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Analysis and Design of Conformal Array Antennas
KTH, Superseded Departments, Electromagnetic Theory.
2002 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Today there is a great need for communication between people and even between things, using systems onboard e.g. aircraft, cars, ships and satellites. As a consequence, these communications needs require antennas mounted on or integrated in the surfaces of different vehicles or platforms, i.e. conformal antennas. In order to ensure proper operation of the communication systems it is important to be able to determine the characteristics of these antennas. This thesis is about the analysis and design of conformal antennas using high frequency asymptotic methods. Commonly used eigenfunction solutions or numerical methods such as FDTD, FEM or MoM are difficult to use for arbitrarily shaped electrically large surfaces. However, the high frequency approximation approach together with an accurate ray tracing procedure offers a convenient solution for these surfaces. The geodesics (ray paths) on the surfaces are key parameters in the analysis and they are discussed in detail. In the first part of the thesis singly and doubly curved perfectly electrical conducting (PEC) surfaces are studied, with respect to the mutual coupling among aperture type elements. A synthesis problem is also considered where the effect of the mutual coupling is taken into account. As expected, the mutual coupling must be included in the synthesis procedure to be able to realize the prescribed pattern, especially in the shaped main lobe. Furthermore, the polarization of the antenna elements is very important when considering antennas on generally shaped surfaces. For such antennas the polarization must most likely be controlled in some way for a proper function. For verification of the results two experimental antennas were built at Ericsson Microwave Systems AB, Mölndal, Sweden. The first antenna is a circular cylinder with an array of rectangular waveguide fed apertures and the second antenna is a doubly curved surface (paraboloid) with circular waveguide fed apertures. It is found that it is possible to obtain very accurate results with the asymptotic method when it is combined with the Method of Moments, i.e. a hybrid method is used. The agreement compared to measurements is good at levels as low as –80 dB in many cases. The second part of the thesis is about the development of a high frequency approximation for surface field calculations on a dielectric covered PEC circular cylinder. When using conformal antennas in practice they have to be covered with a radome for protection and with the method developed here this cover can be included in the analysis. The method is a combination of two different solutions, one valid in the non-paraxial region of the cylinder and the other is valid in the paraxial region. The method is verified against measurements and reference results obtained from a spectral domain moment method code.

Place, publisher, year, edition, pages
Stockholm: KTH , 2002. , xii, 54 p.
Keyword [en]
Conformal antennas, conformal arrays, UTD, high frequency method, MoM, hybrid method, mutual coupling, singly curved surface, doubly curved surface, geodesics, dielectric covered circular cylinder, non-paraxial region. paraxial region, waveguide fed
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-3290ISBN: 91-7283-231-2 (print)OAI: oai:DiVA.org:kth-3290DiVA: diva2:9075
Public defence
2002-01-29, 00:00
Note
QC 20100616Available from: 2002-01-21 Created: 2002-01-21 Last updated: 2010-06-18Bibliographically approved
List of papers
1. Calculating the mutual coupling between apertures on a convex circular cylinder using a hybrid UTD-MoM method
Open this publication in new window or tab >>Calculating the mutual coupling between apertures on a convex circular cylinder using a hybrid UTD-MoM method
2001 (English)In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 0096-1973, Vol. 49, no 4, 672-677 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, the problem of calculating the mutual coupling between apertures on a perfectly conducting circular cylinder is considered. The mutual coupling is calculated by a combination of uniform theory of diffraction (UTD) and the method of moments (MoM). This hybrid method makes it possible to include higher order aperture modes in order to improve the accuracy. It is found that the UTD-MoM solution gives accurate results, even for small cylinders. The results are verified against results found in the literature, as well as against measurements performed at Ericsson Microwave System in Molndal, Sweden. For this purpose, a cylindrical test antenna with 54 apertures was built. Using a single-mode approximation, good agreement down to about -60 dB, comparisons to measured data has been obtained. If additional modes are added the results improve significantly both in amplitude and phase, Zn several cases, the agreement is good down to coupling levels about -80 dB. This requires that about six modes are included. However, the most important mode, besides the fundamental TE10 mode is the TM11 mode.

Keyword
conformal arrays, mutual coupling, UTD/MoM
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13442 (URN)10.1109/8.923330 (DOI)000168640100022 ()
Note
QC 20100618Available from: 2010-06-18 Created: 2010-06-18 Last updated: 2012-06-12Bibliographically approved
2. The Mutual Coupling between Apertures on Convex Cylinders
Open this publication in new window or tab >>The Mutual Coupling between Apertures on Convex Cylinders
1999 (English)In: Proceedings of radiovetenskap och kommunikation / [ed] Jan-Olof Gustafsson, Karlskrona: Högskolan i Karlskrona/Ronneby , 1999Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
Karlskrona: Högskolan i Karlskrona/Ronneby, 1999
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13432 (URN)91-630-8156-3 (ISBN)
Conference
Karlskrona 14-17 juni 1999 / RVK 99
Note
QC 20100618Available from: 2010-06-18 Created: 2010-06-18 Last updated: 2010-06-18Bibliographically approved
3. Conformal array synthesis including mutual coupling
Open this publication in new window or tab >>Conformal array synthesis including mutual coupling
1999 (English)In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 35, no 8, 625-627 p.Article in journal (Refereed) Published
Abstract [en]

