Design Of Waveguide Near Field Coupled Wireless Transmission System

In today’s society,the emerging wireless power transfer(WPT)has attracted lots of people’s attention.Unlike the traditional electricity delivery through wire grids,the wireless power transfer technology does not rely on the wire cables,and hence the power supply shows flexibility in some particular scenarios,where the stable cable connection is unavailable.As well,the wireless power transfer does not require the direct connection of conducting metals,which in principle helps the avoidance of the electric shock from those exposed power plugs.Due to the above reasons,WPT has the potential applications in various practical scenarios and has been a hot topic in today’s power supply technology,with considering its flexibility and high safety.In this thesis,we propose and design a wireless power transfer system based on the near field coupling between a couple of wavelength compression transmission lines,which act as either the power supplier and the receiver.The operation frequency of our design is chosen as 13.56 MHz.The proposed WPT system can realize efficient and stable wireless power transmission,when the receiver is located at arbitrary positions along the long-distanced power supplier,as expected theoretically.The constructed wireless power transmission system in our work is composed of two hardware parts,i.e.,the wireless coupling structure and the control and accessory circuits,which in detail are:Ⅰ: Wireless coupling structure.By consulting the transmission line theory,we propose the inductively loaded transmission line design,which is achieved by making the straight metallic wires into helix structures.By applying the quarter-wavelengthed transmission line,a resonant structure with supporting traveling wave coupling is obtained.And,by applying the standing wave distribution on a typical transmission line,we propose the dynamic coupling between a long transmission line and a quarter-wavelengthed resonator(a short transmission line).We show that in case there exists only one single receiving structure,the power supply is hardly stable.However,a dual receiver design of the coupling structure can complement each other and overcome the drawbacks,thus efficient and stable coupling efficiency(as well as power transfer)at arbitrary location can be rendered.The coupling efficiency of the proposed structures are simulated by the commercial CST-microwave studio.The simulated results show that the coupled transmission lines can support a transmission efficiency up to 90%.Ⅱ: the hardware circuits.The controlling part of the WPT system are composed by a13.56 MHz signal generator,a CMOS bias circuit for the power amplifier,a class E power amplifier and a DC power supply.We perform in-depth analysis on the class E power amplifiers,in order to give a theoretical estimation of the performance(such as efficiency)in the system tuning.Meanwhile,the commercial MATLAB is used to numerically evaluate the key parameters of our power amplifier in the design.The commercial Advance Design System(ADS)software is used to simulate and optimize the whole power amplifier,as well as give an accurate estimation of the efficiency of thepower amplifier under varied terminal loads.In the experiments,the whole wireless power transfer system is constructed,tuned and tested.The measured power transfer efficiency is shown around 50%,which is deeply suppressed due to the degraded power conversion efficiency of the class E power amplifier.Despite the fact that the power amplifier does not behave as an efficient component,the whole system works as expected in the experiments,which illustrates the validation of our new strategy of WPT.