{"647251":{"#nid":"647251","#data":{"type":"event","title":"Ph.D. Proposal Oral Exam - Edward Slevin","body":[{"value":"\u003Cp\u003E\u003Cstrong\u003ETitle:\u0026nbsp; \u003C\/strong\u003E\u003Cem\u003EBroadband Non-Resonant Electrically-Small VLF\/LF Transmitter Realized by Rapidly Time-Varying Antenna Properties\u003C\/em\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cstrong\u003ECommittee:\u0026nbsp; \u003C\/strong\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003EDr. Cohen, Advisor\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003EDr. Peterson, Chair\u003C\/p\u003E\r\n\r\n\u003Cp\u003EDr. Saeedifard\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cstrong\u003EAbstract: \u003C\/strong\u003EThe objective of the proposed research is to numerically and experimentally validate the operation of a novel time-domain matching scheme for electrically-small antennas (ESAs) in the Very Low Frequency (VLF, 3-30 kHz) and Low Frequency (LF, 30-300 kHz) bands. VLF\/LF signals have exceptionally long wavelengths, which make them well-suited to critical applications such as underwater communication, but also difficult to generate from an ESA. Conventional solutions utilize a resonant matching network to enhance ESA efficiency, but at the cost of a narrow bandwidth. Any linear time-invariant antenna is in fact fundamentally constrained by the Chu-Harrington limit, which places an upper bound on operational bandwidth. Several antenna solutions have managed to perform beyond the Chu limit by operating in a time-varying manner, but all such approaches have relied upon resonance and are thus still band-limited. Here, a new time-varying antenna is proposed in which impedance matching is performed in the time-domain.\u0026nbsp;\u0026nbsp;By breaking up a VLF\/LF signal into narrow pulses, any reflected current can be prevented from returning to the antenna feed by rapidly varying the antenna\u0026rsquo;s conductivity over time. In doing so, the antenna becomes non-reciprocal and impedance matched to its source, but without any restriction on bandwidth since the matching occurs in the time-domain. Preliminary simulations and experiments confirm the ability to suppress reflections in this manner and suggest an improvement in radiated power. However, further modeling must be done to examine the far-field behavior of the antenna and quantify its performance. Moreover, wireless transmission measurements must be taken to prove that the antenna generates fields resembling that of an infinitesimal electric monopole.\u0026nbsp;\u003C\/p\u003E\r\n","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":"","field_summary_sentence":[{"value":"Broadband Non-Resonant Electrically-Small VLF\/LF Transmitter Realized by Rapidly Time-Varying Antenna Properties"}],"uid":"28475","created_gmt":"2021-05-07 11:54:46","changed_gmt":"2021-05-07 11:54:46","author":"Daniela Staiculescu","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2021-05-19T12:00:00-04:00","event_time_end":"2021-05-19T14:00:00-04:00","event_time_end_last":"2021-05-19T14:00:00-04:00","gmt_time_start":"2021-05-19 16:00:00","gmt_time_end":"2021-05-19 18:00:00","gmt_time_end_last":"2021-05-19 18:00:00","rrule":null,"timezone":"America\/New_York"},"extras":[],"groups":[{"id":"434371","name":"ECE Ph.D. Proposal Oral Exams"}],"categories":[],"keywords":[{"id":"102851","name":"Phd proposal"},{"id":"1808","name":"graduate students"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78771","name":"Public"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}