Thesis ((PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This dissertation proposes a multi-mode antenna element excited through a multiconductor
feed. It is shown that each of the orthogonal transverse electromagnetic modes supported by
the antenna feed results in a unique radiated far-field pattern that collectively allow for nearhemispherical
field-of-view coverage.
Three multi-mode antenna designs are presented: a dual-mode antenna, integrating a single linearly
polarised dipole antenna with a co-located monopole, as well as two quad-mode antenna
designs integrating two dual-polarised dipole elements with a co-located monopole element.
The dual-mode antenna is excited through a balanced transmission line feed supporting both
differential- and common-mode signals that, respectively, result in typical dipole-over-ground
and monopole radiated far-field patterns. The quad-mode antennas are each fed through a
quadraxial transmission line allowing for excitation through four orthogonal transverse electromagnetic
port modes.
To characterise the multi-mode response of the multi-mode antennas, generalised transformations
are derived by which the multi-mode S-parameters and radiated far-fields can be calculated
from the S-parameters and far-fields corresponding to single-ended excitations. These transformations
are implemented to validate the response of a dual-mode and quad-mode antenna design
through measurements.
An equivalent network representation for active multi-mode antennas is presented, including generalised
transformations relating the multi-mode signal and noise response of the low-noise amplifiers
to the two-port S-parameters and noise parameters of the low-noise amplifiers. Through
the use of classical beamforming algorithms, the performance of an active dual-mode and quadmode
antenna is presented. In the case of the active dual-mode antenna, it is shown that through
the added use of common-mode signals, a variation in sensitivity of less than 50% is achieved
in the E-plane. Similarly, the additional excitation modes supported by the active quad-mode
antenna is shown to result in a significant improvement in the polarimetric capabilities over the
field-of-view coverage. / AFRIKAANSE OPSOMMING: Hierdie proefskrif stel ’n multimodale antenna element voor wat deur ’n multi-geleier transmissielyn
gevoer word. Dit word gewys dat elk van die ortogonale transversale elektromagnetiese
opwekkingsmodusse wat deur die antenna voer ondersteun word, ’n unieke vêrveld stralingspatroon
skep, wat gesamentlik lei tot ’n hemisferiese gesigsveld.
Drie multimodale antenna ontwerpe word voorgestel: ’n dubbelmodale antenna, waarin ’n enkel
lineêrgepolariseerde dipool antenna en monopool mede-geleë word, asook twee viermodale antenna
ontwerpe waarin twee dubbelgepolariseerde dipool elemente geïntegreer word met medegeleë
monopool antenna elemente. Die dubbelmodale antenna word gevoer deur ’n gebalanseerde
transmissielyn wat beide differensiële- en gemene-modus seine ondersteun, waar elk onderskeidelik
dipool-oor-aardvlak en monopool stralingspatrone voortbring. Die viermodale antennas
word elk gevoer deur vier-as transmissielyne wat vier ortogonale transversale elektromagnetiese
opwekkingsmodusse ondersteun.
Om die multimodale gedrag van die drie multimodale antennas te karakteriseer, word veralgemeende
transformasies afgelei waardeur die multimodale strooiingsparameters asook die vêrveld
stralingspatrone vanaf enkelpoort strooiingsparameters en vêrvelde bereken word. Hierdie transformasies
word toegepas om die gedrag van ’n dubbel- en viermodale antenna ontwerp te karakteriseer
deur metings.
Ekwivalente netwerkvoorstellings vir aktiewe multimodale antennas word voorgestel, insluitend
veralgemeende transformasies om die multimodale sein asook ruis gedrag van die lae-ruis versterkers
betreklik te maak tot die tweepoort strooiingsparameters en ruisparameters van die laeruis
versterkers. Deur gebruik te maak van klasieke bundelvormingsalgoritmes, word die gedrag
van aktiewe dubbelmodale en viermodale antennas voorgestel. Vir die aktiewe dubbelmodale
antenna word daar aangedui dat die gesamentlike gebruik van differensiële- en gemene-modus
seine, ’n variasie in sensitiwiteit onder 50% tot gevolg het in die E-vlak. Soortgelyk word daar
aangedui dat die addisionele opwekkingsmodusse wat deur die aktiewe viermodale antenna ondersteun
word, tot ’n beduidende verbetering in die polarisasievermoë oor die gesigsveld lei.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/97008 |
| Date | 03 1900 |
| Creators | Prinsloo, David Schalk Van der Merwe |
| Contributors | Meyer, Petrie, Ivashina, Marianna V., Maaskant, Rob, Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 123 pages : illustrations |
| Rights | Stellenbosch University |
Page generated in 0.002 seconds