Research On Direction Of Arrival Estimation And Mutual Coupling Self-calibration In Multipath Propagation

Array signal processing has been applied in many fields such as radar, sonar,communication, seismic prospecting, radio astronomy and so on. Last30years, thedirection-of-array (DOA) estimation has been intensively studied and excellentachievements have achieved. But most of the works are limited to the noncoherentsources by a comprehensive analysis of the existing research results. In practicalconditions, multipath propagation is common due to man-made interference and variousreflective surfaces, such as clouds, hills, buildings, which makes the impinging signalscoherent. Moreover, most of the existing DOA estimation methods require the exactinformation of the array manifold and they suffer form severe perfonnance degradationand even fail in the presence of array error. Therefore many scholars are devoted to theresearch work in the field of array error calibration and put forward many calibrationmethods in recent years. However, there are still many problems in this area need to beresolved. So the thesis focus on the autocalibration method of the mutual coupling andcoherent signals DOA estimation. The main contribution of it can be summarized asfollows:①Mixed-signal DOA estimation and mutual coupling error calibration. Based onalternative iteration，an algorithm is proposed to estimate the DOAof mixed signals andmutual coupling error for uniform linear array (ULA). In the algorithm, a threshold-basedmethod is presented and used to estimate the number of the uncorrelated signals and theDOA of the incoherent signals in mixed signals, and then the corresponding mutualcoupling error is achieved. On the basis of this, the DOAs of the mixed signals areestimated with the aid of a reconstructed Toeplitz matrix. The DOA of the mixed signalsis estimated and the mutual coupling error is updated in an alternative iteration mode. Theeffectiveness of the method has been validated in the numerical examples.②Non-gaussian signals DOA estimation and mutual coupling error calibration.Based on the joint approximative diagonalization of eigen (JADE) matrix method, analgorithm is proposed to estimate the DOA of non-gaussian signals and mutual couplingerror. First, the generalized spatial feature vector of each user is estimated by utilizing theJADE matrix method. Then a transformation matrix is defined, and based on it, thegeneralized spatial feature vector is converted to the one which is related with partelements of the ULA. The multiuser coherent DOAestimates are obtained on the basis of the oblique projection and forward and backward spatial smoothing (FBSS) methods.Finally, a mutual coupling self-calibration method is presented by utilizing the estimatesof the DOA and the generalized spatial feature vector of each user. The effectiveness ofthe method has been validated in the numerical examples.③Multiple groups of non-Gaussian mixed signal DOA estimation and mutualcoupling calibration. Based on JADE, a novel algorithm which includes three steps isproposed to estimate the DOA of mixed signals and mutual coupling coefficient of theULA in presence of the mutual coupling error. In the algorithm, utilizing the Toeplitzstructure of the MCM, the coarse estimates of the DOAs of the uncorrelated signals of themixed signals and mutual coupling coefficients are firstly obtained. Then the DOAestimates of the mixed signals are obtained based on the combination of the obliqueprojection with forward and backward spatial smoothing methods. Finally, a non-subspace method for mutual coupling self-calibration method is presented by utilizing theestimates of the generalized spatial feature matrix and the mixed signals DOAs. Theeffectiveness of the method has been validated in the numerical examples.