Research On Radio Direction Finding Technology Based On Unmanned Aerial Vehicle Platform

With the rapid development of radio communication technology,wireless applications have developed rapidly with its ubiquitous convenience,and become an important part of information consumption.At present,radio direction finding technology is not only the key content of military science and technology research,but also the key direction of civil field development.Radio monitoring is to use electronic equipment to search,intercept and analyze the radio signal,and use the radio direction finding technology to locate the transmitting station.Because the current illegal radio equipment and other interference sources are small in size,free to carry,flexible in movement,and difficult to be found and located,the radio direction finding and positioning technology in manual and vehicle mode has been unable to locate the illegal signal sources quickly and accurately,and this mode is time-consuming,labor-consuming and consumable.In view of the current situation of radio monitoring technology,this thesis proposes a radio direction finding technology based on unmanned aerial vehicle platform,which can realize the fast direction finding and positioning of illegal signal sources.It has the characteristics of real-time monitoring,flexible mobile direction finding,etc.,and it can achieve the goal of targeting the places where people and vehicles are difficult to reach but the electromagnetic environment is complex,such as the areas around the airport,along the railway,in the jungle and high mountains,etc Fast search,monitoring and location of illegal or unknown signal sources.In this thesis,the radio direction finding technology is the research content,focusing on the interferometer direction finding technology,passive time difference of arrival location technology,hardware and software algorithm of dual channel direction finding system,time delay estimation algorithm based on triple correlation,etc.The main research content includes the following points.In this thesis,the current wireless direction finding technology is introduced briefly,including the working principle and direction finding characteristics.This thesis introduces the working principle and direction finding characteristics of several radio direction finding systems,including interferometer direction finding system,arrival time difference direction finding system,spatial spectrum estimation direction finding system and so on.Aiming at the traditional direction finding technology of unmanned aerial vehicle platform,the way and method of direction finding are designed and optimized to adapt to the selected SLA-GH170 unmanned aerial vehicle.Firstly,the method of combining interferometer direction finding technology with passive time difference positioning technology is adopted to realize the high efficiency and rapidity of unmanned aerial vehicle platform direction finding technology;secondly,the five element antenna and dual channel receiver which areeasy to carry are selected.Secondly,the basic principle and algorithm of direction finding of correlation interferometer are mainly discussed.Five element circular array antenna is used as the receiving antenna to receive the incoming signal,and two channel interferometer is used as the receiver to send the signal to the processing unit.By building a real-time phase difference sample library,the size of the sample library is reduced and the incoming direction of the signal is determined.Finally,with the increase of the frequency of the signal,the more accurate the phase angle and pitch angle of the signal coming from the direction finding result are,that is,the higher the accuracy of the direction finding will be it.Compared with azimuth,the pitch angle is always accurate and the error is low.Thirdly,aiming at the problem of low accuracy of time delay estimation in passive location at low signal noise ratio,based on the study of traditional cross-correlation method and autocorrelation property,a time delay estimation algorithm based on cubic correlation is proposed.Based on the traditional cross-correlation method,the algorithm makes use of the autocorrelation power spectrum function of two input signals and the traditional cross-correlation power spectrum function to make the amplitude of the signal frequency point in the third correlation power spectrum function increase exponentially,and then weakens the relationship with other small peak amplitude values,so as to achieve the ideal effect of the cross-correlation power spectrum function required for time delay estimation.Finally,for the unmanned aerial vehicle platform,the dual channel direction finding method combined with interferometer direction finding and passive time difference positioning technology is used for joint commissioning.The hardware,function,software and flow of the dual channel direction finding system are mainly introduced.