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Partially Transparent Jaumann-Like Absorber Applied to a Curved Structure
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.ORCID iD: 0000-0001-7269-5241
2011 (English)In: International Journal of Antennas and Propagation, ISSN 1687-5869, 708987- p.Article in journal (Refereed) Published
Abstract [en]

A Jaumann absorber with its metal backing replaced with a combined low-pass and polarizer FSS is investigated with respect to its absorption and its polarization-dependent low-frequency transparency properties. This structure is applied to an idealized curved wing-front end, and its monostatic radar cross-section is determined. The FSS-Jaumann structure preserves an absorption similar to the planar Jaumann absorber in the higher frequency interval and enables a partial transparency in the TE(z) polarization at 1 GHz. In addition, once the structure is applied to the wing-front end, a significant reduction in two-dimensional radar cross-section for both the TM(z) and TE(z) polarization over 2-16 GHz is observed. A sensitivity analysis shows that the resistivity of the inner resistive layer has a large impact on the 1 GHz transmission.

Place, publisher, year, edition, pages
2011. 708987- p.
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-51449DOI: 10.1155/2011/708987ISI: 000296841100001ScopusID: 2-s2.0-81555225224OAI: diva2:464288
QC 20111213Available from: 2011-12-13 Created: 2011-12-12 Last updated: 2012-09-25Bibliographically approved
In thesis
1. Electromagnetic Simulation, Analysis and Design with Application to Antennas and Radar Absorbers
Open this publication in new window or tab >>Electromagnetic Simulation, Analysis and Design with Application to Antennas and Radar Absorbers
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis considers two different subjects in the research area of electromagnetics. The first part is concerned with antenna design and the second with radar absorbers and rasorber.

In the first part, a novel excitation technique for cylindrical dielectric resonator antennas is introduced to produce circular polarization. The exciter is a tape helix that is wound around the dielectric resonator and is fed by a coaxial probe. The helix excites the HE11σ modes in phase quadrature in the cylindrical dielectric resonator antenna. The height of the helix is determined using the Hansen-Woodyard condition for an end-fire array based on the phase velocity of the surface wave traveling along the dielectric resonator side wall. This phase velocity is estimated from the phase velocity in an infinitely long dielectric rod with the same permittivity and radius as the dielectric resonator antenna. The helical exciter is required to operate in the helix axial mode. The height of the helix is usually taller than the height of the dielectric resonator core. Using this type of excitation, a 3 dB axial-ratio bandwidth of 6.4% was achieved for a sample design with dielectric constant εr ~ 11. The achieved 3 dB axial-ratio bandwidth is greater than that typical of other reported single feed cylindrical dielectric resonator antennas. A prototype of the sample design is fabricated and measured and a good agreement between simulation and measurement is observed. Furthermore, two approaches for the enhancement of the 3 dB axial ratio bandwidth are proposed: removing the central portion of the cylindrical dielectric resonator and using stacked cylinders. The advantages and limitations of each approach are discussed. Another perspective on the proposed design is to consider the antenna as a helix with a dielectric resonator core. In this perspective, the effects of the dielectric core on the helix antenna are discussed.

The second part of the thesis is concerned with the design of thin wideband electromagnetic planar absorber for X- and KKu-band which also has a polarization sensitive transparent window at frequencies lower than L-band. The design is based on a two layer capacitive circuit absorber with the backmetal layer replaced with a polarization sensitive frequency selective surface. The structure is studied for normally incident waves with two orthogonal linear polarizations. The structure is optimized to have high transparency at low frequencies for one of the polarizations and at the same time good absorption efficiency for both polarizations at the high-frequency band. For one of the polarizations a -1.9 dB transmission with a transmission loss of less than 10% at 1 GHz as well as a 2.25:1 (75%) bandwidth of -20 dB reflection reduction are achieved. For the other polarization we obtained more than 3:1 (100%) bandwidth of -19 dB absorption. Compared with our earlier design based on a Jaumann absorber, we succeed in significantly reducing the transmission loss at the transparent window. Furthermore, the module of absorption quality is extensively improved. The improvements are based on using periodic arrangements of resistive patches in the structure design. The investigation of the structure for oblique angles of incidence and non-ideal materials is also accomplished.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. ix, 71 p.
Trita-EE, ISSN 1653-5146
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:kth:diva-101477 (URN)978-91-7501-481-4 (ISBN)
Public defence
2012-10-05, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:15 (English)

QC 20120925

Available from: 2012-09-25 Created: 2012-08-29 Last updated: 2012-09-25Bibliographically approved

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Motevasselian, AlirezaJonsson, Lars G.
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