The Research On Direction Of Arrival Estimation Of Wide-band Signals

Direction of arrival is the most important spatial parameters of the signal. The estimationmethod of DOA is one of the two main research directions in array signal processing. Aftermore than30years’ development, DOA estimation theory and technology has become themain aspects of array signal processing discipline. Its typical applications include radar, sonar,exploration, biomedicine, etc. With the development of signal processing technology, highresolution algorithm based on the narrowband array signal is relatively mature. Thenarrowband array detection system has been widely used in military and civil fields.Compared with the narrow-band signal, wideband signals include more information. It isbetter for target signal detection, parameters estimation and signal features extraction andbecoming more important in active detection and passive detection system. Therefore, theresearch on broadband signal DOA estimation technology has important significance.Based on the classical spatial spectrum estimation theory (mainly related to maximumlikelihood theory, signal subspace theory, cyclostationarity, array error calibration), the paperanalyses direction finding principle and performance of some conventional wideband signalestimation algorithm analysis. Based on the study above, the wideband signals DOAestimation algorithm is studied further. Some new algorithms are presented, and the newproposed algorithms are analyzed and compared with other algorithms in simulationexperiment.Firstly, direction finding technique of maximum likelihood estimation is researched. Themaximum likelihood estimator for wideband signal is obtained from narrowband signalsestimator. Conventional algorithms are mostly based on uniform distribution of Gauss whitenoise background. The paper gives a maximum likelihood estimation method with thenon-uniform noise. It solves the problem in the optimal calculation of closed form, andreduces the search dimensions and the number of iterations. The performance is better thanthe traditional deterministic maximum likelihood estimation algorithm and stochasticmaximum likelihood estimation algorithm.Secondly, the signal subspace DOA estimation technology is researched. By deeplyanalyzing the principle and essence of unitary focusing matrix for coherent signal subspacealgorithm, and under that coherent signal subspace algorithms need preliminary DOAestimation, the paper proposed a new algorithm which obtains the eigenvector througheigen-decomposition of the covariance matrix of array output signals corresponding to different frequencies and focusing frequency. The method does not need preliminary anglesestimation and can process the coherent wideband signals. Computer simulations areconducted to show the better performances of new algorithm. Through the simulationexperiment and comparison with the properties of other conventional algorithm, the algorithmshows better performances.Thirdly, wideband signal DOA estimation technique based on f cyclostationarity isresearched. The paper combines with the cyclostationarity and conjugate cyclostationaritysignal properties and use subspace decomposition method to realize the DOA estimation ofwideband signals. The method utilizes both wide-band cyclostationarity and conjugatecyclostationarity signal information to obtain extended cyclic correlation matrix, inherits theadvantages of Cyclic MUSIC algorithm, and does not need to estimate the time delay inprocessing of wideband signal source. Experimental results show that, this method has a goodselection ability of wideband signal and the ability to identify and can inhibit high powerinterference signal. It has better estimation performance.Finally, the array calibration and DOA estimation in array modeling error is researched.The paper gives various error models (amplitude and phase errors, array element positionerror and mutual coupling effect), analyses the calibration technology of several perturbation,and carries on the simulation experiment with examples. Using some methods, we could notonly realize the array calibration, but also can estimate signal DOA at the same time. Inaccordance with the situation that existing technical conditions can not accurately measureand estimate array error of wideband DOA estimation, using the de-correlation idea of spatialsmoothing technology, the paper proposes a robust method which combines the spatialsmoothing technique and Monte Carlo sampling estimation technique. Theoretical analysisand experimental simulation results demonstrated the ability of the method to eliminate thearray error. The paper puts forward a new way to solve the problem of estimation forwideband DOA array error model.