| As the key link of carrying power flow in MWPT,transmission efficiency is an important indicator to measure system performances.As an important part of the Space Solar Power Station,MWPT is developing in the direction of high power,long distance and high efficiency,which puts forward higher requirements for accurate analysis and experiments.Therefore,several key issues in the modeling and experiment of transmission efficiency are deeply studied in the thesis.The main work of the thesis is as follows:1.A theoretical model of transmission efficiency was established,in the far-near field region of transmitting-receiving antennas.In view of the existing beam collection efficiency,the mechanism of the spatial electromagnetic field of the transmitting and receiving antennas is ignored.And the radar equation is only applicable to the infinite far region.In order to meet the high efficiency and long distance indicators,the receiving antenna is mostly located in the far region of the transmitting antenna and the transmitting antenna is in the near region of the receiving antenna.In this thesis,a new theoretical model of transmission efficiency is proposed.Firstly,the transmission efficiency of the continuous aperture antennas is established based on the Lorentz reciprocity theorem.Then,the spatial mechanism of the electromagnetic field of the transmitting and receiving antennas is clarified.Next,the transmission efficiency of transmitting and receiving arrays is established according to the radiation characteristics.In addition,the relationship between transmission efficiency,transmitting antenna efficiency,beam collection efficiency and receiving efficiency are deeply analyzed.The establishment of this model lays a theoretical foundation for subsequent comprehensive design and large-scale transmission experiments.2.An analytic model for the influence on the efficiency of random amplitude and phase errors in MWPT is investigated.In actual engineering,the phase errors of aperture field are inevitable for transmitting and receiving antennas due to the manufacturing and working environment.The design surface deviates from the ideal one.With the multiple integration in the mathematical expression of transmission efficiency,the calculation become more complicated with the aperture field error distribution substituted directly.In order to quickly evaluate the influence of phase errors on transmission efficiency,a direct correlation model between rms and transmission efficiency is given in this thesis.The simplified transmission efficiency model is applied to a continuous aperture transmission system with random phase errors,which verifies the correctness and effectiveness of the proposed method.For discrete array systems,the excitation error is mostly caused by T/R component output deviation and poor link connection line.Since the excitation deviation mainly comes from the transmitting antenna,the current research focuses on the influence of excitation errors on beam collection efficiency.While,they still have the following problems: firstly,the mutual coupling effect between array elements is ignored,so that there is a large deviation between the statistical analysis results and engineering practice.Second,the large number of array elements and the complex calculation expression of beam collection efficiency will cause large calculation cost when used the Monte Carlo method.In view of the above problems,the correlation of the statistical characteristics between random excitation errors and beam collection efficiency under the mutual coupling effect of array elements is given.Take into the small excitation perturbations,the second-order Taylor expansion is used to establish the correlation model between statistic characteristics of excitation perturbations and beam collection efficiency.By comparing with Monte Carlo method,the accuracy and effectiveness of the model are verified.3.A solution strategy for the transmission efficiency of large array transmission system is proposed.The precise analysis for large array transmission system will bring huge cost in computing time and storage space.The conventional subarray extrapolation can only use for the regular contour of arrays.For the above problem,a method based on the conventional subarray extrapolation is proposed to analyze the large irregular contour array.A feature recognition method is developed for irregular contour geometric features.The entire array with irregular contour can be analyzed by several nonoverlapping subarrays.It can significantly improve the analysis efficiency.Firstly,using a large transmitting array as an example,the comparison with the Multilevel Fast Multipole Method proves that the proposed method can greatly reduce the requirements of computer hardware and calculation time.4.A design method for maximizing transmission efficiency based on radiation field mechanism is proposed.Traditionally,the transmitting and receiving antennas mostly adopt a separate design method.Aiming at the problems that the traditional design method does not consider the field mechanism and cannot obtain the design parameters under the optimal transmission efficiency,an integrated design method for the transmitting and receiving antennas is proposed.For continuous apertures,the optimal aperture field distribution of transmitting and receiving antennas under different constraints is discussed.The design variable are the continuous aperture field distributions of the transmitting and receiving antenna.The design goal is the maximum transmission efficiency,The constraint is the radiation level outside the receiving antenna.Then,this design method is extended to discrete array systems.The maximum transmission efficiency with a given array structure can be obtained by designing the excitation distribution of the transmitting array.The purpose is to get the optimal matching of the transmitting radiation field and the receiving aperture field.Compared with the 10 d B Gaussian distribution,satisfactory results are obtained,which proves the effectiveness of the proposed method.5.A transmission experiment of large-scale terrestrial demonstration and verification system is carried out.Based on the “Zhuri Engineering – OMEGA Space Solar Power Station based on Microwave Wireless Power Transmission”,the spatial electromagnetic field mechanism was experimentally verified.Firstly,the basic situation of the ground demonstration and verification system is summarized.Secondly,the electromagnetic characteristics of transmitting antenna and transmission efficiency of transmitting and receiving antenna are analyzed and tested.Through a large number of experimental data,the proposed transmission efficiency model and solution strategy are fully verified.The key technology of transmitting antenna described in this chapter has certain engineering value and can lay an experimental foundation for the future engineering application of SSPS. |
PDF Full Text Request