Abstract
Sources with large power differences are very common, especially in complex electromagnetic environments. Classical DOA estimation methods suffer from performance degradation in terms of resolution when dealing with sources that have large power differences. In this paper, we propose an improved DOA algorithm to increase the resolution performance in resolving such sources. The proposed method takes advantage of diagonal loading and demonstrates that the invariant property of noise subspace still holds after diagonal loading is performed. We also find that the Cramer–Rao bound of the weak source can be affected by the power of the strong source, and this has not been noted before. The Cramer–Rao bound of the weak source deteriorates as the power of the strong source increases. Numerical results indicate that the improved algorithm increases the probability of resolution while maintaining the estimation accuracy and computational complexity.
Highlights
Direction-of-arrival (DOA) estimation has been extensively investigated due to its wide applications in radar, sonar, wireless communication, and navigation [1,2,3,4]; e.g., DOA estimation is of significance for source location in MIMO radar [5], and the issue of DOA estimation for noncircular sources is valuable in practical communications [6]
With prior DOA knowledge of the strong interference, the interference jamming method (IJM) is proposed in [14], where strong interferences are eliminated by transforming the M × Ndimensional array manifold matrix into M × (N − j) dimensions, in which M is the number of array elements, N is the number of incident sources, and j is the number of strong interferences
We propose an improved DOA estimation algorithm to increase the resolution performance based on the invariant property of noise subspace (IPNS). e improved algorithm takes advantage of diagonal loading, and we demonstrate that the IPNS still holds after diagonal loading. e Cramer-Rao bound (CRB) of the weak source is studied in the presence of a strong source to examine the influence caused by the power of the strong source. e numerical results indicate that our approach is highly effective in solving two closely spaced sources with large power differences. e rest of this paper is organized as follows
Summary
Direction-of-arrival (DOA) estimation has been extensively investigated due to its wide applications in radar, sonar, wireless communication, and navigation [1,2,3,4]; e.g., DOA estimation is of significance for source location in MIMO radar [5], and the issue of DOA estimation for noncircular sources is valuable in practical communications [6]. E other type of DOA estimation method for sources with power differences does not need prior knowledge This type mostly employs numerous iterations at the cost of increased computational complexity. A robust orthogonal projection method based on an optimized sparse array is proposed without prior knowledge in which the DOAs of strong and weak targets are precisely estimated [26], but many iterations are still needed. Both iterations and prior knowledge are not required for the DOA estimation algorithm, which utilizes the invariant property of noise subspace (IPNS) [27, 28].
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