| 31. |
- Nordebo, Sven, et al.
(author)
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On the Capacity of the Free Space Antenna Channel
- 2006
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In: IEEE Antennas and Propagation Society International Symposium. - 1424401232 ; , s. 3105-3108
-
Conference paper (peer-reviewed)abstract
- This paper investigates the fundamental free-space antenna translation channel as an important step in understanding and developing the spherical waves as a generic tool for MIMO channel modeling. The model is demonstrated by quantifying the theoretical MIMO capacity associated with antennas exciting high order modes in the Fresnel and Fraunhofer regions.
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| 32. |
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| 33. |
- Nordebo, Sven, et al.
(author)
-
On the relation between optimal wideband matching and scattering of spherical waves
- 2011
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In: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 59:9, s. 3358-3369
-
Journal article (peer-reviewed)abstract
- Abstract in UndeterminedUsing an exact circuit analogy for the scattering ofvector spherical waves, it is shown how the problem of determiningthe optimal scattering bounds for a homogeneous spherein its high-contrast limit is identical to the closely related, andyet very different problem of finding the broadband tuning limitsof the spherical waves. Using integral relations similar to Fano’sbroadband matching bounds, the optimal scattering limitationsare determined by the static response as well as the high-frequencyasymptotics of the reflection coefficient. The scattering view of thematching problem yields explicitly the necessary low-frequencyasymptotics of the reflection coefficient that is used with Fano’sbroadband matching bounds for spherical waves, something thatappears to be non-trivial to derive from the classical networkpoint of view.
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| 34. |
- Nordebo, Sven, et al.
(author)
-
On the relation between optimal wideband matching and scattering of spherical waves
- 2010
-
Reports (other academic/artistic)abstract
- Using an exact circuit analogy for the scattering of vector spherical waves, it is shown how the problem of determining the optimal scattering bounds for a homogeneous sphere in its high-contrast limit is identical to the closely related, and yet very different problem of finding the broadband tuning limits of the spherical waves. Using integral relations similar to Fano's broadband matching bounds, the optimal scattering limitations are determined by the static response as well as the high-frequency asymptotics of the reflection coefficient. The scattering view of the matching problem yields explicitly the necessary low-frequency asymptotics of the reflection coefficient that is used with Fano's broadband matching bounds for spherical waves, something that appears to be non-trivial to derive from the classical network point of view.
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| 35. |
- Persson, Kristin, et al.
(author)
-
Experimental validation of reconstructed equivalent currents on a radome
- 2005
-
In: [Host publication title missing]. - 8495999722 ; , s. 35-40
-
Conference paper (peer-reviewed)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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| 36. |
- Persson, Kristin, et al.
(author)
-
Radome diagnostics - source reconstruction of phase objects with an equivalent currents approach
- 2014
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In: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 62:4, s. 2041-2051
-
Journal article (peer-reviewed)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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| 37. |
- Persson, Kristin, et al.
(author)
-
Radome diagnostics - source reconstruction of phase objects with an equivalent currents approach
- 2012
-
Reports (other academic/artistic)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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| 38. |
- Persson, Kristin, et al.
(author)
-
Reconstruction and visualization of equivalent currents on a radome using an integral representation formulation
- 2010
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In: Progress In Electromagnetics Research B. - 1937-6472. ; 20, s. 65-90
-
Journal article (peer-reviewed)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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| 39. |
- Persson, Kristin, et al.
(author)
-
Reconstruction of Equivalent Currents Using a Near-Field Data Transformation - with Radome Applications
- 2004
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In: Proceedings EMB04. - 9163160765 ; , s. 124-131
-
Conference paper (other academic/artistic)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, ie the radome, is analyzed. The transformation is based on the surface integral representation that relates the equivalent currents to the near-field data. The full vector formulation is used in the analyzis but the numerical results are limited to the scalar approximation. It is shown that defects on the radome, not localized in the measured near field, are focused and detectable on the radome surface.
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| 40. |
- Persson, Kristin, et al.
(author)
-
Source reconstruction by far-field data for imaging of defects in frequency selective radomes
- 2013
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In: IEEE Antennas and Wireless Propagation Letters. - 1548-5757. ; 12, s. 480-483
-
Journal article (peer-reviewed)abstract
- In this paper, an inverse source reconstruction method with great potential in radome diagnostics is presented. Defects, e.g., seams in large radomes, and lattice dislocations in frequency selective surface (FSS) radomes, are inevitable, and their electrical effects demand analysis. Here, defects in a frequency selective radome are analyzed with a method based on an integral formulation. Several far-field measurement series, illuminating different parts of the radome wall at 9.35 GHz, are employed to determine the equivalent surface currents and image the disturbances on the radome surface.
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