A pattern synthesis technique for a conformal array antenna on a cylinder is presented using the method of alternate projections. Both the sidelobe region and the shape of the main beam are controlled. The method includes the effect of the mutual coupling in the synthesis. It is shown that if mutual coupling is neglected, then poor results are obtained, especially in the shaped beam region.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13443 (URN)000080156200013 ()
Note
QC 20100618Available from: 2010-06-18 Created: 2010-06-18 Last updated: 2010-06-18Bibliographically approved
4. Calculating Geodesics on Doubly Curved Surfaces: The case of a General Paraboloid of Revolution
Open this publication in new window or tab >>Calculating Geodesics on Doubly Curved Surfaces: The case of a General Paraboloid of Revolution
2000 (English)Report (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH, 2000
Series
Trita-TET, 00-07
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13433 (URN)
Note
QC 20100618Available from: 2010-06-18 Created: 2010-06-18 Last updated: 2010-06-18Bibliographically approved
5. Investigation of the mutual coupling between apertures on doubly curved convex surfaces: Theory and measurements
Open this publication in new window or tab >>Investigation of the mutual coupling between apertures on doubly curved convex surfaces: Theory and measurements
2003 (English)In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 0096-1973, Vol. 51, no 4, 682-692 p.Article in journal (Refereed) Published
Abstract [en]

A hybrid method of high-frequency approximation (UTD) and method of moments is used to calculate. the mutual coupling between circular apertures on a doubly curved surface. This requires that the geodesics on doubly curved surfaces be found. To represent the aperture fields, a single waveguide mode approximation is used. In order to verify the theoretical results, a general paraboloid of revolution with circular waveguide-fed apertures was built at Ericsson Microwave Systems AB, Molndal, Sweden. This has given a possibility to verify the theoretical model for a general doubly curved surface against measurements. To the authors' knowledge, no such verification is available in the literature. It was found that measured and theoretical results in terms of mutual coupling agree very well for copolar coupling. As expected, the mutual coupling results are very dependent on the polarization. In fact, the definition of polarization directions and the heed for polarization control are important issues for doubly curved conformal array antennas.

Keyword
conformal antenna, double curved surface, geodesics, method of moments (MoM), mutual coupling, uniform theory of diffraction (UTD), RAY ANALYSIS, REVOLUTION, ANTENNAS
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13444 (URN)10.1109/TAP.2003.811101 (DOI)000183931200001 ()
Note
QC 20100618Available from: 2010-06-18 Created: 2010-06-18 Last updated: 2010-06-18Bibliographically approved
6. High-frequency approximation for mutual coupling calculations between apertures on a perfect electric conductor circular cylinder covered with a dielectric layer: Nonparaxial region
Open this publication in new window or tab >>High-frequency approximation for mutual coupling calculations between apertures on a perfect electric conductor circular cylinder covered with a dielectric layer: Nonparaxial region
2003 (English)In: Radio Science, ISSN 0048-6604, E-ISSN 1944-799X, Vol. 38, no 4, 1079- p.Article in journal (Refereed) Published
Abstract [en]

An asymptotic Green's function technique is presented for the calculation of the surface fields on a perfect electric conductor circular cylinder covered with a dielectric layer. The sources are apertures located on the perfect electric conductor surface. This method is very efficient and valid for large cylinders in terms of wavelengths. The new representation is obtained via Watson's transformation and integral contour deformations. The efficiency of the method results from the circumferentially propagating representation of the Green's function as well as the efficient numerical evaluation of various integrals. Numerical results are presented showing good agreement when compared to other solutions as well as measurements.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13436 (URN)10.1029/2002RS002745 (DOI)000185254700001 ()
Note
QC 20100618Available from: 2010-06-18 Created: 2010-06-18 Last updated: 2011-12-15Bibliographically approved
7. A High Frequency Approximation for Mutual Coupling Calculations between Apertures on a PEC Circular Cylinder Covered with a Dielectric Layer Valid in the Paraxial Region: The Gzz case
Open this publication in new window or tab >>A High Frequency Approximation for Mutual Coupling Calculations between Apertures on a PEC Circular Cylinder Covered with a Dielectric Layer Valid in the Paraxial Region: The Gzz case
(English)Manuscript (preprint) (Other academic)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13439 (URN)
Note
QC 20100618Available from: 2010-06-18 Created: 2010-06-18 Last updated: 2010-06-18Bibliographically approved

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