Research On Key Technology For Signle/Dual Satellite Passive Localization

The localization of target radiation on the earth by satellite is the key step of space electronic reconnaissance. In this thesis, we propose accurate estimation algorithms of the parameters that applied to single(dual) satellite passive location, and an equation solution for single satellite radial acceleration passive location. The main contents are shown as following:Firstly, we introduce coordinate systems that commonly used in spaceborne passive localization and their transformations, as well as principles and accuracies of passive location systems. After that,a single satellite localization method using the particle swarm optimization(PSO) search technique to obtain the optimal solution is proposed. Theoretical analysis and computer simulation indicate that this localization method avoids the problem of initial value selection and is easy to implement with small computation and could be widely used.Secondly, the time of arrival(TOA) estimation algorithm based on the Haar wavelet and the time difference of arrival(TDOA) estimation algorithm based on correlation function are introduced. Common TDOA estimation results are mostly integer times of sample interval, which will result in errors of measurement principle. Two TDOA accurate estimation algorithms based on time-phase transformation and time-frequency transformation respectively are proposed in the thesis. According to the simulation results, the TDOA estimation accuracy of time-phase transformation algorithm is close to the Cramer-Rao lower bound(CRLB) when the signal to noise ratio(SNR) is more than 6d B. The TDOA estimation accuracy of time-frequency transformation algorithm is close to the error lower bound when the signal to noise ratio(SNR) is more than 6d B. TDOA estimation precision is improved as the signal bandwidth increases and is not affected by signal modulation mode.Thirdly, direction finding by interferometer of narrow-band signal is studied. The principle of direction finding method based on baseline ratio by one-dimensional interferometer is introduced. The method is limited of baseline length. A kind of long baseline unwrapping phase ambiguity algorithm is presented. Multipling the baseline length and using the TDOA that signal arrives at adjacent arry elements of the baseline to correction part of the phase difference. The residual phase difference satified the request of the baseline ratio mathed. The conditions and probability of unwrapping phase ambiguity is given. Theoretical derivation and simulation results show that high accuracy can be achieved in direction finding by setting baseline length as long as it meets the far field conditions.Fourthly, the frequency difference estimation method based on cross-ambiguity function for narrow-band single pulse signal and Doppler frequency rate estimation algorithm for narrow-band coherent pulse train(CPT) were introduced. Under the condition of non-cooperative, the Doppler frequency difference and rate accurate estimation for broadband signal is difficult to achieve due to the mismatch between the sampling period and pulse repetition period. According to the relationship between radial velocity, radial acceleration and the pulse repetition interval, the radial velocity difference and radial acceleration estimation algorithms for broadband signal were presented. These two algorithms only need accurate measurement of pulse delay and are uninfluenced by the source wave signal parameters such as frequency and modulation method. The greater the bandwidth is, the higher the precision is. Radial velocity difference estimation algorithm does not need a large amount of data transmission between two satellites, so it is easy to implement.At last, a parameter blind estimation algorithm of Costas frequency hopping Signals is presented in this thesis. Comparison with other algorithms, this algorithm has the characteristic of shorter computation time and higher parameter estimation accuracy. It can deal with pulse width unknown situation. Simulation results indicate that it’s effective even at low signal to noise rate(SNR).