Research On Parameters Estimation Of Multipath Signals With Vector Channel

The problem of direction-of-arrival(DOA)estimation for non-cooperative sources using the vectorized data collected from an array of sensors has been studied extensively over the past few decades.In practical,the sources may undergo multipath propagation before approaching the receiving array.As a consequence,the incident signals associated with a same source are coherent with each other for narrow-band sources.For this rea-son,estimating the DOA of coherent signals has been a hot topic in this field.To fully depict the multipath model,the multipath parameters,including the DOAs,fading coeffi-cients and source association are needed.However,most of the existing direction finding algorithms have ignored the connections among different multipath parameters.To address this problem,this thesis mainly focuses on studying the multipath model for the cases of circular Gaussian(CG)sources and strictly non-circular(SNC)sources.More specifically,the effect of source association information on the performance of DOA estimation is studied through Cramér-Rao bound(CRB)analysis.Algorithms are developed to estimate the multipath parameters.Moreover,the problem of sensor gain-phase errors calibration is also discussed to meet the need of practical application.The main contributions are summarized as follows.1.The CRB of multipath model(MCRB)for CG sources with the prior information of source association is derived.The difference between the MCRB and the traditional CRB without considering the source association is analyzed.Analytical and numerical results demonstrate that using the information of source association can reduce the CRB significantly when incident signals can be classified into more than one group of coherent signals.2.The multipath model for CG sources and its eigenstructure are analyzed,based on which,estimation algorithms applying to arbitrary array and methods specially designed for uniform linear array(ULA)are developed.A coarse DOA estimation obtained by an existing method is needed for implementing the proposed methods,except that the ULA based source association estimation algorithm can estimate the coherent structure using only the array output.Meanwhile,in comparison with the algorithm applying to arbitrary array,the ULA based direction finding method has a lower computational complexity.Simulation results show that the source association estimation methods can estimate the source association effectively in mild conditions,and remarkably improved performance can be achieved by the proposed direction finding methods.In addition,an joint estima-tion algorithm for all the multipath parameters is also proposed for the case that incident signals are spatially inseparable.Simulation results show that the proposed algorithm can also closely approach the MCRB in this case.3.A low-complexity direction finding algorithm is proposed for the case of SNC sources with centro-symmetric array.The proposed method can simultaneously esti-mate the DOAs and non-circular phases,and has a comparable performance compared to the NC-MUSIC algorithm when the separation of non-circular phases is large enough.Meanwhile,the stochastic CRB for SNC Gaussian sources without considering the source association is derived and analyzed as well.The analytical and numerical results demon-strate that a significant performance gain can be achieved by investigating the property of SNC sources when the sources are incoherent.For the case that incident signals are fully coherent,an obvious performance gain can also be obtained in certain conditions.4.The multipath model for SNC sources and its eigenstructure are analyzed,based on which,estimation algorithms for source association,fading coefficients and DOAs are developed.Meanwhile,closed-form expression of MCRB for SNC sources is derived as well.The proposed direction finding algorithm makes full use of the source association information and the property carried by SNC sources.Simulation results show that the proposed algorithm outperforms the traditional methods,and can closely approach the MCRB of SNC sources.5.A non-iterative method using SNC sources is proposed for sensor gain-phase er-rors calibration of centro-symmetric array,and the corresponding CRB is derived.The proposed method is realized through two steps:spatial signatures estimation and parame-ters estimation.The proposed method offers a number of advantages in comparison with the existing methods.First,the DOA estimator is independent of the sensor phases.Sec-ond,the proposed method applies to incoherent sources.Third,the proposed method is capable of providing 360~°azimuthal coverage under certain conditions.Meanwhile,the CRB is decreased by introducing the property of SNC sources,and the proposed method is capable of achieving the CRB in mild conditions.