{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/36060"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/36060","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Multifilar Hemispherical Helical Antennas","abstract":"Helices are broadband antennas that provide moderate gain, largely real input impedance and circular polarization when operating in the axial mode regime. A modified form of the helix, the spherical helix, has been shown to yield similar polarization and gain characteristics over a narrow bandwidth but a much larger beamwidth. This investigation examines multifilar hemispherical helices and produces two specific designs with some desirable radiation characteristics. The side-fed quadrifilar helix and the top-fed bifilar helix are the new hemispherical designs which are studied in detail both numerically and experimentally. The Numerical Electromagnetics Code 4 is used to analyze the radiation characteristics of the proposed multifilar hemispherical helices. Directivity, E- and H-plane radiation patterns, axial ratio and input impedance of a few example designs are calculated. Measurements, taken in the anechoic chamber at the Virginia Tech antenna range, generally confirmed the simulation results. It is shown that the bifilar hemispherical helix provides a flat gain curve over the measured bandwidth (~14%) and generally elliptical polarization with near circular polarization in limited case.","abstract_html":"Helices are broadband antennas that provide moderate gain, largely real input impedance and circular polarization when operating in the axial mode regime. A modified form of the helix, the spherical helix, has been shown to yield similar polarization and gain characteristics over a narrow bandwidth but a much larger beamwidth. This investigation examines multifilar hemispherical helices and produces two specific designs with some desirable radiation characteristics. The side-fed quadrifilar helix and the top-fed bifilar helix are the new hemispherical designs which are studied in detail both numerically and experimentally. The Numerical Electromagnetics Code 4 is used to analyze the radiation characteristics of the proposed multifilar hemispherical helices. Directivity, E- and H-plane radiation patterns, axial ratio and input impedance of a few example designs are calculated. Measurements, taken in the anechoic chamber at the Virginia Tech antenna range, generally confirmed the simulation results. It is shown that the bifilar hemispherical helix provides a flat gain curve over the measured bandwidth (~14%) and generally elliptical polarization with near circular polarization in limited case.","abstract_has_math":false,"creators":["Clark, Jeffrey R."],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Electrical and Computer Engineering","degree_department":"Electrical and Computer Engineering","school":null,"contributors":[],"advisors":[],"committee_chairs":["Safaai-Jazi, Ahmad"],"committee_members":["Davis, William A.","Besieris, Ioannis M."],"year":2003,"date_issued":"2003-10-31","date_published":"2003-10-31","updated_at":"2026-07-22T22:20:37Z","subjects":["quadrifilar helix","helical antennas","multifilar helices","NEC-4"],"languages":[],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-12112003-095406"],"render_values":[{"text":"etd-12112003-095406","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/36060","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Safaai-Jazi, Ahmad"]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Davis, William A.","Besieris, Ioannis M."]},{"key":"dc:contributor.department","label":"Department","values":["Electrical and Computer Engineering"]},{"key":"dc:creator","label":"Author","values":["Clark, Jeffrey R."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-03-14T20:49:18Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-03-14T20:49:18Z","2004-12-16"]},{"key":"dc:date.issued","label":"Date","values":["2003-10-31"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Electrical and Computer Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["quadrifilar helix","helical antennas","multifilar helices","NEC-4"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-12112003-095406"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10919/36060"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Helices are broadband antennas that provide moderate gain, largely real input impedance and circular polarization when operating in the axial mode regime. A modified form of the helix, the spherical helix, has been shown to yield similar polarization and gain characteristics over a narrow bandwidth but a much larger beamwidth. This investigation examines multifilar hemispherical helices and produces two specific designs with some desirable radiation characteristics. The side-fed quadrifilar helix and the top-fed bifilar helix are the new hemispherical designs which are studied in detail both numerically and experimentally. The Numerical Electromagnetics Code 4 is used to analyze the radiation characteristics of the proposed multifilar hemispherical helices. Directivity, E- and H-plane radiation patterns, axial ratio and input impedance of a few example designs are calculated. Measurements, taken in the anechoic chamber at the Virginia Tech antenna range, generally confirmed the simulation results. It is shown that the bifilar hemispherical helix provides a flat gain curve over the measured bandwidth (~14%) and generally elliptical polarization with near circular polarization in limited case."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:title","label":"Title","values":["Multifilar Hemispherical Helical Antennas"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Safaai-Jazi, Ahmad"],"dc:contributor.committeemember":["Davis, William A.","Besieris, Ioannis M."],"dc:contributor.department":["Electrical and Computer Engineering"],"dc:creator":["Clark, Jeffrey R."],"dc:date.accessioned":["2014-03-14T20:49:18Z"],"dc:date.available":["2014-03-14T20:49:18Z","2004-12-16"],"dc:date.issued":["2003-10-31"],"dc:description.abstract":["Helices are broadband antennas that provide moderate gain, largely real input impedance and circular polarization when operating in the axial mode regime. A modified form of the helix, the spherical helix, has been shown to yield similar polarization and gain characteristics over a narrow bandwidth but a much larger beamwidth. This investigation examines multifilar hemispherical helices and produces two specific designs with some desirable radiation characteristics. The side-fed quadrifilar helix and the top-fed bifilar helix are the new hemispherical designs which are studied in detail both numerically and experimentally. The Numerical Electromagnetics Code 4 is used to analyze the radiation characteristics of the proposed multifilar hemispherical helices. Directivity, E- and H-plane radiation patterns, axial ratio and input impedance of a few example designs are calculated. Measurements, taken in the anechoic chamber at the Virginia Tech antenna range, generally confirmed the simulation results. 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