Passive Radar Direction Finding Techniques Based On Wide Band System

It is about the problem that passive direction finding techniques faced in actual engineering application. It mainly studies on such aspects of interferometer direction finding method of arbitrary array, improving resolution performance of MUSIC (Multiple Signal Classification) algorithm and calibration method of amplitude-phase mismatch in actual direction finding system, and corresponding methods are proposed. The software and hardware of direction estimation processor is designed and debugging at the same time. The proposed methods are tested in actual direction finding system, and their feasibility is proved adequately.Direction finding method of spatial baseline is proposed based on interferometer method. It can realize unambiguity estimation of directon of arrival with arbitrary arrays in wide band. Its direction finding model is established and the relationship between phase difference of two arbitrary antennas and direction of arrival is derived. It realizes estimating the direction of arrival by constrrcting equations. Methods of resolving ambiguity of multi-value and mirror are proposed in the process of computing.To the problems of resolution limited by array aperture and large computation cost of algorithms based on fourth-order cumulant, a modified 2-D MUSIC algorithm based on fourth-order cumulant is proposed. According to the theorem that resolution is proportional to array aperture, a group of antennas which constitute the largest virtual aperture is chosen for 2-D direction of arrival estimation, and the new array manifold and construction method of fourth-order cumulant matrix are proposed. The largest virtual array aperture is twice of the actual ones, and its antenna number is the same to the actual ones. According to the new array manifold and fourth-order cumulant matrix, we can realize 2-D direction of arrival estimation following steps of MUSIC algorithm. It prompts resolution validly with limited array aperture and no computation cost in addition. Its availability is testified by simulation experiment.In radar system which is equipped with decoy, usually, the decoy pulse is advanced by radars to protect the radar adequately. According to the receiving characteristic of pulse signals in actual direction finding system, MUSIC algorithm based on some overlap signals is proposed. It can obtain a new covariance matrix of signal by relationships between covariance matrixes of multi-signals and single signal. Then, it can estimate directions of arrival by processing each covariance matrix successively. It testified the feasibility of the proposed algorithm by simulation results and test in actual direction finding system. To solve the problem that the property of spatial spectrum estimation algorithms is sensitive to array channel amplitude-phase mismatch, a real-time calibration method based on self-checking signal is proposed according to the characteristic of actual receiving channel. The whole channel calibration is divided into two parts:the pre-calibration of passive devices between antennas and receiving channels and the real-time calibration of receiving channels. At first, it can get the pre-calibration matrix by setting a signal which has direction of arrival of 0°. Then, it can realize real-time calibration using self-checking signal during the process of direction finding. It is proved by simulation results that the proposed real-time calibration method can dynamically calibrate the channel amplitude-phase mismatch errors and it is helpful to prompt the solve ability of MUSIC algorithm. The experiment in actual direction finding system has also testified that it can calibrate amplitude-phase mismatch real-timely and get higher direction finding precision.According to technical intexes, proposal design, hardware manufacture and test are done to direction finding signal processor. The structure of hardware is introduced in detail, and its software flow chart is also introduced. The computing time of spatial baseline and MUSIC algorithm are test in actual direction finding system. Also, their direction finding accuracy are test in direction finding system. The results of testing in actual system prove that the processor achieve the technical intexes well.