| 21. |
|
|
| 22. |
|
|
| 23. |
- Ludvig-Osipov, Andrei, et al.
(författare)
-
Fundamental bounds on extraordinary transmission with experimental validation
- 2018
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a study of extraordinary transmission (EoT) through arrays of sub-wavelength apertures. Fundamental limitations for this phenomenon are formulated as a sum rule, relating the transmission coefficient over a bandwidth to the static polarizability. The sum rule is rigorously derived for arbitrary periodic apertures in thin screens. By this sum rule we establish a physical bound on the bandwidth of EoT which is verified numerically for a number of aperture array designs. We utilize the sum rule to design and optimize sub-wavelength frequency selective surfaces with a bandwidth close to the physically attainable. Finally, we verify the sum rule and simulations by measurements of an array of horseshoe-shaped slots milled in aluminum foil.
|
|
| 24. |
- Lundgren, Johan, et al.
(författare)
-
IR and Metasurface based mm-Wave Camera
- 2021
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 118
-
Tidskriftsartikel (refereegranskat)abstract
- We have developed a technique to measure low-power electromagnetic fields from mm-wave devices non-intrusively by combining a metasurface, designed to absorb power and focus the radiated power in a thermally isolated region, with an infrared camera. The metasurface consists of thermally isolated elements of low mass and highly emissive material for maximal IR conversion of the incident wave. The IR camera captures the converted energy and indirectly images the incident electromagnetic field on the metasurface. The setup combines multi-scale, multi-physical processes to conduct measurements of the incident electromagnetic fields in real time. In this work, the technique is presented and discussed. Measurements are carried out to demonstrate the technique and image the electromagnetic field of a radiating device. The results compare well with simulations and the technique can measure the low power density levels of consumer devices, as well as provide a general visualization of electromagnetic fields in a live setting.
|
|
| 25. |
- Lundgren, Johan, et al.
(författare)
-
Near-Field Measurement and Calibration Technique for RF EMF Exposure Assessment of mm-wave 5G Devices
- 2019
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Accurate and efficient measurement techniques are needed for exposure assessment of 5G portable devices---which are expected to utilize frequencies beyond 6 GHz---with respect to the radio frequency electromagnetic field exposure limits. Above 6 GHz, these limits are expressed in terms of the incident power density, thus requiring that the electromagnetic fields need to be evaluated with high precision in close vicinity to the device under test (DUT), i.e., in the near-field region of the radiating antenna. This work presents a cutting-edge near-field measurement technique suited for these needs. The technique---based on source reconstruction on a predefined surface representing the radiating aperture of the antenna---requires two sets of measurements; one of the DUT, and one of a small aperture. This second measurement functions as a calibration of both the measurement probe impact on the received signal, and the experimental setup in terms of the relative distance between the probe and the DUT. Results are presented for a 28 GHz and a 60 GHz antenna array; both developed for 5G applications. The computed power density agrees well with simulations at evaluation planes residing as close as one fifth of a wavelength away from the DUT.
|
|
| 26. |
- Nedic, Mitja, et al.
(författare)
-
Herglotz functions and applications in electromagnetics
- 2020
-
Ingår i: Advances in Mathematical Methods for Electromagnetics. - : Institution of Engineering and Technology. - 9781785613845 - 9781785613852 ; , s. 491-514
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Herglotz functions inevitably appear in pure mathematics, mathematical physics, and engineering with a wide range of applications. In particular, they are the pertinent functions to model passive systems, and thus appear in modeling of electromagnetic phenomena in circuits, antennas, materials, and scattering. In this chapter, we review the basic theory of Herglotz functions and its applications to determine sum rules and physical bounds for passive systems.
|
|
| 27. |
- Nordebo, Sven, et al.
