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Stealth radomes

Poulsen, Sören LU (2006)
Abstract
This dissertation deals with periodic structures that are used as free-space electromagnetic filters. Two types of periodic structures are treated, namely the so called frequency selective surface (FSS) and the artificial puck plate (APP) structure. The FSS structure consists of one or several periodic arrays of identical elements embedded in an arbitrary number of dielectric layers. The APP structure, on the other hand, consists of a thick conducting structure which is perforated with apertures. So called pucks are located in these apertures and an arbitrary number of dielectric layers are attached on either side of the conducting structure.



Free-space electromagnetic filters are used in stealth radome applications... (More)
This dissertation deals with periodic structures that are used as free-space electromagnetic filters. Two types of periodic structures are treated, namely the so called frequency selective surface (FSS) and the artificial puck plate (APP) structure. The FSS structure consists of one or several periodic arrays of identical elements embedded in an arbitrary number of dielectric layers. The APP structure, on the other hand, consists of a thick conducting structure which is perforated with apertures. So called pucks are located in these apertures and an arbitrary number of dielectric layers are attached on either side of the conducting structure.



Free-space electromagnetic filters are used in stealth radome applications where the radome is designed to be transparent within the frequency range of the enclosed antenna, while it is reflective otherwise. By this technique, the radar cross section is reduced which provides the ability to see, but not to be seen. The filters are also used in dichroic reflector antenna applications, where a reflector is either reflective or transparent dependent of the frequency and/or polarisation of the incident field. This technique provides compact antennas with high performance. Furthermore, the filters are also used in the walls of office buildings to prevent the signals transmitted by wireless network devices to leak out of the office building, while the walls still are transparent for mobile phone signals.



Specifically, this dissertation introduces methods for the electromagnetic analysis of the above mentioned filter structures. The method of moments, which is a well known and widely used method for electromagnetic analysis in general, is used to calculate the reflection and transmission properties of the structures, which are assumed to be plane and infinite in two dimensions. Basis functions are used to expand the surface current of the FSS (or the APP). A continuity condition for basis functions used in FSS calculations is derived in the dissertation. The dissertation also presents a new set of so called V-dipole basis functions which can be applied to fairly general FSS element geometries. Moreover, methods that admit complex media to be included in the analysis are presented. This is useful when it comes to glass fibre composites which is an example of a complex media with different properties in different spatial directions. (Less)
Abstract (Swedish)
Popular Abstract in Swedish

Denna avhandling behandlar periodiska strukturer som används som frirymdsfilter för elektromagnetiska vågor. Två typer av periodiska strukturer behandlas, nämligen så kallade frekvensselektiva ytor (FSS) och artificiella puck strukturer (APP). En FSS består av en eller flera periodiska gitter av identiska element som är inbäddade i ett godtyckligt antal dielektriska skikt. En APP består av en tjock ledande struktur som är perforerad med aperturer. Så kallade puckar placeras i dessa aperturer och ett gopdtyckligt antal dielektriska skikt fästs på ömse sidor om den ledande stommen.



Frirymdsfilter för elektromagnetiska vågor används i smygradomtillämpningar där radomen... (More)
Popular Abstract in Swedish

Denna avhandling behandlar periodiska strukturer som används som frirymdsfilter för elektromagnetiska vågor. Två typer av periodiska strukturer behandlas, nämligen så kallade frekvensselektiva ytor (FSS) och artificiella puck strukturer (APP). En FSS består av en eller flera periodiska gitter av identiska element som är inbäddade i ett godtyckligt antal dielektriska skikt. En APP består av en tjock ledande struktur som är perforerad med aperturer. Så kallade puckar placeras i dessa aperturer och ett gopdtyckligt antal dielektriska skikt fästs på ömse sidor om den ledande stommen.



