Research On The Theory And Key Technologies Of Focused Electromagnetic Metasurface Wireless Power Transfer

In recent years,wireless power transfer(WPT)technology has gradually entered people’s field of vision.WPT technology has been commercialized,especially in the fields of smart terminals,internet of things,human body local area networks,smart home devices and industrial electric vehicles.However,with the continuous development of WPT technology,people have also put forward higher and higher demands on the efficiency and distance of wireless power transfer.Electromagnetic metasurface is a new method that can flexibly regulate the phase,amplitude and polarization of electromagnetic waves.Its development has brought about many new concepts and potential applications.This thesis takes electromagnetic metasurface and wireless power transfer as the starting point.It mainly studies the use of reflective metasurface to realize the focused transmission of wireless energy,and at the same time studies the conversion of microwave energy,including the design and matching of RF rectifier circuits,which is aimed at establishing an efficient microwave wireless power transfer program depending on focused reflective metasurface.In addition,this thesis also studies the use of reflective metasurface to solve the problem of blind area coverage of future communication systems.The specific research work in this thesis includes the following aspects:1.Design of near-field focusing based on reflective metasurface.The theoretical analysis and design of the focused metasurface with different number of feed points and focal points were carried out,including single feed and single focus,single feed and dual focus,dual feed and single focus,dual feed and dual focus.A focused metasurface with independent control of the polarization focus is designed.When the polarization of the feed changes,focus position generated by the metasurface changes accordingly.A new design idea is highlighted,namely the design of multi-focal unequal power distribution,which makes the energy distribution at the focus position adjustable.Two focused reflective metasurface working at 10 GHz with a size of 390 mm×390 mm were processed.The experimental results show that this design achieves a good function of wireless power diversity and can independently control different polarization focus and adjust focus power distribution.2.Research and design of RF rectifier circuits.The design of rectifier circuits with different input power and working frequency is discussed.A rectifier circuit working at 2.45 GHz for low input power is designed.A matching network loaded with high-order harmonic suppression microstrip is used to concentrate the RF energy in the rectifier diode section.The experimental results show that 28% rectification efficiency can be obtained when the input power is-20 d Bm,and 42% rectification efficiency can be obtained when the input power is-10 d Bm.We also designed a rectifier circuit working at 10 GHz,and the simulation efficiency can reach 67% when the input power is 5d Bm.3.Research on dual cross-dipole(DCD)reflective metasurface.A novel metasurface element based on double-layer cross structure is designed.The range of reflection phase can achieve more than 500° while the linearity of the phase shift curve is good.The element has good dual-polarization orthogonality and angle stability.A scaled 16×16 directional-beam reflective metasurface was designed with 1 d B directivity-bandwidth up to 20.7%.The numerical simulation software was used to simulate the directional-beam reflective metasurface coverage of the signal blind area.