Research On Key Technology For Single Observer Passive Location And Tracking

Based on the particle kinematics theory, the dissertation studies the key technologies of single observer passive location via direction of arrival (DOA), rate of bearing and Doppler frequency rate-of-change and nonlinear filter. The principal contributions are summarized as follows:Firstly, the principles of tangential and radial movement measureing distance were introduced, and the error analysis of the passive ranging was performed.Secondly, the method of estimating the direction of arrival was proposed. The phase ambiguity numbers were obtained within the unambiguous scope of each double-baseline direction finding system and the unique set of phase ambiguity number could be acquired through the commnon baselines between those double-baseline interferometers. A method of wideband signal's DOA estimation was addressed. The wideband signal was decomposed into multiple single-tone signals through FFT. The spectrums of FFT within 6dB bandwidth were used to estimate the time-delays individually, and then the accurate time-delay estimate was given by weighting these estimates. The optimal weighting coefficients were given.Thirdly, the estimation algorithms for frequency of coherent pulse train were addressed. High accurate frequency estimation algorithms of coherent pulse train with single and staggered pulse repetition frequency (PRF) were presented. The output signal-to-noise ratio (SNR) was enhanced through intrapulse correlation accumulation. The requirement for coherent frequency estimation was analyzed and the close-form of the input SNR threshold was derived. The relationship of the SNR threshold, the total number of samples and the duty cycle was given for single PRF coherent pulse train. As far as staggered PRF coherent pulse train was concerned, resampling and averaging the phase difference of the sequence according to the number of stagger ratio of the coherent pulse train could reduce the equivalent phase noise. Resolving phase ambiguity through the stagger ratio could enlarge the scope of the frequency difference and decrease the SNR threshold. The relationship of the SNR threshold, the total number of samples, the number of stagger ratio and the stagger ratio was presented.Fourthly, an alternative Doppler frequency rate-of-change estimation algorithm for coherent pulse train was proposed. A suboptimal frequency estimation method was applied to estimate the frequency and the error of frequency estimation was reduced. A new chirp signal was obtained after intrapulse correlation accumulation of the coherent pulse train, of which the frequency rate is the Doppler frequency rate-of-change. Accordingly, it is possible to estimate the Doppler frequency rate-of-change precisely under lower SNR.Fifthly, a novel nonlinear filter was proposed to improve convergence speed and estimation accuracy. The backward prediction and the state update procedure improve the estimation accuracy of the last state estimate and reduce the current state prediction error. A more accurate current state estimate could be gotten with more precise initial condition. Simulation results show that the performance of the proposed algorithm outperforms that of the conventional IUKF in both convergence speed and estimation accuracy.