Research On High-resolution Direction Of Arrival Estimation Techniques For Coherent Signals

As the array signal processing theory and the practical application get rapid develop-ment, the theory and technology of direction of arrival(DOA) estimation also have become more sophisticated. In the actual environment, because of natural reflections of clouds, mountains and buildings, or the effect of artificial intentionally or unintentionally interfer-ence, there are coherent signal abounding. DOA estimation of mixed signals, which contains non-corrected signals and coherent signals, has become an important problem. Compared with non-coherent signals, coherent signals will cause rank deficiency of the noiseless cor-relation matrix of received signals. Those high-resolution sub-space algorithms for non-coherent signals will fail in this condition. At present, there are many domestic and foreign scholars studying in this field, trying to find a DOA estimation algorithm for coherent sig-nals, which has higher precision, low-complexity calculation, higher sensor utilization and better robustness. In this dissertation, the DOA estimation method for coherent signals was studied, the basic idea is to rearrange the correlation matrix and expand the array configura-tion.1. A new covariance matrix reconstruction algorithm based on additional reference sen-sor was proposed. The algorithm constitutes a new Toeplitz matrix with cross covariance of output of the additional reference sensor and all the other sensors. The reconstructed matrix does not contain autocorrelation noise, so it is suitable for non-uniform Gaussian white noise environment. At the same time, the proposed method has advantages of matrix reconstruction algorithm and the propagator matrix algorithm. It is proven that in the1-D condition, the effective array aperture is M/2in an M-dimension ULA. Then we general-ized the proposed method to2-D estimation problems, using the L-shaped array and double parallel uniform linear array. The algorithm can successfully estimate the DOA of coherent signals2. The dissertation analyze the impact of elements spacing to find angle ambigui-ty. Combining with the ABMR algorithm and extended array, this dissertation proposed one-dimensional linear expanded aperture array and two-dimensional L-shaped expanded aperture array. Low accuracy unambiguous estimation and high accuracy cyclically am-biguous estimation of DOA are obtained from eigenvalue and eigenvector, respectively. The proposed method uses the low accuracy unambiguous estimation to resolve the ambiguity of the high accuracy cyclically ambiguous estimation. Then high accuracy unambiguous es-timation can be achieved. The simulation results verify the validity of the proposed method.3. A new method to classify the two-dimensional(2-D) directions of arrival(DOA) es-timation of signals in a coherent environment is proposed. By using the dual-size spreading array, which is formed by spreading a sub-array along a trail-array, the correlation matrix can be rearranged to form a new matrix, whose rank depends on only the number of in-coming waves. This new method can both enlarge the effective aperture and reduce the computational complexity of DOA estimation.4. Besides the traditional forward matrix reconstruction method, backward reconstruc-tion matrix was introduced. By combining the forward rearranged correlation matrix with its conjugated backward form together, it is always possible to estimate any2M/31-D DOAs using M-element ULA and any2(3-2(?)2)MN2-D DOAs using M×N-element URA. The effective aperture is the same as the forward/backward spatial smoothing method, which is greater than the traditional reconstruction matrix. The proposed method could both enlarge the effective aperture and reduce the computational complexity.