Research On Two-dimensional Direction Finding Technology Of Narrowband Array Signal

Direction finding,also called direction of arrival(DOA)estimation,refers to a sensor array composed of some sensors that are arranged in a certain way and distributed in the different space,receiving radiating signals,then specific processing is operated on them.In this way,the interested target signals are enhanced while the unwanted interference and noise signals are suppressed,which can extract the useful parameters of signals.Having been widely applied in many areas such as seismic exploration,wireless communications,biomedical imaging and so on,DOA estimation is an important area of array signal processing research,and many high resolution algorithms have come out in the past decades.Firstly,some base knowledge of direction finding is introduced,including mathematical model of array signal processing and several classic direction finding algorithms.And then based on narrowband signal,this thesis focuses on the two-dimensional(2-D)direction finding algorithms of multipath coherent signals,noncircular signals,etc.Based on two parallel uniform linear arrays(ULAs),a new high-resolution approach called FOC-based Toeplitz matrices reconstruction(FOC-TMR),is presented for 2-D DOA estimation of incident narrowband coherent signals.The angle estimation problem is addressed by arranging the cumulants elements of received signals from two parallel ULAs to two Toeplitz matrices.In Gaussian noise cases,it is shown that the ranks of the two Toeplitz matrices equal the number of the incoming waves and are independent of their coherency.In the condition of two closely spaced coherent signals in both 2-D angles,simulation results show that,in comparison with the FOC-based forward spatial smoothing(FOC-FSS)method,the proposed algorithm has lower computational complexity and yields better estimation performance.Using three-parallel ULAs,an improved 2-D DOA estimation method is proposed with linear propagator method.The proposed method constructs the signal subspace by a linear propagator,which reduces the computation.The 2-D DOA estimation problem is addressed by making full use of elements of the three-parallel ULAs,thus the angle estimation accuracy is improved.Furthermore,the proposed algorithm has better angle estimation performance in practical mobile elevation angles between 70° and 90°.Assume the incoming signals are deterministic,the deterministic Cramer-Rao Bound(CRB)with three parallel ULAs is studied.Numerous simulation results demonstrate the effectiveness of the proposed algorithm.Based on the principle of rank reduced and joint diagonalization technique,we propose two 2-D finding algorithms for a mixture of circular and non-circular sources.The two proposed methods build array models respectively,which are applicable to mixed circular and non-circular sources,and can distinguish circular and non-circular sources.The two proposed algorithms also can automatically pair the 2-D DOAs,simulation results are provided to verify the effectiveness of the two proposed methods.