| The characteristics of low earth orbit micro satellites are low cost,short cycle,and can provide ubiquitous low cost communication and navigation services through constellation networks.In recent years,research and construction boom of narrow band mobile satellite service system and communication-positioning integrated technology have been developed all over the world.In order to save launching costs and shorten the deployment cycle,low earth orbit satellite constellations often use one-arrow layout for launch deployment.The spaceborne antenna is installed outside the satellite,which directly determines the size of the satellite envelope,thus affecting the multi-satellite layout.Most of the operating bands of narrow band internet of things communication and high precision navigation augmentation applications are below 2GHz,corresponding to large electrical size and more urgent demand for antenna miniaturization.At the same time,based on business application scenarios,the satellite also puts forward requirements for multi-band and flexible switching of radiation characteristic parameters in orbit,and puts high requirements for the antenna gain,axis ratio and the accuracy.The existing antennas can not balance the above small size,multifunctional and high performance simultaneously,and have become one of the bottleneck problems in the application of low earth orbit small satellites in narrow band Internet of Things communication and high precision navigation enhancement.Therefore,according to the size,function and performance requirements of the application scenario,the mini-frequency antenna with multi-frequency band antenna,hybrid reconfigurable antenna with flexible adjustable frequency polarization parameters and beam scanning phased array focusing on frequency band,power capacity and insertion loss.At the same time,the paper fully considered the adaptability of the spaceborne environment,optimized the design of the relevant parameters of the antenna design,and some of the results completed the in-orbit flight verification.The research content mainly includes the following four aspects:Firstly,in order to realize the small frequency interval of the d ual band antenna,the small frequency ratio of the quadrifilar antenna.According to the active Z parameter theory and the classical resonant antenna theory,we can clarify the resonant characteristics of the antenna radiator under different structures and guide the design and evolution of the radiator,and establish the relatio nship of geometric parameters on the key indicators such as dual band frequency ratio and standing wave of the port.A radiator with the combination structure of "inverted U-shaped helical strip" and "top cross metal strip" is proposed,which achieves the axial gain,axial ratio and wide beam gain index better than the similar design in the small size and doual band.By analyzing the resonant current distribution on one radiator element,this thesis discusses its resonance modes in two operating bands and provide the theoretical basis for frequency ratio tuning and radiation performance optimization parameters.The design effectiveness and accuracy are verified by electromagnetic field full wave simulation optimization,testing and in orbit test.Secondly,in order to consider the miniaturization and high-precision performance of the four band navigation receiving antenna,this paper will study the high-precision miniaturized design of the back cavity patch antenna of the spaceborne choke ring.For the first time,the antenna theory was used,and the key geometric parameters and change rules were found and summarized.Accordingly,a curved wall choke ring structure is proposed,and the antenna dimension is significantly smalle r than the same antenna.Through parameter analysis and joint optimization,the high-precision indexes inside and wide beam under four working band of GPS L1/L2 and BDS B1/B3 are realized,comparable to the standard choke loop performance.Verification design effectiveness and accuracy through simulation,testing and in orbit tests.Thirdly,reconfigurable antennas have greater flexibility than multi-band antennas.In order to realize the flexible and independent reconfiguration of frequency polarization parameters and reduce the number of electric adjusted components,this paper will study the spaceborne miniaturized frequency and polarization hybrid reconfigurable antenna with flexible and independent characterastics.The frequency reconfiguration characteristics of antenna radiator are analyzed by using active Zparameter theory and resonant current distribution;a three-unit PIFA antenna varactor loading method is proposed,which can improve the frequency reconstruction bandwidth and reduce the loss of electronic tuning devices;a three-unit PIFA antenna converter is proposed to improve the bandwidth,by using the principle of three point sequencial feeding,a polarization reconstruction network with single switch control is proposed.Independent hybrid reconstruction of frequency and polarization is achieved using less reconstruction devices and simple peripheral circuits.Continuous frequency reconstruction is realized in the working frequency band,and the left and right handed polarization reconstruction is independent of each other;at the same time,its simple circuit and excellent performance make it have obvious advantages over the design of similar antennas,and suitable for spaceborne application.Verification design effectiveness and accuracy through simulation and testing.Finally,in order to realize the multi degrees of freedom of frequency and polarization parameters and improve the functional integration of spaceborne antenna,at the same time,aiming at the bottleneck of improving the performance indexes such as phased array working bandwidth,power capacity and insertion loss,the research on spaceborne miniaturized array element rotating phased array without phase shifter is carried out.Based on the theoretical analysis of the circular polarization antenna rotating along the symmetry axis,the thesis propose a small rotating phased array with a beam scanning capability of ±50° within the operating frequency range,and the beam scanning scope is comparable to that of the traditional phase shift method,and avoiding the bottleneck problems of narrow bandwidth,low power capacity and higher loss caused by the phase shifter.Based on the theoretical analysis of circular polarization antenna rotating along the axis of symmetry to realize phase offset,a miniaturized circular polarization array element rotating phased array is proposed,which has the beam scanning ability of ±50° in the operating frequency band.Its performance on beam scanning is equivalent to the traditional phase-shifting method,and it avoids the bottleneck of narrow bandwidth,low power capacity and high loss by architecture design.Based on circular polarization antenna principle and far-field superposition principle,the corresponding relationship between the rotation angle of circular polarization array element and its far-field phase is obtained,and the array element selection and array comprehensive design are carried out.In this thesis,rectangular and triangular grid arrays with eight elements are realized to achieve beam scanning ability of ±50° and axial gain of 8～11d Bi in the scanning range,which is equivalent to the performance of traditional phased array.The array architecture has been verified by simulation and test. |
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