating band of resonance mode,and supports in a wide-range and multi-polarization,and has the characteristics of miniaturization.Compared with the antenna of the same size,it shows better efficiency than the antenna.Through theoretical analysis,simulation and experiment,the effectiveness of MS in wireless power transfer and energy harvesting are verified.2.To integrate the structure of the system and efficiently harvesting energy and convert it to DC,a variety of application modes of the MS energy harvesting structure are explored,and a new concept and method of the rectifying metasurfaces are proposed by integrating the metasurface structure with rectifying diodes and their circuits.Two rectifying metasurfaces based on a mushroom structure and a photonic bandgap structure are designed.Through theoretical analysis,simulation,and experimental tests,it is verified that the rectified metasurface can maintain high energy harvesting efficiency over a wide input power range,and has the characteristics of adjustable and self-adaptive input power without changing the topology and parameters.It has the advantages of multi-mode resonance,wide-angle,polarization-insensitive,and miniaturization.3.By using the concept and design idea of the rectifying metasurface,the rectifying metasurface antenna for simultaneous wireless information and energy transmission system is studied.We propose two kinds of the innovative design of the rectifying metasurface receiving antenna for simultaneous wireless information and energy transfer.One is the coaxial feeding microstrip antenna,and the other is the aperture coupling antenna.The two antennas are analyzed,simulated and tested.It is verified that the metasurface can not only improve the performance of the antenna but also rectify and output DC power while the antenna receives RF energy.Experiments on simultaneous information and energy transmission are carried out.The metasurface structure is used to enhance antenna performance while capturing energy flow.It is verified that the two proposed rectifying metasurface antennas could receive energy and information simultaneously.Further,by changing the number of metasurface structures loaded on two different types of antennas,the energy flow and information flow can also be allocated power in the time domain or the frequency domain according to the demand,thereby achieving the self-adaptive reception trade-off of energy and information.4.The space,time,and frequency domain distribution characteristics of the electromagnetic radio frequency(RF)power spectrums in the practical environment are tested.The results show that the current electromagnetic wave spectrums in the actual environment are mainly distributed in TV broadcasting,wireless communication bands,Wi Fi bands,and so on.The distribution density is closely related to the time,space and the distance between the transmitting sources,but the overall difference is not significant.This test provides data support for the research and design of wireless power transfer and ambient RF energy harvesting system solutions suitable for practical scenarios.5.A point-to-point metasurface-based wireless power transfer system consisting of near-field focused metasurface array and metasurface harvester is proposed,and a systematic experiment of wireless power transfer is carried out.The system has a high transfer efficiency of 70%.Then,an indoor metasurface-based ambient RF energy harvesting system composed of a metasurface array harvester,a rectifying circuit and an energy management circuit is proposed,and the system experiment is carried out.The experiment shows that the metasurface-based system can harvest the Wi Fi energy in the environment to charge the supercapacitor and drive the sensor in order.The role and advantages of metasurfaces in wireless power transfer and ambient RF energy harvesting systems are verified.