Research On Spaceborne Single-Based Synthetic Aperture Passive Positioning System And Technology

With the rapid development of space militarization,because electronic reconnaissance satellites can obtain battlefield information in all-weather,all-day,and global observation ranges,spaceborne passive positioning technology has become more and more important.The existing research on spaceborne passive positioning technology is usually based on data measurement at multiple times.It does not use the coherent characteristics of the emitter signal and it is affected by the measurement error,so the positioning error is large.The spaceborne synthetic aperture positioning system is proposed as a new important system.In the synthetic aperture radar,the high resolution in the range direction is only limited by the frequency bandwidth of the signal and it is achieved by range pulse compression,the high resolution in the azimuth direction is to use the relative motion between the SAR platform and the radiation source.Compared with the existing spaceborne passive positioning,the positioning technology of synthetic aperture can acquire high-precision positioning of the radiation source comparable to the accuracy of SAR images.The research of the thesis revolves around the spaceborne passive positioning technology based on synthetic aperture.The main work of the paper is showed as follows:1.A systematic study of single-star fast and high-precision positioning based on synthetic aperture.Firstly,by introducing the idea of synthetic aperture into spaceborne passive positioning,a space-borne synthetic aperture broadside positioning model is established.Based on this model,its positioning principle is expounded,and the expressions of matched filter and azimuth chirp-rate are deduced emphatically.At the same time,for the problem of large distance search range,a two-step search method is proposed to reduce the amount of calculation and realize rapid and high-precision positioning of radiation sources.Then,because the coherence of the signal is used,several signal coherence recovery methods are introduced.Finally,the proposed positioning principle is verified and analyzed by simulation experiments.2.A wide-beam squint positioning method based on synthetic aperture is proposed.Firstly,a wide-beam squint positioning model based on synthetic aperture is established,and then a single-satellite positioning method based on Doppler and azimuth chirp-rate is proposed,the estimation of azimuth chirp-rate and the establishment of positioning cost function are deduced.Aiming at the problems of Doppler center shift and carrier frequency measurement error having great influence on Doppler estimation in this method,a dual-satellite joint positioning method based on azimuth chirp-rate is proposed,and the two proposed positioning methods are simulated and verified respectively.3.The multi-radiation source positioning method is studied,and the multi-domain separation method of the signal is proposed,including separation from the common time domain,frequency domain,etc.The time-frequency analysis tool is used to filter the aliased signal,in which the fractional Fourier transform is used to separate multiple LFM signals,Aiming at the synthetic aperture positioning method,a signal separation method of multiple radiation sources based on synthetic aperture is proposed according to the characteristics of the signal.Finally,the simulation analysis is carried out in the scenario of multiple radiation sources.