@article{ee03bf79ece3471e891b73d1c564c8ba,

title = "A Covariance Approximation Method for Near-Field Direction-Finding Using a Uniform Linear Array",

abstract = "Most narrowband high-resolution bearing estimation algorithms were proposed based on the assumption of a far-field source environment When this assumption is violated, i.e., some sources are in the near field, these algorithms generally provide unsatisfactory performances. In this correspondence, a new algorithm is proposed to handle this near-field problem using a uniform linear array. The received signal covariance matrix for near-field sources is viewed as a corrupted measurement of the ideal signal covariance matrix for far-field sources located at the same bearings. Taking this viewpoint, we reconstruct a far-field approximation (FFA) covariance matrix from the received covariance matrix to reduce the corruptions. Therefore, existing high-resolution bearing estimation techniques can be directly applied to estimate the bearings of the near-field sources. The properties of the proposed approach are investigated in detail. Simulation results demonstrating the effectiveness of this approach are included.",

author = "Lee, {Ju Hong} and Chen, {Yih Min} and Yeh, {Chien Chung}",

note = "Funding Information: This correspondence presents a method to estimate source bearing in the presence of near-field sources using a uniform linear array. The above concept of nonideal sensor is taken for this problem. The proposed method is to reduce the effect of the range-and bearing-dependent complex directional gain pattem of each sensor. The problem being solved is that of using a near-field true covariance to approximate a far-field true covariance. Utilizing the characteristics of the wavefront shape of near-field signals and the signal covariance matrix of incoherent far-field sources, we construct a FFA covariance matrix from the measured covariance matrix to approximate the ideal covariance matrix associated with the far-field signals whose bearings are the same as those of the near-field signals. It is shown that the effect caused by the mismatch between the true phase vector and the assumed far-field phase vector can be alleviated when the FFA covariance matrix is used instead of the original measured covariance matrix. As a result, conventional high-resolution methods can be utilized to estimate the bearings of near-field sources based on the FFA covariance matrix. Moreover, the proposed method does not affect any sources in the far field of the array. Therefore, it can also be employed to deal with the case where some of the signal sources are in the near field, whereas others are in the far field. Theoretical analysis of the relationship between the approximation accuracy of Manuscript received December 29, 1992; October 6, 1994. This work was supported by the National Science Council under Grant NSC84-22 13-EOO2-071. The associate editor coordinating the review of this paper and approving it for publication was Prof. Daniel Fuhrmann.. The authors are with the Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C. IEEE Log Number 9410305.",

year = "1995",

month = may,

doi = "10.1109/78.382421",

language = "???core.languages.en_GB???",

volume = "43",

pages = "1293--1298",

journal = "IEEE Transactions on Signal Processing",

issn = "1053-587X",

number = "5",

}