{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/101641"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/101641","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Switched aperture surface current measurements","abstract":"The measurement of induced surface currents on antennas, scatterers, and other structures is important for a variety of reasons, including in-situ measurements and validation of simulated results. Techniques for measuring the complete vector nature of surface currents (magnitude, direction, and phase) have relied on probes that perturb the spatial structure of the field. Provided this perturbation is sufficiently small and/or well-characterized, reasonably accurate results may be obtained. In other words, these methods assume that the perturbed fields are sufficiently similar to the unperturbed fields that measurements of the former may be substituted for values of the latter. In this work, a general theory referred to as a switched aperture surface current measurement is developed that directly obtains unperturbed electric surface current measurements, provided certain conditions on the measurement apparatus are met. The most stringent of these are the requirement for a backplane region, fully isolated from the measurement environment, and the requirement that the environment and sources generating the currents do not change significantly when a measurement aperture is switched between open and shorted states. Provided these conditions are met, the theory removes the conventional measurement probe trade-off between measurement accuracy and probe size, since probe size is conventionally proportional to signal-to-noise ratio and inversely proportional to field disturbance and hence accuracy. This theory should thus allow for the creation of highly accurate surface current measurement apparatuses in special cases. The relevant background and supporting theory are developed here for the switched aperture measurement technique, followed by the development and analysis of two calibration theories necessary to utilize the technique in practice. An in-depth study of a simulated, example measurement apparatus is conducted, which is used to draw a number of conclusions and to propose future work.","abstract_html":"The measurement of induced surface currents on antennas, scatterers, and other structures is important for a variety of reasons, including in-situ measurements and validation of simulated results. Techniques for measuring the complete vector nature of surface currents (magnitude, direction, and phase) have relied on probes that perturb the spatial structure of the field. Provided this perturbation is sufficiently small and/or well-characterized, reasonably accurate results may be obtained. In other words, these methods assume that the perturbed fields are sufficiently similar to the unperturbed fields that measurements of the former may be substituted for values of the latter. In this work, a general theory referred to as a switched aperture surface current measurement is developed that directly obtains unperturbed electric surface current measurements, provided certain conditions on the measurement apparatus are met. The most stringent of these are the requirement for a backplane region, fully isolated from the measurement environment, and the requirement that the environment and sources generating the currents do not change significantly when a measurement aperture is switched between open and shorted states. Provided these conditions are met, the theory removes the conventional measurement probe trade-off between measurement accuracy and probe size, since probe size is conventionally proportional to signal-to-noise ratio and inversely proportional to field disturbance and hence accuracy. This theory should thus allow for the creation of highly accurate surface current measurement apparatuses in special cases. The relevant background and supporting theory are developed here for the switched aperture measurement technique, followed by the development and analysis of two calibration theories necessary to utilize the technique in practice. An in-depth study of a simulated, example measurement apparatus is conducted, which is used to draw a number of conclusions and to propose future work.","abstract_has_math":false,"creators":["Gibbons, Brian B."],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Electrical & Computer Engr","degree_department":null,"school":null,"contributors":["Bernhard, Jennifer","Franke, Steven","Schutt-Ainé, José","Bahl, Gaurav"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018-09-27T16:28:01Z","date_published":"2018-09-27T16:28:01Z","updated_at":"2026-07-22T22:24:40Z","subjects":["surface current measurement","surface current probe","magnetic field probe","switched aperture measurement","aperture coupling","slot coupling","metrology","surface currents","RF currents","microwave currents","antenna currents"],"languages":["en"],"rights":["Copyright 2018 Brian B. Gibbons"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/101641","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Bernhard, Jennifer","Franke, Steven","Schutt-Ainé, José","Bahl, Gaurav"]},{"key":"dc:creator","label":"Author","values":["Gibbons, Brian B."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2018-09-27T16:28:01Z","2020-09-28T09:15:07Z","2018-05-17","2018-08"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Electrical & Computer Engr"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["surface current measurement","surface current probe","magnetic field probe","switched aperture measurement","aperture coupling","slot coupling","metrology","surface currents","RF currents","microwave currents","antenna currents"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2018 Brian B. 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In this work, a general theory referred to as a switched aperture surface current measurement is developed that directly obtains unperturbed electric surface current measurements, provided certain conditions on the measurement apparatus are met. The most stringent of these are the requirement for a backplane region, fully isolated from the measurement environment, and the requirement that the environment and sources generating the currents do not change significantly when a measurement aperture is switched between open and shorted states. Provided these conditions are met, the theory removes the conventional measurement probe trade-off between measurement accuracy and probe size, since probe size is conventionally proportional to signal-to-noise ratio and inversely proportional to field disturbance and hence accuracy. This theory should thus allow for the creation of highly accurate surface current measurement apparatuses in special cases. The relevant background and supporting theory are developed here for the switched aperture measurement technique, followed by the development and analysis of two calibration theories necessary to utilize the technique in practice. An in-depth study of a simulated, example measurement apparatus is conducted, which is used to draw a number of conclusions and to propose future work.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2020-08-01","The student, Brian Gibbons, accepted the attached license on 2018-05-16 at 16:22.","The student, Brian Gibbons, submitted this Dissertation for approval on 2018-05-16 at 16:33.","This Dissertation was approved for publication on 2018-05-17 at 13:00.","DSpace SAF Submission Ingestion Package generated from Vireo submission #12577 on 2018-09-27 at 11:15:43","Made available in DSpace on 2018-09-27T16:28:01Z (GMT). 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Techniques for measuring the complete vector nature of surface currents (magnitude, direction, and phase) have relied on probes that perturb the spatial structure of the field. Provided this perturbation is sufficiently small and/or well-characterized, reasonably accurate results may be obtained. In other words, these methods assume that the perturbed fields are sufficiently similar to the unperturbed fields that measurements of the former may be substituted for values of the latter. In this work, a general theory referred to as a switched aperture surface current measurement is developed that directly obtains unperturbed electric surface current measurements, provided certain conditions on the measurement apparatus are met. The most stringent of these are the requirement for a backplane region, fully isolated from the measurement environment, and the requirement that the environment and sources generating the currents do not change significantly when a measurement aperture is switched between open and shorted states. Provided these conditions are met, the theory removes the conventional measurement probe trade-off between measurement accuracy and probe size, since probe size is conventionally proportional to signal-to-noise ratio and inversely proportional to field disturbance and hence accuracy. This theory should thus allow for the creation of highly accurate surface current measurement apparatuses in special cases. The relevant background and supporting theory are developed here for the switched aperture measurement technique, followed by the development and analysis of two calibration theories necessary to utilize the technique in practice. An in-depth study of a simulated, example measurement apparatus is conducted, which is used to draw a number of conclusions and to propose future work.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2020-08-01","The student, Brian Gibbons, accepted the attached license on 2018-05-16 at 16:22.","The student, Brian Gibbons, submitted this Dissertation for approval on 2018-05-16 at 16:33.","This Dissertation was approved for publication on 2018-05-17 at 13:00.","DSpace SAF Submission Ingestion Package generated from Vireo submission #12577 on 2018-09-27 at 11:15:43","Made available in DSpace on 2018-09-27T16:28:01Z (GMT). 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