BEGIN:VCALENDAR VERSION:2.0 PRODID:IEEE vTools.Events//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:America/New_York BEGIN:DAYLIGHT DTSTART:20250309T030000 TZOFFSETFROM:-0500 TZOFFSETTO:-0400 RRULE:FREQ=YEARLY;BYDAY=2SU;BYMONTH=3 TZNAME:EDT END:DAYLIGHT BEGIN:STANDARD DTSTART:20251102T010000 TZOFFSETFROM:-0400 TZOFFSETTO:-0500 RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=11 TZNAME:EST END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTAMP:20251008T201611Z UID:BBE525C1-3406-43E4-87DA-D02150602B4E DTSTART;TZID=America/New_York:20251007T150000 DTEND;TZID=America/New_York:20251007T163000 DESCRIPTION:The University of Michigan Radiation Lab and Trident Chapter ar e pleased to host Professor Silvio Hrabar from the University of Zagreb in Croatia. Prof. Hrabar will give a seminar\, "Application of Negative/posi tive Impedance Converters in Electrically Small Antennas" at 3:00 pm ET on Tuesday\, October 7. This talk is part of the Radlab Seminar Series.\n\nT he in-person seminar is free and open to the public and will be held in ro om GG Brown 1571 on the University of Michigan North Campus in Ann Arbor\, MI.\n\nUM Radiation Laboratory [website](https://radlab.engin.umich.edu/) \nSEM Trident Chapter (AP03/ED15/MTT17/PHO36) [website](https://r4.ieee.or g/sem/chapter-iv-trident/)\n\nSpeaker(s): Prof. Silvio Hrabar\n\nAgenda: \ nWelcome: 3:00 pm\n\nPresentation\n\nQ&A\n\nClosing\n\nApplication of Nega tive/positive Impedance Converters in Electrically Small Antennas\n\nRadla b Seminar Series\n\nDr.sc. Silvio Hrabar\n\nProfessor\nFaculty of Electric al Eng. and Comp.\, University of Zagreb\,\nUnska 3\, Zagreb\, HR-10000\,C roatia\n\nAbstract: Electrically small antennas (ESAs) are a very old but still highly challenging research topic. It is well known that classical p assive resonant matching of an ESA is inherently limited by a very narrow bandwidth due to the inevitably high Q-factor. Alternatively\, there are a ctive approaches such as non-Foster-based matching. This method uses so-ca lled Negative Impedance Converters (NICs)\, which convert ordinary reactiv e elements (capacitors and inductors) into their “negative images”: ne gative capacitors and negative inductors. The use of these negative elemen ts theoretically offers an operating bandwidth of several octaves. Unfortu nately\, this method suffers from stability problems and limited power-han dling capabilities when used in transmitting applications.\n\nIn the first part of this talk\, various approaches to overcoming stability problems i n general non-Foster-based antennas with NICs are discussed. It will be sh own that the main problem is not\, as commonly assumed\, the limitations o f the technology used (such as the occurrence of "parasitics"). Surprising ly\, the issues stem from an insufficient understanding of the physical ba ckground and the "blind" use of commercial CAD tools for stability analysi s. A simple design that leads to stable systems is explained for different types of actively matched small dipole and loop antennas. These designs u se stability-robust band-pass negative capacitors and two-transmitter non- Foster-inspired matching.\n\nThe second part addresses the concept of wide ly tunable\, perfectly matched self-oscillating and self-oscillating/ampli fying ESAs based on NICs. The basic idea is to use two identical radiators \, with one converted into its 'negative-impedance image.' Connecting a ba re radiator and its 'negative image' creates a system that supports both w idely tunable self-oscillations and non-Foster-based reflection amplificat ion.\n\nIn the third part\, it will be shown that Positive Impedance Conve rters (PICs or gyrators)\, which so far have been used very rarely in RF e ngineering\, may lead to the design of ultra-broadband directional ESAs wi th a Huygens radiation pattern.\n\nThe discussion of the above methods wil l be complemented by examples of practical experimental demonstrators oper ating in the lower RF band (< 1 GHz)\, developed at the University of Zagr eb. Finally\, some unsolved problems and related future research direction s will be highlighted.