| With the wide application of satellite Internet system represented by "Starlink",it marks that modern satellite communication has entered a new period of rapid development.As a typical low profile passive phased array antenna,Variable Inclination Continuous Transverse Stub(VICTS)array antenna has the technical characteristics of high gain,low profile,miniaturization,low power consumption and very low satellite interference.It has broad application prospects in many important fields such as mobile satellite communication and fast satellite signal reception.However,compared with the traditional parabolic antenna,the instantaneous bandwidth of the low-profile passive phased array antenna represented by VICTS is relatively narrow,which becomes the bottleneck problem restricting its application in the field of high-throughput satellite communication.In this dissertation,the instantaneous bandwidth expansion of VICTS antenna is studied.The main research contents and innovations are as follows:1.To solve the problem of narrow instantaneous bandwidth of VICTS antenna,a method of instantaneous bandwidth expansion of VICTS antenna based on subarray synthesis is proposed.Firstly,by establishing the aperture field and array pattern model of VICTS antenna,the reasons for limiting the instantaneous bandwidth of VICTS antenna are analyzed,and the relationship between phase and delay between subarrays of VICTS antenna is studied.It is proved that the subarray synthesis of different rotation angles can be ensured by using fixed delay.On this basis,the calculation formula of delay compensation of VICTS antenna is derived.The correctness of the formula of delay compensation is verified by simulation.Secondly,based on the antenna array theory,the influence of VICTS antenna subarray structure on the instantaneous bandwidth is analyzed,the theoretical limit of the maximum instantaneous bandwidth is derived,and the correctness of theoretical analysis is verified by calculation.Finally,a design method of large instantaneous bandwidth VICTS antenna based on subarray synthesis is proposed.By using feedback coaxial true time delay power splitter structure and small size multi-layer line source generator structure,the wideband true time delay power distribution is realized and the transverse field distribution uniformity is improved.Simulation and measurement results show that compared with traditional VICTS antennas,the proposed method can increase the instantaneous bandwidth of 3/4d B from 2.5% to 5%.2.In view of the problems that the subarray synthesis method cannot change the scanning characteristics of the subarray beam and the sidelobe deterioration,combined with the subarray synthesis structure,a method of instantaneous bandwidth expansion and optimization of VICTS antenna based on negative group delay structure is further proposed.Firstly,by analyzing the beam scanning characteristics of VICTS antenna,the negative group delay structure is proposed to effectively suppress the frequency scanning of VICTS antenna.Then the transcendental equation of the propagation constant of the negative group delay slow wave structure is derived by using the field theory,and the equivalent circuit model is established,and the correctness of the model is verified by simulation and practical test.Secondly,a design method of VICTS antenna with large instantaneous bandwidth based on negative group delay structure is proposed.Simulation verification is carried out,and the antenna is processed and tested in the microwave darkroom.The simulation and measured results show that compared with the traditional VICTS antenna,the instantaneous bandwidth of 3/4d B can be increased to 12.5%.Finally,to solve the problem that the resonant characteristics of traditional periodic slow-wave structures are difficult to adapt to wideband design,quantum genetic algorithm is used to optimize the parameters of the reactance loaded transmission line model,and map them to the size parameters of the slow-wave structure.A wideband flat negative group delay slow-wave structure is realized to expand the instantaneous bandwidth of VICTS antennas.3.In order to solve the problem of large propagation loss of negative group delay method using slow wave structure,a method of instantaneous bandwidth expansion and optimization of VICTS antenna based on negative group delay structure is proposed on the basis of subarray synthesis and negative group delay structure.Firstly,according to the beam scanning characteristics of VICTS antenna,the generalized Snell theorem is used for analysis,and the negative group time-delay metamaterial is proposed to reduce the beam scanning amount of VICTS antenna.Secondly,the parameters of the metamaterial equivalent circuit model are given by analyzing the metamaterial structure,and the correctness of the model is verified by simulation and actual test.Finally,a design method of high instantaneous bandwidth VICTS antenna based on transmission line metamaterials and transmission metamaterials is proposed.The simulation and experimental results show that,compared with the traditional VICTS antenna,the two metamaterial-based VICTS antenna instantaneous bandwidth expansion methods can increase the3/4d B instantaneous bandwidth to 12.5%. |
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