| Solar rectifying-antennas(rectennas),much different from the conventional photovlotatic(PV)cells,are based on the wave character of light.Optical antennas are used to receive the solar radiation,and then optical rectifiers are coupled to transfer the AC current to DC current.Due to no limitations of the material bandgaps,their conversion efficiency can reach more than 85% in principle.Moreover,the materials for solar rectennas are more easily accessible and inexpensive than PV cells.However,as a system,the solar rectennas are related closely to other component parts and affected by a number of factors.Furthermore,due to the high working frequency,the research method of solar antennas has much difference with that of low-frequency microwave rectifier antennas.It is found that there are still several key problems to be solved in solar rectennas: 1)the scientific characterization of solar rectifier antenna conversion efficiency;2)the theory and design of efficient full-spectrum receiving antenna;3)the structure and related research methods of optical frequency rectifier;4)the integrated design of solar rectennas.In this dissertation,the theory associated with solar rectennas is added.Fully considering various factors such as coherence,polarization,radiation,matching,rectification and so on,a full-spectrum receiving antenna with high efficiency is proposed,the quantum rectification theory based on the transfer-matrix methodology is applied to analyze the rectification characteristics of the asymmetric diode with a needle tip,and then the integration of solar rectifier antenna is studied.It is indicated that the final conversion efficiency can truly reflect the current level of the solar rectennas.This dissertation includes:1.A reasonable expression is presented for evaluating the efficiency of solar rectennas.Compared with the existing evaluation systems,the polarization matching efficiency between the antenna and solar radiation,the radiation efficiency and effective area of an antenna,the matching efficiency between the antenna and rectifier and the rectifier efficiency are considered synthetically,which makes the evaluation standards of the solar rectennas more comprehensive.2.The relationship between the intensity of the near-field and antenna impedance,polarization,radiation and other characteristics is established.According to the relationship,a butterfly feeding gap and an extended hemispherical lens are applied to obtain a higher near-field enhancement ratio,which lays a foundation for the design of solar rectennas.3.In view of the limitations and deficiencies of traditional optical antennas in receiving solar radiation,a full-spectrum efficient receiving antenna is proposed.It is found that this antenna with the material of silver is more suitable as a full-spectrum solar receiving antenna.4.Based on the theory of transfer-matrix quantum rectification,the rectifying ability of the tip MIM diode is analyzed,and the results are compared with the classical rectification theory and the semiclassical Tien-Gordon theory.It shows that the quantum rectification provides a method guarantee for the research,analysis and design of solar rectennas.5.The integrated theoretical design of solar rectifier antenna is proposed.The mutual coupling effect between array elements is analyzed;for the problem of low induced voltage at the antenna terminal,a concentrating device scheme is studied and proposed;for the matching and rectification of diodes,the influence of metal work function and tip height is studied and analyzed,and the rectification performance of diode is optimized;the results show that the conversion efficiency of the integrated solar rectenna reaches 2.2%,compared with the existing models,which are less than0.1%. |
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