(författare)
-
Cylindrical multipole expansion for periodic sources with applications for three-phase power cables
- 2018
-
Ingår i: Mathematical methods in the applied sciences. - : Wiley-Blackwell. - 0170-4214 .- 1099-1476. ; 41:3, s. 959-965
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a c ylindrical multipole expansion for periodic sources with applications for three-phase power cables.It is the aim of the contribution to provide some analytical solutions and techniques that can be useful in the calculation ofcable losses. Explicit analytical results are given for the fields generated by a three-phase helical current distribution andwhich can be computed efficiently as an input to other numerical methods such as, for example , the Method of Moments.It is shown that the field computations are numerically stable at low frequencies (such as 50 Hz) as well as in the quasi-magnetostatic limit provided that sources are divergence-free. The cylindrical multipole expansion is fur thermore usedto derive an efficient analytical model of a measurement coil to measure and estimate the complex valued permeability ofmagnetic steel armour in the presence of a strong skin-effect.
|
|
| 28. |
- Nordebo, Sven, et al.
(författare)
-
Optimal Realizations of Passive Structures
- 2014
-
Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 62:9, s. 4686-4694
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a convex optimization approach to study optimal realizations of passive electromagnetic structures. The optimization approach complements recently developed theory and techniques to derive sum rules and physical limitations for passive systems operating over a given bandwidth. The sum rules are based solely on the analytical properties of the corresponding Herglotz functions. However, the application of sum rules is limited by certain assumptions regarding the low- and high-frequency asymptotic behavior of the system, and the sum rules typically do not give much information towards an optimal realization of the passive system at hand. In contrast, the corresponding convex optimization problem is formulated to explicitly generate a Herglotz function as an optimal realization of the passive structure. The procedure does not require any additional assumptions on the low- and high frequency asymptotic behavior, but additional convex constraints can straightforwardly be incorporated in the formulation. Typical application areas are concerned with antennas, periodic structures, material responses, scattering, absorption, reflection, and extinction. In this paper, we consider three concrete examples regarding dispersion compensation for waveguides, passive metamaterials and passive radar absorbers.
|
|
| 29. |
- Nordebo, Sven, et al.
(författare)
-
Passive approximation and optimization
- 2015
-
Ingår i: Progress in Electromagnetics Research Symposium (PIERS). - 9781934142295 ; , s. 84-
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 30. |
- Regnell, Björn, et al.
(författare)
-
Den osynliga forskargruppen - ledarskap i och kring akademins verksamhetsbärande enheter
- 2010
-
Ingår i: AKKA AKademiska Kollegors Ansvar - Ledarutvecklingsprogram för kvinnor och män vid Lunds universitet 2008-2009. - 9789163363863 ; , s. 99-131
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Denna rapport är slutprodukten av ett projektarbete inom ledarskapsprogrammet AKKA III år 2009 och undersöker den paradoxala situation som uppstår då forskargrupper fungerar som verksamhetsbärande enheter samtidigt som deras formella roll i organisationen är oklar. Detta väcker frågeställningar som är relevanta ur ett ledarskapsperspektiv: Vad är egentligen en forskargrupp? Vilka olika typer av forskargrupper finns det? Vad sker under olika forskargruppers livscykel? Hur ser könssammansättningen ut i de undersökta forskargrupperna? Vilka perspektiv på ledarskapet finns inom och ovanför forskargrupperna? Hur är ledarskap i en forskargruppskontext kopplat till genus och mångfald? Vilka kulturella föreställningar om maskulinitet och femininitet råder i detta ledarskap? Hur beskrivs och synliggörs forskargrupper av universitetet? Hur kan universitet utveckla det omgivande stödet till forskargrupperna så att deras verksamhet kan utvecklas, utan att skapa en alltför tung och kostsam byråkrati? Vi gör inte anspråk på att ge uttömmande svar på alla dessa frågor, men vi har påbörjat en faktabaserad undersökning av ovan nämnda frågeställningar som ligger till grund för den vision som detta arbete mynnar ut i. Visionen kan sammanfattas i följande tre huvudpunkter, som vidare beskrivs och diskuteras i denna rapport: (1) Synliggjorda och erkända forskargrupper (2) Omgivningens goda stöd för en fruktbar livscykel (3) Ledarskap för ett gott forskargruppsklimat
|
|
