DOA And Doppler Shift Estimation In Wireless Location

Direction finding and location is the most widely used technology in wireless passive location, and its basic task is to realize the estimation of direction of arrival (DOA). Most of the existing researches rely heavily on the assumptions that the noise is Gaussian and the source is located relatively far from the antenna array. However, in some scenarios, the noise exhibits an impulsive nature mainly characterized by sudden bursts or sharp spikes, and the source is located in the near-field of the array aperture. On the other hand, a novel interference source location technology based on the Doppler shift of scattering signal has been put forward, and can overcome the drawbacks of the existing monitoring techniques. However, the existing researches mostly focus on the location algorithm, and very little has been done for the estimation of Doppler shift of scattering signal, which is the premise to realize the interference source location. Therefore, the DOA estimation of far-field source in impulsive noise, the near-field source localization and the Doppler shift estimation of scattering signal will be intensively studied in this dissertation.The DOA and Doppler shift estimation are studied in this dissertation, and the main contributions are listed as follows.(1) In order to overcome the drawback that the orthogonal signal subspace and noise subspace cannot be obtained by the eigen-decomposition of the correntropy-based covariance matrix for impulsive noise, a novel correntropy-based cost function is proposed, and the signal subspace is estimated by solving the optimization problem under the maximum correntropy criterion. To solve the optimization problem, an optimal step size based iterative algorithm is developed and the convergence of this algorithm is proved. Furthermore, to reduce the computational complexity, a generalized correntropy is proposed. The boundedness of the generalized correntropy for symmetric alpha stable (SaS) variable is proved, and a DOA estimator based on the minimum generalized correntropy criterion is proposed. Finally, for the DOA estimation for short snapshots and coherent sources, a novel DOA estimator is proposed by fusing the correntropy and the sparse representation. The simulation results demonstrate that the proposed methods are superior to some existing methods in impulsive noise, especially in highly impulsive noise.(2) To reduce the computational complexity and avoid the loss of array aperture existing in the existing fourth-order cumulant based methods, a novel multi-parameters joint estimation method for near-field source is proposed by constructing new cumulant-based matrices, which avoids the loss the array aperture, reduces the computational complexity and improves the accuracy of parameters estimation. Furthermore, to realize the near-field source localization in impulsive noise, a novel method is proposed by adopting the phased fractional lower-order moment (PFLOM). The algorithm avoids the loss of array aperture, the peak search and the parameter pairing. To characterize its performance, the Cramer-Rao bounds for the estimated parameters of near-field sources in Cauchy noise are derived for the first time.(3) For the joint estimation of time delay and Doppler shift in non-cooperative bistatic radar, based on the feature analysis of the short-time fractional Fourier transform (STFRFT) of linear frequency modulated (LFM) signal, a novel STFRFT-based method is developed in this dissertation. The simulation results demonstrate that the proposed method improves the parameter estimation performance in strong noise environments. For the estimation of Doppler shift of aircraft scattering signal, the Doppler shift is approximated by LFM signal based on the feature analysis of Doppler shift, and the estimation of Doppler shift is converted to the parameter estimation of LFM signal. To improve the performance in low duty ratio condition, a novel Gaussian-weighted fractional Fourier transform (GFRFT) is defined, and the output signal-to-noise ratio in fraction Fourier domain is analyzed. Furthermore, to realize the Doppler shift estimation in impulsive noise, a novel phased fractional lower-order moment based fractional Fourier transform (PFLOM-FRFT) is defined, and the feature of complex SaS noise in fractional Fourier domain is analyzed. Both simulation and actual ground experiment results demonstrate that the GFRFT-based and PFLOM-FRFT-based methods can yield accurate estimation for the Doppler shift of aircraft scattering signal.