Research On High Precision Muti-Satellite Passive Localization Based On Time Of Arrival And Frequency Estimation

Passive localization has been a research hotspot because of its passive working characteristics.It has advantages including high concealment,low probability to be interferenced and strong survivability in electronic warfare.This paper mainly studies the signal processing methods of passive positioning systems on platforms such as satellites and missiles.These platforms have the characteristics of limited communication capacity and weak hardware processing ability.To deal with these feastures,this paper:(a)respectively estimates the time-difference-of-arrival(TDOA)and frequency-difference-of-arrival(FDOA)measurements based on time-of-arrival(TOA)and frequency-of-arrival(FOA)estimation;(b)solves the TOA pairing ambiguity problem when generating TDOA via TOA,and(c)uses the TDOA and FDOA measurements to locate line-of-sight targets on the earth surface.Without loss of generality,this paper considers four satellite and two satellite platforms in the study.The specific contents are as follows:(1)The study of high-precision TOA and FOA estimation methods based on time-frequency-analysis,which are applicable for a variety of signal types.With respect to TOA estimation,the optimal complex Morlet wavelet transform method is proposed to alleviate the drawbacks of conventional methods which have low accuracies or poor adaptive abilities.The advantages of the proposed method include: adaptive parameter selection ability,wide applicability to multiple signal types and high TOA estimation accuracy.Further,a HT-STFRFT method is proposed specially for the LFM signal to enhance TOA estimation accuracy by fully utilizing the LFM signal characteristics.Hence,its noise robustness is higher than that of the optimal complex Morlet wavelet transform method.In the aspect of FOA-based FDOA estimation,the traditional FFT method has lower frequency resolution,and the multiple signal classification(MUSIC)method has a higher complexity of eigenvalue decomposition.To make improvements in terms of FOA estimation accuacy and computational complexity,the PM-MUSIC method is proposed in this paper which can maintain the high estimation performance of the MUSIC method while reducing the computational complexity.(2)The study of ambiguity-free TOA pairing method,which helps avoid TDOA measurement errors which are the multiples of(PRI).Due to the poor performance of traditional ambiguity-free TOA pairing method in two satellite scenarios,this paper proposes an improved analytical method to improve the success rate of defuzzification by sacrificing the computational complexity.(3)The research on high-precision passive location algorithm based on semi-definite programming.In particular,the TDOA-FDOA-AOA joint localization algorithm is proposed for the two satellite scenario,which is achieved by building a new convex optimization matrix and involving the earth surface constraint.Consequently,positioning problem is solved in high accuracy and the unstable convergence property of some traditional methods are avoided.Finally,the simulation tests are carried out in the MATLAB software environment.The simulation results show that the proposed algorithms in the above three aspects have certain performance improvement under certain conditions,and that the high-precision parameter estimation and high-precision positioning are generally realized.