| 11. |
- Ebrahimpouri, Mahsa, et al.
(författare)
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Experimental Validation of a Bespoke Lens for a Slot Log-Spiral Feed
- 2020
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1225 .- 1548-5757. ; 19:4, s. 557-560
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, we experimentally validate the concept of bespoke lenses for the specific design of a log-spiral feed. Bespoke lenses are designed using the concept of quasi-conformal transformation optics (QCTO) to enhance the radiation properties for a given feeding. Our experimental results demonstrate that the antenna with its bespoke lens has higher gain, lower cross polarization, lower sidelobes, and lower axial ratio than that with a conventional hyperhemispherical lens.
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| 12. |
- Ebrahimpouri, Mahsa, et al.
(författare)
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Ultrawideband Anisotropic Glide-Symmetric Metasurfaces
- 2019
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1536-1225 .- 1548-5757. ; 18:8, s. 1547-1551
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Tidskriftsartikel (refereegranskat)abstract
- This letter presents a method to realize anisotropic two-dimensional designs with wideband operation. Glide symmetry has been proven to increase the bandwidth and equivalent refractive index of periodic structures. Here, two anisotropic glide-symmetric unit cells are proposed and characterized. Our simulated results prove that these unit cells follow the general behavior of periodic structures possessing glide symmetry. Moreover, we demonstrate that higher level of anisotropy can also be achieved by glide symmetry. Combining our proposed anisotropic glide-symmetric unit cell and transformation optics, a 30% compressed Luneburg lens is designed. The lens operates from 1 to 13 GHz.
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| 13. |
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| 14. |
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| 15. |
- Frid, Henrik
(författare)
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Closed-Form Relation between the Scan Angle and Feed Position for Extended Hemispherical Lenses based on Ray-Tracing
- 2016
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - : IEEE Press. - 1536-1225 .- 1548-5757. ; 15, s. 1963-1966
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Tidskriftsartikel (refereegranskat)abstract
- This letter presents a closed-form relation between the scan angle and feed position for extended hemispherical lenses. This relation is derived using ray tracing, and it is valid for both large and small scan angles, in excellent agreement with full-wave simulations. It is demonstrated that the relation is linear in the small-angle limit, and the effective focal length determining the scan angle is presented. It is also demonstrated that the scan angle only depends on the geometrical configuration, and that it is independent of the lens material. To demonstrate the applicability of this scan angle relation to the design of focal plane arrays (FPAs), we demonstrate that it can be used to determine the FPA spacing that results in -3-dB overlap between switched beams. A comparison with full-wave simulations of lenses with varying materials and FPA elements demonstrates a root-mean-square (rms) accuracy of 0.27 degrees for the scan angle estimation, and rms accuracy of 0.26 dB for the -3-dB overlap criterion between the central and adjacent beams. Finally, we present scaling rules, which show that the scan resolution is inversely proportional to the lens diameter, whereas the FPA spacing is independent of the total lens size.
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| 16. |
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| 17. |
- Gruden, Mathias, et al.
(författare)
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Measurements and Simulations of Wave Propagation for Wireless Sensor Networks in Jet Engine Turbines
- 2011
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 10, s. 1139-1142
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, measurements and simulations of wave propagation inside a jet engine fan have been performed. The investigation was done using both EM simulations of different cases of propagation inside the engine and by measuring the corresponding cases inside a half-scale model of a jet engine fan. The average path loss was calculated, and the shapes of the fading distributions were extracted. The time between two consecutive fading dips was measured in the empirical part. Measurements were performed with engine speeds of both 30 and 60 rpm and were shown to be linearly scalable from 60 rpm to full speed of 10 000 rpm. The results showed an average path loss of about 55 dB. When scaling the measurements from 60 rpm to full-speed rotation of about 10 000 rpm, the fading was so severe that the time slot between consecutive fading dips was limited to 290 mu s.
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| 18. |
- Gupta, Nitish Kumar, et al.
(författare)
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Singular Phase Characteristics of Electromagnetic Absorbers and a Framework for Low-RCS Target Detection
- 2023
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 22:1, s. 134-138
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Tidskriftsartikel (refereegranskat)abstract
- We conceptualize, numerically validate, and experimentally demonstrate a scheme for distant line-of-sight detection of low-observable targets, such as those covered by metamaterial absorbers, by solely relying on their nontrivial phase characteristics. Relying upon the temporal coupled-mode theory (TCMT), first, we put forward a generalized description of open resonators where we identify the presence of a spectral inflection point in the phase response function as the signature of interest. Thereafter, a realistic phase response function has been modeled and analyzed by incorporating the propagation aspects as well as band-limited Gaussian noise. Change of curvature information owing to the resonant absorption is then ascertained from this involute phase response by developing an algorithm. For pragmatic scrutiny of our proposition, we design a singly resonant (at 12 GHz) wideband resistive sheet-based metamaterial absorber providing − 10 dB absorption across the X- and Ku-bands and employ its de-embedded scattering parameters to confirm the existence of inflection point around 12 GHz. As a final validation, the metamaterial absorber has been fabricated using ITO/PET sheets, and its phase characteristics have been measured in a pseudomonostatic configuration. The information regarding the presence of resonant absorption has been then ascertained by the algorithm extracted phase, thereby validating our proposition.
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| 19. |
- Hallbjörner, Paul, et al.
(författare)
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Broadband Space-Time Measurements in Reverberation Chamber Including Comparison With Real Environment
- 2009
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 8, s. 1111-1114
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Tidskriftsartikel (refereegranskat)abstract
- Spatial variations of the broadband time-domain impulse response in a reverberation chamber are studied experimentally. The goal is to introduce the technique as a means for characterizing reverberation chambers and to demonstrate typical results and the information that can be extracted. Similar measurements are performed in a lab room for comparison. The results provide new insights regarding the signal environment inside a reverberation chamber and how it compares to real-life environments. The minimum number of signal paths in the chamber is calculated based on the spatial and temporal resolutions used in the characterization.
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| 20. |
- Hallbjörner, Paul, et al.
(författare)
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Circularly polarized traveling-wave array antenna with novel microstrip patch element
- 2007
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 6, s. 572-574
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Tidskriftsartikel (refereegranskat)abstract
- A traveling-wave microstrip array antenna with circular polarization in presented. It uses a novel circularly polarized dual-feed radiating element. The element is a square microstrip patch with a chamfered corner. It is fed by microstrip lines, so radiating element and feed lines can be realized in a single layer. A five-element array is designed and built. Measured performance is presented.
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