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| 2. |
- Nordebo, Sven, et al.
(författare)
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Sensitivity analysis for antenna near-field imaging
- 2007
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 55:1, s. 94-101
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Tidskriftsartikel (refereegranskat)abstract
- Although imaging and inverse scattering problems have been thoroughly studied during the last century, there is only a partial understanding of these complex problems. Most of the efforts have been placed on the development of efficient inversion algorithms and mathematical uniqueness results. In comparison, there are very few results and a limited knowledge about the information content in the inversion data. In this paper, we provide a mathematical framework for sensitivity analysis of antenna near-field imaging problems, based on the multipole expansion of the electromagnetic field and the Fisher information to quantify the quality of data. By exploiting this framework, a fundamental relation for accuracy and resolution is formulated based on the Cramer-Rao bound (CRB). The sensitivity analysis is illustrated using a relevant example with cylindrical measurement data.
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| 3. |
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| 4. |
- Persson, Kristin, et al.
(författare)
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Experimental validation of reconstructed equivalent currents on a radome
- 2005
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Ingår i: [Host publication title missing]. - 8495999722 ; , s. 35-40
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Konferensbidrag (refereegranskat)abstract
- Knowledge of the current distribution on a radome can be used to improve radome design, detect manufacturing errors, and to verify numerical simulations. In this paper, the transformation from near-field data to its equivalent current distribution on a surface of arbitrary material, ie the radome, is analyzed. The transformation is based on a vector surface integral representation that relates the equivalent currents to the near-field data. Experimental verification using measured near-field data originating from a reflector antenna is then examined. The field irradiates a radome whereupon it is measured on a cylindrical surface. The quantity of data is large since the height of the radome corresponds to 29-43,,wavelengths in the frequency interval 8.0-12.0,,GHz. The presence of axial symmetry enables usage of the fast Fourier transform (FFT) to reduce the computational complexity. Furthermore, the problem is regularized using the singular value decomposition (SVD).
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| 5. |
- Persson, Kristin, et al.
(författare)
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Identification of the current distribution on a radome from near-field measurements
- 2002
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Ingår i: Proceedings radiovetenskap och kommunikation. - 1400-9137. ; , s. 392-395
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Information about the equivalent current distribution on a radome can be used to improve radome design, detect manufacturing errors, and to verify numerical simulations. In this paper, the transformation from near-field data to the equivalent current distribution is analyzed. The transformation is based on a singular value decomposition of the surface integral equation that relates the equivalent current to the near-field data. The attempt is to develop a mathematical model that easily can be used for arbitrary geometric structures. The symmetries of a specific problem is used to reduce the computational complexity. Both synthetic data and measured data are used to verify the algorithm.
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| 6. |
- Persson, Kristin, et al.
(författare)
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Near field to equivalent currents transformation with radome applications
- 2004
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Ingår i: Proceedings International Symposium on Electromagnetic Theory. - 8884922526 ; , s. 1122-1124
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Konferensbidrag (refereegranskat)abstract
- Knowledge about the equivalent currents distribution on a radome can be used to improve radome design, detect manufacturing errors, and to verify numerical simulations. In this paper, the transformation from near-field data to the equivalent currents distribution is analyzed. The transformation is based on a singular value decomposition of the surface integral equation that relates the equivalent currents to the near-field data. The mathematical model can easily be used for arbitrary geometric structures. The symmetries of a specific problem are utilized to reduce the computational complexity. Both synthetic data and measured data are used to verify the algorithm
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| 7. |
- Persson, Kristin, et al.
