Wideband Signal Doa Estimation Algorithm And Finding The Fuzzy Problem

Wideband signal has many excellent performances such as good anti-jamming, high resolution, carrying more information, which are helpful for target detection, accurate parameter estimation and feature extraction. It has been widely used in radar, sonar, seismic detection etc, such as ultra-wideband synthetic aperture radar, high range resolution radar and wideband low probability intercept radar. So the wideband signal DOA (Direction of Arrival) estimation becomes more and more important. This dissertation is devoted to the study of two aspects of the wideband signal processing, the DOA estimation algorithms and ambiguity problems of the array. The main researching work and innovation are as follow.(1) Wideband DOA estimation based on coherent signal subspace method (CSSM) and incoherent signal subspace method(ISSM) are summarized and the compare results of the performance of three different focusing algorithms are presented.(2) According to The characteristic of wideband array manifold, we put forward that the change between frequency and the sensor spacing is relative, so we can treat the change of frequency as the variety of sensor spacing. Afterwords we give a wideband signal DOA estimation method by using a virtual array.(3) By using the characteristic that the change between frequency and the sensor spacing is relative, phase-shift method is proposed to produce a virtual array. Through calculating the cross correlation of the narrowband signals and constructing a new toeplitz matrix which is the covariance matrix of virtual array, correlation method is proposed to produce a virtual array.(4) Analyses and Simulations show the proposed method can estimate more DOAs than the number of sensors. There is no need for any focusing matrix, which reduces the computational complexity. The actual spacing between two contiguous sensors is free of spatial sampling theorem, which means that the spacing can be large enough to decrease or eliminate the effect of mutual coupling.(5) The angle ambiguity and the relationship among array shape, aperture and performance of direction finding are studied. The ambiguities of several familiar arrays are compared theoretically and experimentally. With the same condition, such as the number of sensors, array aperture and the interested directions are the same, the uniform circular array performs the best.