| 211. |
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| 212. |
- Nordebo, Sven, et al.
(author)
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Fundamental limitations for DOA and polarization estimation with applications in array signal processing
- 2006
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In: IEEE Transactions on Signal Processing. - 1053-587X. ; 54:10, s. 4055-4061
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Journal article (peer-reviewed)abstract
- Using a generic electromagnetic model based on the spherical vector harmonics, we provide the Cramer-Rao lower bound (CRB) for direction-on-arrival (DOA) and polarization estimation with arbitrary multiport antennas. By reciprocity, the receiving multiport antenna is characterized in terms of the transmission matrix from incident voltage waves to multipole coefficients of the outgoing spherical vector waves. Explicit results of the CRB for the Gaussian case is given in terms of the transmission matrix, the spherical vector harmonics and its spatial derivatives. Numerical examples are included to illustrate the results.
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| 213. |
- Nordebo, Sven, et al.
(author)
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Fundamental Limitations for DOA Estimation by a Sphere
- 2004
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Reports (other academic/artistic)abstract
- In this paper we consider fundamental limitations for DOA estimation with arbitrary lossless antennas or antenna arrays inserted inside a sphere. Spherical vector modes and their associated equivalent circuits and Q factor approximations are employed as a general framework for the analysis. The classical broadband matching theory by Fano is extended to a general multiport S–parameter model of the antennas and fundamental bounds are given for the scattering parameters with respect to bandwidth and electrical size of the sphere. Finally, assuming a statistical signal model with Gaussian receiver noise, the Cramer–Rao lower bound is used to derive fundamental upper bounds for the performance of DOA estimation by a sphere.
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| 214. |
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| 215. |
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| 216. |
- Nordebo, Sven, et al.
(author)
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Low-frequency dispersion characteristics of a multilayered coaxial cable
- 2013
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In: Journal of Engineering Mathematics. - : Springer Netherlands. - 0022-0833 .- 1573-2703. ; 83:1, s. 169-184
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Journal article (peer-reviewed)abstract
- This paper provides an exact asymptotic analysis regarding the low-frequency dispersion characteristics of a multilayered coaxial cable. A layer-recursive description of the dispersion function is derived that is well suited for asymptotic analysis. The recursion is based on two well-behaved (meromorphic) subdeterminants defined by a perfectly electrically conducting (PEC) and a perfectly magnetically conducting termination, respectively. For an open waveguide structure, the dispersion function is a combination of two such functions, and there is only one branch point that is related to the exterior domain. It is shown that if there is one isolating layer and a PEC outer shield, then the classical Weierstrass preparation theorem can be used to prove that the low-frequency behavior of the propagation constant is governed by the square root of the complex frequency, and an exact analytical expression for the dominating term of the asymptotic expansion is derived. It is furthermore shown that the same asymptotic expansion is valid to its lowest order even if the outer shield has finite conductivity and there is an infinite exterior region with finite nonzero conductivity. As a practical application of the theory, a high-voltage direct current (HVDC) power cable is analyzed and a numerical solution to the dispersion relation is validated by comparisons with the asymptotic analysis. The comparison reveals that the low-frequency dispersion characteristics of the power cable is very complicated and a first-order asymptotic approximation is valid only at extremely low frequencies (below 1 Hz). It is noted that the only way to come to this conclusion is to actually perform the asymptotic analysis. Hence, for practical modeling purposes, such as with fault localization, an accurate numerical solution to the dispersion relation is necessary and the asymptotic analysis is useful as a validation tool.
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| 217. |
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| 218. |
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| 219. |
- Nordebo, Sven, et al.
(author)
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Minimum Norm Design of Two-Dimensional Weighted Chebyshev FIR Filters
- 1997
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In: IEEE transactions on circuits and systems. 2, Analog and digital signal processing (Print). - New York : IEEE Circuits and Systems Society. - 1057-7130 .- 1558-125X. ; 44:3, s. 251-253
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Journal article (peer-reviewed)abstract
- The weighted Chebyshev design of two-dimensional FIR filters is in general not unique since the Haar condition is not generally satisfied. However, fo r a design on a discrete frequency domain, the Haar condition might be fulf illed. The question of uniqueness is, however, rather extensive to investig ate. It is therefore desirable to define some simple additional constraints to the Chebyshev design in order to obtain a unique solution. The weighted Chebyshev solution of minimum Euclidean filter weight norm is always uniqu e, and represents a sensible additional constraint since it implies minimum white noise amplification. This unique Chebyshev solution can always be ob tained by using an efficient quadratic programming formulation with a stric tly convex objective function and linear constraints. An example where a co nventional Chebyshev solution is nonunique is discussed in the brief.
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| 220. |
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