Abstract:Wireless power transfer has recently become a hot research topic due to its potential wide applications in different areas such as implanted medical devices and personal electric devices.This paper presents a review of the progress in the area.Firstly,the backgrounds and basic theories of general wireless power transfer technologies are introduced.Then one of the technologies,the magnetically-coupled-resonant system,is presented and focused on.Properties of the magnetically-coupled-resonant system are described,including over-,critical-and under-couplings.Finally,challenges in developing and applying the magnetically-coupled resonant wireless power transfer systems are summarized.

Abstract:Monolithic microwave integrated circuit (MMIC) has played an important role in consumer and military applications.Among MMICs,high power amplifier is indispensable and the most complex component which enable transmitter delivers signal with sufficient power into free space.This paper provides chip designers a comprehensive design references and reviews the current development status of MMIC power amplifier basing on academic reports and commercial products datasheet.Firstly,various MMIC PA fabrication technologies classified as GaAs,GaN,CMOS and SiGe etc.are discussed.Then MMIC PA design techniques for satisfying specifications like high power output,broadband and high efficiency are introduced.Finally,paper concludes the processes and design techniques for MMIC power amplifier.

Abstract:MPT (Microwave Power Transmission) technology transfers power wirelessly from point to point by microwave beam,which could be applied in the solar power satellites,airships in the near space,and wireless sensors,etc.The rectenna,receiving the microwave power and converting it into the direct current power,is the key device of an MPT system.Firstly,the latest research development of rectennas is overviewed in terms of expending the operation frequency bands,the input power and the resistive load ranges.Secondly,the effective design methods of rectennas are outlined after analyzing the topological structures of the rectifying circuits and their corresponding application conditions,which are the core component of rectennas.Finally,the problems about rectennas to be solved in the future are analyzed and the research directions of MPT technology are proposed.

Abstract:Wireless power transfer (WPT) is a promising technology and has potential applications where the wired power transmission is inconvenient or impossible,such as wireless charging of sensors and power harvest of battery-free devices.In this paper,the research significance and working principle of the WPT are introduced.Then a research subject is put forward that the efficiency of the rectifier in the receiving terminal of the WPT system is sensitive to the input power.Subsequently,researches carried out to cope with this issue are discussed.Among them,three novel efficient methods are detailed in this paper,which use passive network to extend the input power range for high rectifying efficiency.Finally,the future research orientation of the microwave rectifier is discussed.

Abstract:Microwave power transmission (MPT) technology is one way to realize long-distance energy transmission.It is also the key technology of the space solar power system (SSPS).In this paper,the research status of microwave power transmission at home and abroad is introduced.The system composition and key technology of microwave power transmission are analyzed.The microwave transmitting subsystem and the microwave receiving subsystem are discussed in detail.Finally,the existing problems and the future development trend of microwave power transmission are summarized.

Abstract:Classification of underwater wireless power transfer (UWPT) is given first and then basic topology and operation principle of inductive UWPT are presented followed by its optimal operational frequency,transfer distance,choice of coil structure,eddy current loss and frequency splitting.Next,magnetic resonance UWPT and electrical coupling UWPT are described briefly.Finally the future challenges of UWPT are introduced.

Abstract:In recent years,metamaterial has broken physical limitations of traditional materials and structures,which would bring new development of high-efficiency transmitting antennas.It has got more and more attentions.In this paper,the research overview of the theory and structure of metamaterial have been introduced at first.Furthermore,the researches of several novel metamaterial technologies on improving the efficiency of planar antenna elements are specifically given and analyzed,including non-periodic metamaterial technology,metamaterial as novel radiation elements or low-profile reflection plane,etc.Finally,aiming at the requirement of wireless energy harvesting on high-efficiency antenna array,excitations using high-order modes and novel low-loss transmission lines have been introduced for low-loss feeding networks of antenna arrays and higher system efficiency.