Frirymdsfilter för elektromagnetiska vågor används i smygradomtillämpningar där radomen dimensioneras för att vara transparent inom frekvensområdet hos den omslutna antennen, medan den för övrigt är reflekterande. Med denna teknik reduceras radarmålytan, vilket ger möjlighet att se utan att synas. Elektromagnetiska filter används också i dikroiska reflektorantenntillämpningar, där reflektorn är antingen reflekterande eller transparent beroende på frekvensen och/eller polarisationen hos det infallande fältet. Denna teknik ger antennen ett kompakt format och hög prestanda. Vidare används elektromagnetiska filter också i väggarna i kontorsbyggnader för att förhindra att signaler från trådlösa nätverk läcker ut, samtidigt som de är transparenta för mobiltelefonsignaler.



Avhandlingen presenterar metoder för elektromagnetisk analys av ovan nämnda filterstrukturer. Momentmetoden, som är är en välkänd och etablerad metod för elektromagnetisk analys i allmänhet, används för beräkna reflektions- och transmissionsegenskaperna hos strukturerna, som antas vara plana och oändliga i två riktningar. Basfunktioner används för att utveckla ytströmmen hos FSS- eller APP-strukturen. Ett kontinuitetsvillkor för basfunktionerna som används i FSS-beräkningar presenteras i avhandlingen. Avhandlingen presenterar också en ny uppsättning så kallade V-dipolbasfunktioner som kan tillämpas för tämligen generell geometri hos FSS-elementen. Vidare presenteras metoder som tillå ter att komplexa material inkluderas i analysen. Dessa metoder är användbara för analys av strukturer som innehåller kompositmaterial, vilket är ett exempel på ett komplext material som har olika egenskaper i olika riktningar i rummet. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Vardaxoglou, Yiannis, Loughborough University, United Kingdom
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Electromagnetic scattering, Dichroic structures, Frequency selective surface, Elektroteknik, FSS, Electrical engineering, Radomes
pages
300 pages
publisher
Department of Electroscience, Lund University
defense location
Room E:1406, E-building, Ole Römers väg 3, Faculty of Engineering, Lund University
defense date
2006-06-09 10:15:00
language
English
LU publication?
yes
id
7f90d135-4edc-45dc-bc5f-6e7569c801f3 (old id 546912)
date added to LUP
2016-04-01 16:53:48
date last changed
2018-11-21 20:45:02
@phdthesis{7f90d135-4edc-45dc-bc5f-6e7569c801f3,
  abstract     = {This dissertation deals with periodic structures that are used as free-space electromagnetic filters. Two types of periodic structures are treated, namely the so called frequency selective surface (FSS) and the artificial puck plate (APP) structure. The FSS structure consists of one or several periodic arrays of identical elements embedded in an arbitrary number of dielectric layers. The APP structure, on the other hand, consists of a thick conducting structure which is perforated with apertures. So called pucks are located in these apertures and an arbitrary number of dielectric layers are attached on either side of the conducting structure.<br/><br>
<br/><br>
Free-space electromagnetic filters are used in stealth radome applications where the radome is designed to be transparent within the frequency range of the enclosed antenna, while it is reflective otherwise. By this technique, the radar cross section is reduced which provides the ability to see, but not to be seen. The filters are also used in dichroic reflector antenna applications, where a reflector is either reflective or transparent dependent of the frequency and/or polarisation of the incident field. This technique provides compact antennas with high performance. Furthermore, the filters are also used in the walls of office buildings to prevent the signals transmitted by wireless network devices to leak out of the office building, while the walls still are transparent for mobile phone signals.<br/><br>
<br/><br>
Specifically, this dissertation introduces methods for the electromagnetic analysis of the above mentioned filter structures. The method of moments, which is a well known and widely used method for electromagnetic analysis in general, is used to calculate the reflection and transmission properties of the structures, which are assumed to be plane and infinite in two dimensions. Basis functions are used to expand the surface current of the FSS (or the APP). A continuity condition for basis functions used in FSS calculations is derived in the dissertation. The dissertation also presents a new set of so called V-dipole basis functions which can be applied to fairly general FSS element geometries. Moreover, methods that admit complex media to be included in the analysis are presented. This is useful when it comes to glass fibre composites which is an example of a complex media with different properties in different spatial directions.},
  author       = {Poulsen, Sören},
  language     = {eng},
  publisher    = {Department of Electroscience, Lund University},
  school       = {Lund University},
  title        = {Stealth radomes},
  year         = {2006},
}