Research On Estimation Of Direction Of Arrival In Frequency Diverse Array

With the application and development of array antenna,array signal processing has become an important branch of modern signal processing.Phased array radar has the ability of accurate beam pointing.It is widely applied in the field of parameter detection,estimation and imaging of targets by controlling the beam direction of phased array by the phase shifter at the output end of each array element.Frequency controlled array radar can not only change phase and frequency,but also change its transmitting frequency.It can make the transmitting beam in the same snapshot time no longer point to a fixed angle,which has the characteristics of angular distance dependence and automatic scanning of space beam.It can realize the suppression of distance dependent interference,the transmitting beam and the location of space targets.In this paper,DOA estimation of frequency controlled array is studied.Firstly,the model of frequency controlled array is studied,and the influence of the characteristics and parameters of frequency controlled array on the beam pattern is analyzed.Secondly,aiming at the problem of array aperture loss in the mutual coupling correction,an estimation algorithm for the direction of arrival of frequency controlled array is proposed under the condition of unknown mutual coupling parameters.The Toeplitz structure of the mutual coupling coefficient matrix is used to construct the array flow pattern including the mutual coupling effect,and the sparse spatial spectrum estimation is constructed by using the block sparsity,so that the original problem is transformed into a convex optimization problem.The simulation results show that the algorithm is better than the L1-SVD algorithm and the traditional sparse reconstruction algorithm,and that the DOA estimation accuracy of the frequency controlled array is higher than that of the phased array.Aiming at the problem of the direction of arrival when the far-field and near-field signals are mixed,a direction finding method of the far-field and near-field mixed coexistence is proposed by using the statistical characteristics of the signals.Based on the non-circular characteristics of the signal,a far-field signal estimator is established to obtain the wave direction of the far-field signal.Using the total covariance matrix of the signal,the covariance matrix of the near-field signal is calculated,and finally the wave direction and distance parameters of the near-field signal are calculated.The simulation results show that the proposed algorithm is better than two-dimensional MUSIC algorithm and ESPRIT algorithm based on higher-order cumulant,and it is proved that the parameter estimation accuracy of frequency controlled array is higher than that of phased array.