Miniaturized Hard Waveguides in Multifunction Array Antennas (PhD Thesis) (Record no. 351130)

MARC details
000 -LEADER
fixed length control field 05819nam a2200217Ia 4500
008 - FIXED-LENGTH DATA ELEMENTS--GENERAL INFORMATION
fixed length control field 070903s2005||||xx |||||||||||||| ||eng||
020 ## - INTERNATIONAL STANDARD BOOK NUMBER
International Standard Book Number 9172917016
022 ## - INTERNATIONAL STANDARD SERIAL NUMBER
ISSN-L 91-7291-701-6
041 ## - LANGUAGE CODE
Language code of text/sound track or separate title English
082 ## - DEWEY DECIMAL CLASSIFICATION NUMBER
Classification number 621.3824378242
Item number KEH
100 ## - MAIN ENTRY--PERSONAL NAME
Relator term author
Personal name Kehn, Malcolm Ng Mou
9 (RLIN) 98889
245 #0 - TITLE STATEMENT
Title Miniaturized Hard Waveguides in Multifunction Array Antennas (PhD Thesis)
260 ## - PUBLICATION, DISTRIBUTION, ETC.
Place of publication, distribution, etc. Goteborg, Sweden :
Name of publisher, distributor, etc. Chalmers University of Technology Department of Signals and Systems Antenna Group,
Date of publication, distribution, etc. c2005
300 ## - PHYSICAL DESCRIPTION
Extent X, vp.
Other physical details : ill
504 ## - BIBLIOGRAPHY, ETC. NOTE
Bibliography, etc. note Includes Bibliographical References
520 ## - SUMMARY, ETC.
Summary, etc. Abstract:<br/><br/>Recent advances in technologies of wireless communications systems have led to an increasing desire for several antennas performing diverse functions at different frequencies to be integrated into a common radiating aperture. This gives rise to the so-called multifunction antenna, which affords the saving of scarce premium real estate and can alleviate problems arising from excessive antenna protrusions in aspects such as aerodynamics, aesthetics, and stealth capability in military applications. Where rapid and simultaneous operations are required, electronically phased-steered array antennas using waveguide elements offer an effective and viable solution. This is in virtue of the excellent isolation which waveguides can provide when operated below the fundamental modal cutoff. Miniaturized waveguide elements are thus needed for realizing multi-frequency interlaced arrays. Although to entirely fill waveguides with dielectric material to realize compact waveguides is feasible, the increased attenuation losses and weight may cause problems. An alternative approach is the partially-filled sidewall loaded rectangular waveguide. The advantages of this waveguide include having lower dielectric losses and being lighter than its entirely filled counterpart. These advantages, however, are still trivial. The prominent property which this alternative waveguide possess is that when operated at the so-called TEM frequency, the fundamental mode of this structure displays TEM plane wave properties, i.e. uniform aperture field distribution over the empty region with clean linear polarization, and exhibiting a modal propagation constant that is equal to that of a uniform plane wave in free space. Therefore, these are called quasi-TEM hard waveguides. Intuitively, these attributes may provide good radiation performance when the waveguides are terminated as open-ended radiating elemental apertures of a planar array antenna. However, they may be advantageous only for broadside array scan and when the radiating aperture entirely fills the unit cell. The latter aspect is certainly violated in interlaced arrays requiring miniaturized waveguide elements. It is then a primary objective of this thesis to investigate the complete and true effects of the TEM modal plane wave property of the hard waveguide elements on the array performance. Results have shown that, even when operated at the TEM condition under broadside array scan, miniaturized apertures of the quasi-TEM hard waveguides lead to poor array transmission. Nevertheless, miniaturization in E-plane is found to be more facilitated than in H-plane. The performance at the TEM condition is optimal for a particular aperture size, this being a crucial finding. When an internal homogeneous dielectric layer is incorporated into each waveguide element to serve as a matching section, very good array transmission can be obtained even for highly miniaturized apertures under a specific set of operating conditions, e.g. matched for broadside array scan and at the TEM frequency. However, the matching is narrowband. Nonetheless, this provides good isolation from other frequencies and allows closely separated bands to be operated simultaneously. Moreover, the matching is fairly well maintained even when the array is scanned off broadside in both principal E and H planes. It is also learnt that the bandwidth of the matching degrades more rapidly when the aperture is miniaturized in H-plane than in E-plane.<br/> Although the waveguide elements of the array operating at the lower frequency band are unable to interfere with those of the higher frequency bands, the converse is not true. <br/>This may be solved if the waveguides of the lower frequency band have, in addition to a usual lower cutoff frequency, an upper one as well. Novel waveguides with such a feature can be realized by loading the internal walls with metamaterials. This thesis has studied one such structure comprising an array of metallic strip dipoles imprinted on the surfaces of the two dielectric sidewall loadings of a rectangular waveguide. This structure serves as a waveguide filter, displaying a passband within which the lower frequency band can be operated, and an upper stopband in which the higher frequency band may reside. <br/>The thesis concludes with a final investigation on the prospect of using an array of open-ended waveguide apertures as a focal plane array feed for reflector antennas. The goal of the study was to ascertain the effects of mutual coupling on radiation efficiency. Although an active uniformly illuminated and linearly phase steered array only has reflection losses but no coupled losses, an array feed whose aperture is synthesized to match the focal plane fields of a reflector antenna has both reflection and coupled losses. Hence, although a desired feed radiation pattern may be synthesized to achieve high feed efficiency, the radiation efficiency has often been neglected. This work elucidates the importance of the latter aspect.<br/>
650 #0 - SUBJECT ADDED ENTRY--TOPICAL TERM
Topical term or geographic name entry element Array Antennas Thesis
9 (RLIN) 882843
650 #0 - SUBJECT ADDED ENTRY--TOPICAL TERM
Topical term or geographic name entry element Focal Panel Array Thesis
9 (RLIN) 882844
856 ## - ELECTRONIC LOCATION AND ACCESS
Link text Table of Contents
Uniform Resource Identifier <a href="https://eaklibrary.neduet.edu.pk:8443/catalog/bk/books/toc/91-7291-701-6.pdf">https://eaklibrary.neduet.edu.pk:8443/catalog/bk/books/toc/91-7291-701-6.pdf</a>
942 ## - ADDED ENTRY ELEMENTS (KOHA)
Koha item type PHD Thesis
Source of classification or shelving scheme Dewey Decimal Classification
Holdings
Withdrawn status Lost status Source of classification or shelving scheme Damaged status Not for loan Home library Current library Shelving location Date acquired Stock Type Total Checkouts Full call number Barcode Date last seen Accession Date Koha item type
    Dewey Decimal Classification     Government Document Section Government Document Section Govt Publication Section 20/10/2022 Donation   621.3824378242 KEH 76694 06/03/2024 03/09/2007 Reference Collection
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