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| 2. |
- Athley, Fredrik, 1968
(författare)
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Asymptotically Decoupled Angle-Frequency Estimation with Sensor Arrays
- 1999
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Ingår i: Proc. 33rd Asilomar Conference on Signals, Systems, and Computers, Pacific Grove, CA, USA.
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the problem of jointly estimating the directions of arrival (DOA) and Doppler frequencies of multiple targets with a pulsed Doppler radar employing an array antenna. This is an application of 2-D frequency estimation. It is shown how the original 2-D estimation problem can be reduced into two 1-D problems. The asymptotic 2-D Cramer-Rao bound (CRB) is derived and compared to the 1-D CRB. It is shown that the DOA bounds are equal for large number of antenna elements. A 1-D/1-D estimator is then presented that achieves the 2-D CRB when the number of temporal snapshots is large. This decoupling of the 2-D problem into sequential 1-D problems leads to a substantial reduction in computational cost without loss of estimation accuracy.
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| 4. |
- Athley, Fredrik, 1968, et al.
(författare)
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High-Resolution Space-Time Signal Processing for Radar
- 2003
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Ingår i: High-Resolution and Robust Signal Processing, To be published, Dekker, editor Y. Hua and A. Gershman and Q. Cheng. - : CRC Press. - 9781482276404
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Athley, Fredrik, 1968
(författare)
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Optimization of Element Positions for Direction Finding with Sparse Arrays
- 2001
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Ingår i: Proc. 11th IEEE Signal Processing Workshop on Statistical Signal Processing, Singapore. - 0780370112 ; , s. 516-519
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Konferensbidrag (refereegranskat)abstract
- Sparse arrays are attractive for Direction-Of-Arrival (DOA) estimation since they can provide accurate estimates at a low cost. A problem of great interest in this matter is to determine the element positions that yield the best DOA estimation performance. A major difficulty with this problem is to define a suitable performance measure to optimize. In this paper, a novel criterion is proposed for optimizing element positions. The ambiguity threshold of the Weiss-Weinstein Bound (WWB) is used to optimize the element positions of a sparse linear array. The array obtained from the optimization is compared with some other sparse array structures that have been proposed in the literature.
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| 6. |
- Athley, Fredrik, 1968
(författare)
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Optimization of element positions for direction finding with sparse arrays
- 2007
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Ingår i: Bayesian Bounds for Parameter Estimation and Nonlinear Filtering/Tracking. - : IEEE. - 9780470544198 ; , s. 545-548
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Sparse arrays are attractive for direction-Of-Arrival (DOA) estimation since they can provideaccurate estimates at a low cost. A problem of great interest in this matter is to determinethe element positions that yield the best DOA estimation performance. A major difficulty with this problem is to define a suitable performance measure to optimize. In this paper, a novel criterion is proposed for optimizing element positions. The ambiguity threshold of the Weiss-Weinstein Bound (WWB) is used to optimize the element positionsof a sparse linear array. The array obtainedfrom the optimization is compared withsome other sparse arraystructuresthat have been proposed in the literature.
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| 7. |
- Athley, Fredrik, 1968
(författare)
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Performance Analysis of DOA Estimation in the Threshold Region
- 2002
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Ingår i: International Conference on Acoustics, Speech, and Signal Processing Location: ORLANDO, FL, MAY 13-17, 2002.
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Konferensbidrag (refereegranskat)abstract
- This paper presents a performance analysis of Maximum Likelihood (ML) Direction-Of-Arrival (DOA) estimation in the threshold region using a sensor array. This region is a range of Signal-to-Noise Ratios (SNR) close to the threshold, where the estimation error due to outliers starts to rise very rapidly as the SNR decreases. Approximate expressions for the probability of outlier and the mean square estimation error are derived for the case of a single signal in white Gaussian noise and a single snapshot. It is verified by simulations that the approximations predict the ML DOA estimation performance with high accuracy also at low SNR where the Cramer-Rao bound is far too optimistic.
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| 8. |
- Athley, Fredrik, 1968
(författare)
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Space-Time Parameter Estimation in Radar Array Processing
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is about estimating parameters using an array of spatially distributed sensors. The material is presented in the context of radar array processing, but the analysis could be of interest in a wide range of applications such as communications, sonar, radio astronomy, seismology, and medical diagnosis. The main theme of the thesis is to analyze the fundamental limitations on estimation performance in sensor array signal processing. To this end, lower bounds on the estimation accuracy as well as the performance of the maximum likelihood (ML) and weighted least-squares (WLS) estimators are studied. The focus in the first part of the thesis is on asymptotic analyses. It deals with the problem of estimating the directions of arrival (DOAs) and Doppler frequencies with a sensor array. This problem can also be viewed as a two-dimensional (2-D) frequency estimation problem. The ML and WLS estimators for this problem amount to multidimensional, highly non-linear optimization problems which would be expensive to solve in real-time in a radar system. Therefore, simplifications of this problem are of great interest. It is shown in this thesis that, under some circumstances, the 2-D problem decouples into 1-D problems. This means a dramatic reduction in computational complexity with insignificant loss of accuracy. The second part contains a performance analysis of the ML DOA estimator under conditions of low signal-to-noise ratio (SNR) and a small number of data samples. It is well known that the ML estimator exhibits a threshold effect, i.e. a rapid deterioration of estimation accuracy below a certain SNR. This effect is caused by outliers and is not captured by standard analysis tools. In this thesis, approximations to the mean square estimation error and probability of outlier are derived that can be used to predict the threshold region performance of the ML estimator with high accuracy. Moreover, these approximations alleviate the need for time-consuming computer simulations when evaluating the ML performance.
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| 9. |
- Athley, Fredrik, 1968
(författare)
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Threshold Region Performance of Deterministic Maximum Likelihood DOA Estimation of Multiple Sources
- 2002
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Ingår i: In Proc. 36th Asilomar Conference on Signals, Systems, and Computers, Pacific Grove, CA, USA, NOV 03-06. ; , s. 1283-1287
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Konferensbidrag (refereegranskat)abstract
- This paper presents an analysis of the threshold region performance of deterministic maximum likelihood direction of arrival estimation using sensor arrays. The threshold effect is caused by outliers and thus is not captured by standard analysis tools such as the Cramer-Rao bound and Taylor expansions, since these are local in nature. The work presented in this paper provides a global analysis that can be used to predict the threshold region performance of the maximum likelihood estimator with high accuracy. It extends previous results from the author on the single source to the multiple sources case.
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