Electromagnetic Compatibility Analysis And Research For Low-Orbit Satellite Constellation System

In recent years,with the growth of the demand for broadband Internet access and the reduction of the cost of deploying satellites,a new wave of construction of low earth orbit(LEO)satellite constellation has been ushered in the world,which also means a surge in the demand for frequency resources.However,frequency resources are limited,and the Radio Regulations stipulate that these resources should be used in a fair,reasonable and efficient manner.Applications for satellite frequency and orbital resources made by the competent authorities to the ITU in accordance with the regulations should follow the principle of "First Come First Served,Coordinated Use".Therefore,there is a possibility of the same frequency sharing between different LEO satellite constellation systems as well as between LEO satellite constellation systems and geostationary satellite orbit(GSO)satellite communication systems,which is bound to bring the problem of the same frequency interference between different systems.Therefore,it is more and more important to carry out electromagnetic compatibility analysis and research for LEO satellite constellation system and promote electromagnetic compatibility among different satellite systems.Interference evaluation method and interference avoidance strategy are the two core contents in the study and analysis of electromagnetic compatibility of LEO satellite constellation system,which are also the focus of this paper.Interference assessment methods based on time slicing often require an infinite number of simulation days to obtain relatively accurate statistical results,while statistical results based on spatial probability statistics methods correspond to an infinite number of simulation days.From this point of view,the latter does not need to carry out lengthy calculations and has high simulation efficiency,so it has attracted more and more attention.However,the spatial domain size will affect the computational efficiency and accuracy of the algorithm.To solve this problem,this paper proposes an algorithm which can map the relationship between grid size,calculation accuracy and calculation cost.The algorithm divided the number of grids obtained from the orbital shell according to the grid size set,calculated the number of interfering satellites by combining the probability density function of LEO satellites,used the Monte Carlo algorithm to decouple the distribution of interfering satellites from the constellation configuration,and counted the proportion of the number of interfering satellites falling into the main lobe of the disturbed earth station to the total number of interfering satellites.Compared with the proportion of the intersection area of the main lobe of the earth station beam and the orbital shell of the jamming constellation to the area of the jamming satellite to evaluate the calculation accuracy.The linear relationship between the number of grids and the computing cost is derived and analyzed,and the time complexity formula is used to characterize the calculation cost.The simulation results show that the proposed algorithm can evaluate the influence of the spatial domain size of the spatial probabilistic statistics algorithm on the computational accuracy and computational time complexity,and provide a reference for selecting the appropriate grid size.Setting isolation angle is a common method in the interference avoidance strategy for LEO satellite constellation system.The current research has not conducted detailed modeling and simulation on the solution method of isolation angle threshold,nor has it considered the influence of the uneven distribution of LEO satellites on the orbital shell on the calculation of isolation angle threshold.To solve this problem,a descending interference avoidance algorithm combining the probability density distribution and adaptive isolation angle of LEO satellites is proposed.This algorithm studies the probability density function of LEO satellites,and analyzes the characteristics that the higher the latitude of LEO satellites,the denser the distribution of satellites,and draws the conclusion that in the downlink interference scenario of LEO satellite constellation system to GSO satellite communication system,not only collinear interference near the equator,but also lumped interference at higher latitudes should be considered.The mathematical model of isolation angle and exclusion zone is established,and the modified calculation model of latitude boundary of exclusion zone and distance of interference link is proposed.The interference avoidance strategy of adaptive isolation angle considering collinear interference and lumped interference is designed.The simulation results show that the proposed algorithm can meet the requirements of mitigating collinear interference and lumped interference,and there is no large isolation angle margin,and it can reduce the loss of resource use efficiency of LEO satellite constellation system.