Design and Analysis of Nonmagnetic Specular Radar Absorbing Materials
Author
Summary, in English
The dissertation is composed of six peer-reviewed papers. A new versatile design method is proposed in the first paper with outstanding capabilities and remarkable applications. The method is named ''capacitive circuit absorber'' (CCA) and is demonstrated with different design examples to verify its superiority in comparison to the other design approaches. For example, the possibility of utilizing high permittivity dielectric spacers in conjunction with frequency selective surfaces (FSS) in wideband designs is illustrated. The second paper deals with ultra thin absorbers. Recently different proposals based on meta-materials or electromagnetic band-gap structures were suggested for low profile absorbers. The thesis shows that the absorption mechanisms in ultra thin structures are due to excitation of longitude electric field component and no meta-material effect is involved in the absorption process. It is demonstrated that TM cavity modes of patch antennas can approximate fairly accurately the absorption frequency in both periodic and finite extent absorbers. The design of multilayered Jaumann and FSS based absorbers for large scan angles are presented in the third paper. The possibility of extension of the scan and frequency compensation techniques, formerly formulated for single resistive layer designs, to multilayered absorbers is illustrated. It is shown that in contrast to single resistive layer designs, there are some degrees of freedom in the selection of the dielectric layers. Design of ultra wideband absorbers, bandwidth ratios in order of 10:1, with optimal thickness is studied in the fourth paper. It is shown that for achieving an ultra wideband design with optimal thickness, utilization of different spatial periodicities for the periodic layers is essential. By the aid of the physical bound for absorbers it is verified that our design approach leads to optimal total thicknesses. Design of thin wideband absorbers is the topic of the fifth paper, where the challenging problem of reasonable tradeoff between bandwidth and thickness is addressed. The effect of mutual coupling between periodic layers and the ground plane on the frequency response of a thin design is investigated and practical methods for minimizing the couplings are introduced. A thin design is proposed for the X-band which has a total thickness very close to the theoretical limit. Finally in the last paper the physical bound on the absorbers, originally published for normal angle of incidence, is extended to arbitrary angle of incidence for different polarizations. Applicability of the new bounds is examined with different design examples.
Publishing year
2010
Language
English
Document type
Dissertation
Publisher
Department of Electrical and Information Technology, Lund University
Topic
- Electrical Engineering, Electronic Engineering, Information Engineering
Status
Published
Research group
- Electromagnetic theory
Supervisor
ISBN/ISSN/Other
- ISBN: 978-91-628-8105-4
Defence date
27 May 2010
Defence time
10:15
Defence place
Lecture Hall E:1406, Department of Electrical and Information Technology, Lund University Faculty of Engineering
Opponent
- Kenneth Lee Ford (Dr.)