The radiation characteristics of microwave antennas using the planar near-field measurement technique

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dc.contributor.advisorCloete, J. H.en_ZA
dc.contributor.advisorPalmer, K. D.en_ZA
dc.contributor.authorBotha, Jeandreen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.en_ZA
dc.date.accessioned2012-08-27T12:27:17Zen_ZA
dc.date.available2012-08-27T12:27:17Zen_ZA
dc.date.issued1992en_ZA
dc.descriptionThesis (MEng) -- University of Stellenbosch, 1992.en_ZA
dc.description.abstractENGLISH ABSTRACT: The thesis with the metrology and diagnosis of microwave antennas using the probe-corrected planar near-field measurement technique. The theoretical formulation of the measurement technique, according to the Plane Wave Scattering Matrix formulation of Kerns was implemented to obtain expressions for the radiation characteristics of an antenna. The representative antenna used in the planar near-field measurements was an 8 x 8 element circularly polarized microstrip antenna array (21. The scan parameters of the antenna was studied and evaluated through planar near-field measurements (31. Results for the representative antenna show that sample spacings up to and a scan length to diameter ratio of 3 or more produce better calculated far-field patterns at a distance of 5 or more from the aperture of the antenna. The on-axis radiation characteristics of three linearly polarized antennas and the circularly polarized antenna array were evaluated with the Friis transmission formulation (4, section 4.21, a modified three-antenna technique 151 as well as the near-field technique. Gain, efficiency and polarization results are presented over 7.5— 12 GHz for the linearly polarized antennas and 7.5—9 GHz for the circularly polarized antenna. Good comparison between the far-field and the near-field technique was attained, considering the encountered error. Two-dimensional planar near-field measurement; were conducted on the circularly polarized antenna and a pyramidal horn antenna to evaluate and compare their far-field patterns with conventionally measured far-field pattern principal cuts. The far field patterns were with and without probe correction and the probe-corrected patterns were found to predict the measured far-field cuts better than those calculated without probe correction. The backward transform process was used to predict the reconstructed aperture distributions of these antennas. The aperture distribution of the pyramidal horn antenna compared very well with theoretically predicted distribution. A survey was performed obtain enhanced resolution for the circularly polarized antenna. These results show that the scan parameters play vital in the achievable resolution and that sources in an array antenna, closer than approximately A/2 from each other, were not resolvable. en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Die meet parameters van die antenne was bestudeer en geévalueer met behulp van planére nabyvcld metings (31. Resultate, vir die verteenwoordigende antenne, toon dat mon- sterspasiérings of kleiner mag wees en dat die verhouding van die meetlcngte tot die diameter van die antenne, 3 of meer kan wees, vir aanvaarbare fouttoleransies in die berekende verveld op 'n afstand van 5A of meer vanaf die antenne oppervlak. Die hoof-as stralingseienskappe van drie lineér-gepolariseerde antennes en die sirkel-gepola- riseerde antenne was geévalueer met behulp van die Friis transmissie formulering [4 seksie 4.2], 'n gemodifiseerde drieantenne tegniek [51 sowel as die nabyveld tegniek. Aanwins, benuttingsgraad er polarisasie eienskappe van die antennes was geévalueer oor 7.5 — 9 GHz vir die sirke:-gepolariseerde antenne en 7.5 — 12 GHz vir die lineér-gepolariseerde antennes. Goeie ooreenkoms tussen die verveld en die nabyveld tegnieke was verkry, met inagneming van die geidentifiseerde foutbronne. Twee-dimensionele planére nabyveld metings was verkry vir die sirkel-gepolariseerde antenne en 'n piramidale hor:rg antenne om sodoende hul verveld met konvensioneel gemete verveld resultate te vergelyk. Die verveld was bereken, rnet en sonder probe korreksie. Die probe-gekorrigeerde verveld het beter ooreenkoms met die geme,e verveld getoon. Die rekonstruksie van die antenne oppervlak distribusie was 00k ondersoek deur gebruik te maak van 'n terug-transformasie proses in die nabyveld tegniek. Die oppervlak verspreiding van die horing antenne het baie goed ooteengestein met algemeen aanvaarde teoretiese uitdrukkings vir die oppervlak verspreiding. Ondersoek was verder gevoer na verhoogde resolusie moontlikhede, deur gebruik te maak van die sirkel-gepolariseerde antenne samestelling. Resultate wys dat die meet parameters 'n groot rol speel in die bereikbare resolusie. Bronne, op die oppervlak van 'n samotelling, met spasiérings kleiner as ongeveer A/2, was nie onderskeibaar nie. af_ZA
dc.format.extent140 pages : illustrationsen_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/69813en_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshMicrowave antennas -- Measurementen_ZA
dc.subject.lcshRadiationen_ZA
dc.subject.lcshMetrologyen_ZA
dc.subject.lcshUCTDen_ZA
dc.titleThe radiation characteristics of microwave antennas using the planar near-field measurement techniqueen_ZA
dc.typeThesisen_ZA
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