| Nowadays,the development of space technology has become an important direction of national development.China’s BDS is gradually mature,and the possibility of human interference has increased sharply.Therefore,it is urgent to research and develop relevant anti-interference technology to deal with the malicious interference that may appear at any time.This thesis focuses on some key technical points related to anti-jamming in navigation system.It mainly conducts targeted research on many parameters of suppressive interference(such as bandwidth,power,duration,quantity,direction,etc.),and conducts research on several anti-jamming technologies around these parameters.Firstly,this thesis starts with the navigation channel model,analyzes the way that interference is introduced from the channel,and makes a simple analysis of the coerced interference theory.As an anti-jamming method,the anti-jamming method is analyzed.From interference to that on the one hand,anti-interference of several kinds of traditional spatial filtering algorithm analyzed the principle and experimental simulation,several algorithms including:based on minimum mean square criterion of least mean square algorithm(LMS),based on linear constraint criterion of power inversion least mean square algorithm(PI LMS)and sampling matrix inversion algorithm(PI SMI).Through the comparative analysis of several algorithms under different power,different bandwidth,different direction and different amount of interference,the relative advantages and limitations of these algorithms are obtained,which has reference significance for anti-jamming navigation system.Then,some anti-interference technologies under the signal system of BDS are studied.This thesis introduces the signal system of BDS,analyzes the characteristics of ranging code,and introduces some common anti-jamming techniques of BDS receiver system based on software radio.Then the space frequency adaptive anti-jamming technology(SFAP)and interference detection technology are studied,and the anti-jamming effect of SFAP algorithm is analyzed experimentally under the condition that the BDS B3I signal and the absolute best interference are superimposed when the array is receiving.The results show that,on the one hand,compared with spatial filtering anti-jamming algorithm,SFAP has the advantages of resisting more interference and filtering effect in the frequency domain.On the other hand,SFAP not only has poor anti-interference effect,but also has some adverse effects when interference-signal-ratio(INR)is low.In order to avoid such a situation,this thesis proposes an interference detection method based on high-order cumulant,which detects the signal in advance and uses SFAP algorithm when identifying interference.Otherwise,SFAP algorithm is not used to avoid adverse effects.Experimental results show that the detection probability of this interference detection method is greater than 95%when INR is greater than 40dB,which is consistent with the applicable interference power range of SFAP.The combination of these two technologies has certain practical significance.Finally,the non-ideal characteristics in navigation receiver system are studied theoretically and analyzed by simulation,and the countermeasures are given.Experiments are carried out to simulate the adverse effects of several non-ideal characteristics on the anti-jamming effect of spatial adaptive algorithm(PI SMI),which has a certain reference significance for the design of relevant indexes in the system implementation. |
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