\n\nBio: Silvio Hrabar received Dipl. Ing. and M.S. degrees from University of Zagreb\, Croatia and a Ph.D degree from Brunel University of West London\, United Kingdom\, all in electrical engineering . In the past\, he was employed at various consulting\, development\, rese arch and teaching positions both in industry and academia\, in the fields of radio engineering\, microwave electronics\, antenna engineering\, elect romagnetic compatibility\, electromagnetic metrology\, computational elect romagnetics and electrostatics. Currently\, he is affiliated with Universi ty of Zagreb\, Croatia\, where he is a Professor of applied electromagneti cs. His research interest includes applied electromagnetics\, electromagne tic compatibility\, antennas\, microwave measurements and microwave engine ering. He is the author and co-author of more than 200 technical papers in journals and conferences\, many technical studies for government and indu stry\, one textbook\, and several book chapters. He also serves as a revie wer for a dozen of scientific journals in electrical engineering and appli ed physics. Professor Hrabar is a chair of Metamaterial group at Faculty o f Electrical Engineering and Computing (FER)\, University of Zagreb. In 20 12 he received ‘Award for exceptional achievements in research and innov ations’ for ‘Contribution to the understanding of basic physics of ele ctromagnetic metamaterials and development of their engineering applicatio ns’. In 2022\, 2023 and 2024\, Prof. Hrabar was ranked among the 2% most cited scientists in the world in the field of Information and communicati on technologies (Stanford University list).\n\nRoom: GGB 1571\, Bldg: GG B rown Building\, 2350 Hayward Street\, University of Michigan North Campus\ , Ann Arbor\, Michigan\, United States\, 48109 LOCATION:Room: GGB 1571\, Bldg: GG Brown Building\, 2350 Hayward Street\, U niversity of Michigan North Campus\, Ann Arbor\, Michigan\, United States\ , 48109 ORGANIZER:yms@umich.edu SEQUENCE:31 SUMMARY:Application of Negative/positive Impedance Converters in Electrical ly Small Antennas URL;VALUE=URI:https://events.vtools.ieee.org/m/505089 X-ALT-DESC:Description: <br /><p>The University of Michigan Radiation Lab a nd Trident Chapter are pleased to host Professor Silvio Hrabar from the Un iversity of Zagreb in Croatia. Prof. Hrabar will give a seminar\, &nbsp\;" <strong>Application of Negative/positive Impedance Converters in Electrica lly Small Antennas</strong>" at 3:00 pm ET on Tuesday\, October 7. This ta lk is part of the Radlab Seminar Series.</p>\n<p>The in-person seminar is free and open to the public and will be held in room GG Brown 1571 on the University of Michigan North Campus in Ann Arbor\, MI.</p>\n<p>UM Radiatio n Laboratory <a href="https://radlab.engin.umich.edu/">website</a><br>SEM Trident Chapter (AP03/ED15/MTT17/PHO36) <a href="https://r4.ieee.org/sem/c hapter-iv-trident/">website</a></p><br /><br />Agenda: <br /><p>Welcome: 3 :00 pm</p>\n<p>Presentation</p>\n<p>Q&amp\;A</p>\n<p>Closing</p>\n<p class ="MsoNormal" style="text-align: center\;" align="center"><strong><em style ="mso-bidi-font-style: normal\;"><span lang="EN-CA" style="font-size: 16.0 pt\; line-height: 115%\; color: black\; mso-themecolor: text1\; mso-ansi-l anguage: EN-CA\;">Application of Negative/positive Impedance Converters in Electrically Small Antennas</span></em></strong></p>\n<p class="MsoNormal " style="text-align: center\;" align="center"><span style="font-size: 12pt \;"><strong><em style="mso-bidi-font-style: normal\;"><span lang="EN-CA" s tyle="line-height: 115%\; color: black\;">Radlab Seminar Series</span></em ></strong></span></p>\n<table style="border-collapse: collapse\; width: 10 0%\; border-width: 1px\; border-style: none\;" border="1"><colgroup><col s tyle="width: 24.7616%\;"><col style="width: 75.2384%\;"></colgroup>\n<tbod y>\n<tr>\n<td style="text-align: left\;">\n<p style="margin: 0in\; text-al ign: left\;" align="center">&nbsp\; &nbsp\; <img src="https://events.vtool s.ieee.org/vtools_ui/media/display/8c8b5865-0803-4e60-aa28-19ed17ff95c4">< /p>\n</td>\n<td>\n<p style="margin: 0in\; text-align: left\;" align="cente r"><strong><span lang="EN-CA" style="font-size: 12.0pt\; font-family: 'Tim es New Roman'\,serif\; color: windowtext\;">Dr.sc. Silvio Hrabar</span></s trong></p>\n<p class="MsoNormal" style="margin-bottom: 0in\; text-align: l eft\;" align="center"><span style="font-size: 12.0pt\; line-height: 115%\; font-family: 'Times New Roman'\,serif\; mso-bidi-theme-font: minor-bidi\; ">Professor<br>Faculty of Electrical Eng. and Comp.\, University of Zagreb \,&nbsp\;<br>Unska 3\, Zagreb\, HR-10000\,Croatia<br><br></span></p>\n</td >\n</tr>\n</tbody>\n</table>\n<p class="MsoNormal" style="text-align: just ify\;"><strong style="mso-bidi-font-weight: normal\;"><span style="font-si ze: 12.0pt\; line-height: 115%\;">Abstract:</span></strong><span style="fo nt-size: 12.0pt\; line-height: 115%\;"> Electrically small antennas (ESAs) are a very old but still highly challenging research topic. It is well kn own that classical passive resonant matching of an ESA is inherently limit ed by a very narrow bandwidth due to the inevitably high Q-factor. Alterna tively\, there are active approaches such as non-Foster-based matching. Th is method uses so-called Negative Impedance Converters (NICs)\, which conv ert ordinary reactive elements (capacitors and inductors) into their &ldqu o\;negative images&rdquo\;: negative capacitors and negative inductors. Th e use of these negative elements theoretically offers an operating bandwid th of several octaves. Unfortunately\, this method suffers from stability problems and limited power-handling capabilities when used in transmitting applications.