(författare)
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Radome diagnostics - source reconstruction of phase objects with an equivalent currents approach
- 2014
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 62:4, s. 2041-2051
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Tidskriftsartikel (refereegranskat)abstract
- Radome diagnostics are acquired in the design process, the delivery control, and in performance verification of repaired and newly developed radomes. A measured near or far field may indicate deviations, e.g., increased side-lobe levels, but the origins of the flaws are not revealed. In this paper, radome diagnostics is performed by visualizing the equivalent surface currents on the 3D-radome body, illuminated from the inside. Three different far-field measurement series at 10 GHz are employed. The measured far field is related to the equivalent surface currents on the radome surface by using a surface integral representation. In addition, a surface integral equation is employed to ensure that the sources are located inside the radome. Phase shifts, insertion phase delays (IPD), caused by patches of dielectric tape attached to the radome surface, are localized. Specifically, patches of various edge sizes (0.5-2.0 free-space wavelengths), and with the smallest thickness corresponding to a phase shift of a couple of degrees are imaged.
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| 8. |
- Persson, Kristin, et al.
(författare)
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Radome diagnostics - source reconstruction of phase objects with an equivalent currents approach
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Radome diagnostics are acquired in the design process, the delivery control and in performance verification of repaired and newly developed radomes. A measured near or far field may indicate deviations, e.g., increased side lobe levels, but the origin of the flaws are not revealed. In this paper, radome diagnostic is performed by visualizing equivalent currents on a radome surface. We localize phase shifts, an effective insertion phase delay (IPD), caused by patches of dielectric tape attached to a radome surface. The IPD of one layer tape, 0.15 mm, is detected. Imaging results from three different far-field measurement series at 10 GHz are presented. The measured far field is related to the equivalent surface currents on the radome surface by using a surface integral representation together with the extinction theorem. The problem is solved by a body of revolution method of moment (MoM) code utilizing a singular value decomposition (SVD) for regularization.
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| 9. |
- Persson, Kristin, et al.
(författare)
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Reconstruction and visualization of equivalent currents on a radome using an integral representation formulation
- 2010
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Ingår i: Progress In Electromagnetics Research B. - 1937-6472. ; 20, s. 65-90
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Tidskriftsartikel (refereegranskat)abstract
- In this paper an inverse source problem is investigated. The measurement set-up is a reflector antenna covered by a radome. Equivalent currents are reconstructed on a surface shaped as the radome in order to diagnose the radome's interaction with the radiated field. To tackle this inverse source problem an analysis of a full-wave integral representation, with the equivalent currents as unknowns, is used. The extinction theorem and its associated integral equation ensure that the reconstructed currents represent sources within the radome. The axially symmetric experimental set-up reduces the computational complexity of the problem. The resulting linear system is inverted by using a singular value decomposition. We visualize how the presence of the radome alters the components of the equivalent currents. The method enables us to determine the phase shift of the field due to the transmission of the radome, i.e., the IPD (insertion phase delay). Also, disturbances due to defects, not observable in the measured near field, are localized in the equivalent currents.
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| 10. |
- Persson, Kristin, et al.
(författare)
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Reconstruction of equivalent currents using a near-field data transformation - with radome applications
- 2005
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Ingår i: Progress in Electromagnetics Research-Pier. - 1070-4698. ; 54, s. 179-198
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge of the current distribution on a radome can be used to improve radome design, detect manufacturing errors, and to verify numerical simulations. In this paper, the transformation from near-field data to its equivalent current distribution on a surface of arbitrary material, i. e., the radome, is analyzed. The transformation is based on the scalar surface integral representation that relates the equivalent currents to the near-field data. The presence of axial symmetry enables usage of the fast Fourier transform (FFT) to reduce the computational complexity. Furthermore, the problem is regularized using the singular value decomposition ( SVD). Both synthetic and measured data are used to verify the method. The quantity of data is large since the height of the radome corresponds to 29 - 43wavelengths in the frequency interval 8.0 - 12.0 GHz. It is shown that the method gives an accurate description of the field radiated from an antenna, on a surface enclosing it. Moreover, disturbances introduced by copper plates attached to the radome surface, not localized in the measured near. eld, are focused and detectable in the equivalent currents.
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