Abstract:Medium-range wireless power transfer (WPT) can be realized in several different ways,e.g.by using inductive or capacitive coupling and resonant or non-resonant networks.This contribution focuses on a WPT link implemented by inductively coupled resonators.The case of a link using just two resonators (direct link) and operating at the main resonant frequency is investigated.It is shown that the operation at the main resonant frequency allows optimizing either efficiency or available power on the load,depending on the network parameterization.

Abstract:In this paper three different operative regimes for a resonant inductive Wireless Power Transfer link are discussed.The first operative regime provides a constant output voltage or current.The second analyzed operative regime adopts a frequency agile operative scheme and is well-suited for applications requiring a performance independent of the coupling coefficient.Finally,the third operating regime provides a load-independent output voltage or current.For all the analyzed cases the relevant equations are illustrated and discussed.Some experimental data are also reported for validation.

Abstract:In order to improve the efficiency of dual-band magnetic resonance wireless power transfer (WPT) system,this paper presents a pair of dual-band transmitter and receiver at Industrial Scientific and Medical (ISM) band.Firstly,the two different resonators of the transmitting end are fed by one feeding loop,which is the same as that of the receiving end.Power is transferred from the transmitter to the receiver at the operating frequency of the two resonators by magnetic resonance.Since the two resonators are both delivering power at their own resonant frequency,the efficiency of proposed WPT can reach impressive values at a relative long distance.A pair of prototype transmitter and receiver is implemented using printed circuit boards (PCB) to validate the advance of the proposed scheme.Simulation and measurement results illustrate that the two operating frequencies of the WPT are 6.78 MHz and 13.56 MHz.The power transfer efficiencies reach their maximum value of 88.5% and 56.7% respectively when the distance is 60% of the overall dimensions.

Abstract:Efficiency of rectenna is crucial to overall efficiency of far distance microwave power transmission.The mathematical description for rectenna efficiency is presented in this paper,and then the matching principles and methods are investigated on multiple interfaces of power beam incident,power transfer,power conversion and DC power combining.A design concept is developed based on multi-interface matching.Experiment is conducted with respect to the proposed matching principles,which verifies the analysis on wave impedance matching and input impedance matching.

Abstract:An ambient WiFi energy harvesting system is presented in this paper,with operating frequency from 2.4 GHz to 2.485 GHz.A voltage multiple rectifier is used in this design,and a broadband matching network for the circuit from antenna to rectifier is proposed to improve the efficiency of energy harvesting.S₁₁ of the proposed broadband matching circuit is less than -10 dB within the WiFi working frequency range.The harvesting signal can be increased by 4 times through the rectifier circuit,thus effectively improve the RF-DC conversion efficiency.Experiment results show that,with an input power of -10 dBm,the design achieves 40% of RF-DC conversion efficiency and the super capacitor harvests voltage of 257 mV in 30 minutes.

Abstract:A novel tri-band branch line coupler is proposed for wireless power transmission system.A conventional coupler loaded with quarter-wavelength short coupled lines is adopted to realize the triple passbands.Each passband has a high degree of isolation.The passband center frequencies of the coupler can be adjusted over a wide band by changing the even/odd-mode characteristic impedances of the coupled lines.A planar tri-band coupler located at 0.69/1.0/1.4 GHz is designed and fabricated for verification.Good agreement can be observed between measured results and theoretical expectations.

Abstract:Based on the abstraction of network resource,network virtualization can solve the problem of the rigid structure and poor extensibility of network.Virtual network mapping is the mechanism of mapping the virtual network requests from the user layer to the physical layer with multiple constraints such as CPU capability,link bandwidth and so on.In order to help the virtual network be mapped more efficiently,the balance of node's load is concerned,and the feedback mechanism of the node's load is added to the virtual network mapping algorithm which is based on the principle of proximity.Moreover,the occupied rate of link resource as an evaluation index in k-shortest path algorithm is proposed so as to disperse the link pressure.Because the proposed scheme prefers to choose the less occupied physical link,it will take less time to complete the resource mapping with higher success rate,which strongly improves the efficiency of virtual network mapping.