</span></p>\n<p class="MsoNormal" style="text-align: justify \;"><span style="font-size: 12.0pt\; line-height: 115%\;">In the first par t of this talk\, various approaches to overcoming stability problems in ge neral non-Foster-based antennas with NICs are discussed. It will be shown that the main problem is not\, as commonly assumed\, the limitations of th e technology used (such as the occurrence of "parasitics"). Surprisingly\, the issues stem from an insufficient understanding of the physical backgr ound and the "blind" use of commercial CAD tools for stability analysis. A simple design that leads to stable systems is explained for different typ es of actively matched small dipole and loop antennas. These designs use s tability-robust band-pass negative capacitors and two-transmitter non-Fost er-inspired matching.</span></p>\n<p class="MsoNormal" style="text-align: justify\;"><span style="font-size: 12.0pt\; line-height: 115%\;">The secon d part addresses the concept of widely tunable\, perfectly matched self-os cillating and self-oscillating/amplifying ESAs based on NICs. The basic id ea is to use two identical radiators\, with one converted into its 'negati ve-impedance image.' Connecting a bare radiator and its 'negative image' c reates a system that supports both widely tunable self-oscillations and no n-Foster-based reflection amplification.</span></p>\n<p class="MsoNormal" style="text-align: justify\;"><span style="font-size: 12.0pt\; line-height : 115%\;">In the third part\, it will be shown that Positive Impedance Con verters (PICs or gyrators)\, which so far have been used very rarely in RF engineering\, may lead to the design of ultra-broadband directional ESAs with a Huygens radiation pattern.</span></p>\n<p class="MsoNormal" style=" text-align: justify\;"><span style="font-size: 12.0pt\; line-height: 115%\ ;">The discussion of the above methods will be complemented by examples of practical experimental demonstrators operating in the lower RF band (&lt\ ; 1 GHz)\, developed at the University of Zagreb. Finally\, some unsolved problems and related future research directions will be highlighted.</span ></p>\n<p class="MsoNormal" style="text-align: justify\;"><strong style="m so-bidi-font-weight: normal\;"><span style="font-size: 12.0pt\; line-heigh t: 115%\;">Bio:</span></strong><span style="font-size: 12.0pt\; line-heigh t: 115%\;"> Silvio Hrabar received Dipl. Ing. and M.S. degrees from Univer sity of Zagreb\, Croatia and a Ph.D degree from Brunel University of West London\, United Kingdom\, all in electrical engineering. In the past\, he was employed at various consulting\, development\, research and teaching p ositions both in industry and academia\, in the fields of radio engineerin g\, microwave electronics\, antenna engineering\, electromagnetic compatib ility\, electromagnetic metrology\, computational electromagnetics and ele ctrostatics. Currently\, he is affiliated with University of Zagreb\, Croa tia\, where he is a Professor of applied electromagnetics. His research in terest includes applied electromagnetics\, electromagnetic compatibility\, antennas\, microwave measurements and microwave engineering. He is the au thor and co-author of more than 200 technical papers in journals and confe rences\, many technical studies for government and industry\, one textbook \, and several book chapters. He also serves as a reviewer for a dozen of scientific journals in electrical engineering and applied physics. Profess or Hrabar is a chair of Metamaterial group at Faculty of Electrical Engine ering and Computing (FER)\, University of Zagreb. In 2012 he received &lsq uo\;Award for exceptional achievements in research and innovations&rsquo\; for &lsquo\;Contribution to the understanding of basic physics of electro magnetic metamaterials and development of their engineering applications&r squo\;. In 2022\, 2023 and 2024\, Prof. Hrabar was ranked among the 2% mos t cited scientists in the world in the field of Information and communicat ion technologies (Stanford University list).</span></p> END:VEVENT END:VCALENDAR