Research On Localization And Polarization Parameter Estimation Algorithm Of Near And Far-Field Sources

There are complex composites between near field(NF)and far fields(FF)for passive positioning in applications such as radar,electronic/underwater warfare and mobile communications.Traditional source localization has problems such as simple model,no analytical solution and complex operation,strict array arrangement,model mismatch,and difficult separation of NF and FF source information.Based on co-central orthogonal loops and dipoles(COLD)array and multiple signal classification(MUSIC)method,the near field parameter and composite field parameter estimation algorithm is proposed in this dissertation.And the effectiveness of the algorithm is verified through numerical and semi-physical simulations.The specific research contents are shown as follows:Simplified models are adopted in most of existing near-field source localization algorithms,for example,the Fresnel approximation model.Unlike these works,a none approximation algorithm is herein proposed to localize multiple near-field electromagnetic sources under the exact source-array propagation model,which is called NA-NFSL(None Approximation-NF Source Localization).Using the data measured by a linear(not necessarily uniform)COLD array,three cumulant matrices are firstly defined to construct two matrix pencils.The magnitudes of the two matrix pencils’ generalized eigenvalues are then combined with their phases to extract the direction-of-arrival(DOA)and range estimates of the sources.The key idea of the new algorithm is to resolve the set of ambiguous estimates obtained from the phases using a set of coarse estimates obtained from the magnitudes.In addition,the proposed algorithm estimates the polarizations without needing the prior estimation of the DOA-range parameters.This proposed algorithm is analytic,requires no iterative computations,and does not need to confine the inter-element spacing to be within a quarter wavelength.A none approximation-hybrid field source localization(NA-HFSL)algorithm is proposed to localize a hybrid of NF and FF sources in this dissertation.The MUSIC estimator for localizing the FF sources is referred to as the FF-MUSIC estimator.On the other hand,the NF-MUSIC estimator is designed for localizing the NF sources as well.In between the processing of these two estimators,the Capon spatial spectrum is exploited to reconstruct a pure NF covariance matrix.The proposed algorithm requires only several one-dimensional(1-D)spectral searches and does not involve any computations of highdimensional iterative optimization,higher-order cumulants,and parameter pairing.Unlike the existing algorithms,which are derived based on the second-order Taylor series approximation,i.e.,Fresnel approximation,of the spatial phase factor,the proposed algorithm is applicable to any-order expansion of the spatial phase factor.Moreover,it works well for non-uniform arrays,whereas the existing algorithms can only be applied to uniform arrays.Many mixed NF and FF source localization algorithms in the published literatures are proposed based on the Fresnel approximation model,which is a simplified model of the exact source-array spatial geometry.Unlike these algorithms,a field separation-based hybrid field source localization(FS-HFSL)algorithm is derived to localize a mixture of NF and FF electromagnetic sources based on the exact spatial model with the use of a linear COLD array.The summation of the dipole covariance matrix and the loop covariance matrix is shown to be independent of the source polarization parameters.Using this property,a MUSIC pseudo-spectrum is defined for joint angle and range estimation.To facilitate the computational efficiency of the algorithm,a set of coarse angle and range estimates are derived using the estimating signal parameter via rotational invariance techniques(ESPRIT)philosophy to initiate the MUSIC searching.The major advantage of the proposed algorithm over the existing algorithms is that it does not introduce the systematic errors caused by the mismatch between the source-array propagation model and the Fresnel approximation model.Using the physic sources,TR antennas and data collection devices,a simulator of hybrid field source localization is designed,which is used to verify the efficiency of the proposed algorithms about FF and NF sources localization.The advantage of the adaptability for the un-uniform leaner array is also proven.Summarized,the NF sources positioning and the hybrid field sources positioning algorithms are proposed in this dissertation based on MUSIC algorithm and the COLD array.The proposed algorithms use accurate model with high calculation efficiency,no model mismatch problem,and suitable for all kinds of array arrangement,which can provide good theoretical guidance for the engineering application of hybrid field source passive positioning algorithm.