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dc.contributor.authorWeeratumanoon, Eakasiten_US
dc.date.accessioned2014-03-14T20:31:40Z
dc.date.available2014-03-14T20:31:40Z
dc.date.issued2000-01-27en_US
dc.identifier.otheretd-02102000-19330046en_US
dc.identifier.urihttp://hdl.handle.net/10919/31193
dc.description.abstractA new variation of the spherical helical antenna made of a wire wound over a hemispherical surface and backed by a conducting ground plane is introduced. A constant spacing is maintained between the turns of winding. The geometry of this antenna is fully described by the number of turns and the radius of hemispherical surface. In addition to the hemispherical geometry, truncated double spherical helices are also examined. Radiation properties of the proposed antennas are studied both theoretically and experimentally. The wire antenna code ESP (electromagnetic surface patch), which is based on the method of moments, is used to obtain simulation results. The results for far-field patterns, gain, axial ratio, bandwidth, and input impedance are presented. Several prototypes of this antenna were constructed and tested using an outdoor antenna range. Far-field patterns were measured over a wide range of frequencies. The measured and calculated radiation patterns are in good agreement.

A unique property of the hemispherical helix is its broad half-power beamwidth. Furthermore, this antenna provides circular polarization and relatively high gain over a narrow frequency range. The results of this research show that, for example, a 4.5-turn hemispherical helix with a radius of 0.02 meter designed for operation around 2.8 GHz provides a half-power beamwidth of about 90 degrees, more than 9 dB gain, and less than 3 dB axial ratio over a 300 MHz bandwidth. The input impedance of the antenna is largely resistive and is about 150 ohms in the above frequency range. Compared with a full spherical helix, the hemispherical helix provides comparable radiation characteristics, but occupies only half the volume. The compact size of this antenna makes it attractive to mobile communication applications

en_US
dc.publisherVirginia Techen_US
dc.relation.haspart13appendixA.PDFen_US
dc.relation.haspart10chapter5.PDFen_US
dc.relation.haspart01title1.PDFen_US
dc.relation.haspart06chapter1.PDFen_US
dc.relation.haspart05title5.PDFen_US
dc.relation.haspart09chapter4.PDFen_US
dc.relation.haspart02title2.PDFen_US
dc.relation.haspart11chapter6.PDFen_US
dc.relation.haspart17vita.PDFen_US
dc.relation.haspart04title4.PDFen_US
dc.relation.haspart12reference.PDFen_US
dc.relation.haspart16appendixD.PDFen_US
dc.relation.haspart08chapter3.PDFen_US
dc.relation.haspart07chapter2.PDFen_US
dc.relation.haspart14appendixB.PDFen_US
dc.relation.haspart03title3.PDFen_US
dc.relation.haspart15appendixC.PDFen_US
dc.rightsI hereby grant to Virginia Tech or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University Libraries in all forms of media, now or hereafter known. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation.en_US
dc.subjectSpherical Helixen_US
dc.subjectWire Antennasen_US
dc.subjectHelical Antennaen_US
dc.titleHelical Antennas with Truncated Spherical Geometryen_US
dc.typeThesisen_US
dc.contributor.departmentElectrical and Computer Engineeringen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.levelmastersen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
dc.contributor.committeechairSafaai-Jazi, Ahmaden_US
dc.contributor.committeememberBesieris, Ioannis M.en_US
dc.contributor.committeememberStutzman, Warren L.en_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-02102000-19330046/en_US
dc.date.sdate2000-02-10en_US
dc.date.rdate2001-02-16
dc.date.adate2000-02-16en_US


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