BEGIN:VCALENDAR VERSION:2.0 PRODID:IEEE vTools.Events//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:Asia/Kolkata BEGIN:STANDARD DTSTART:19451014T230000 TZOFFSETFROM:+0630 TZOFFSETTO:+0530 TZNAME:IST END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTAMP:20260322T092443Z UID:7A724C24-B3DE-4A99-8D82-F4A40FCBCD23 DTSTART;TZID=Asia/Kolkata:20260317T200000 DTEND;TZID=Asia/Kolkata:20260317T210000 DESCRIPTION:Abstract of the Talk:\n\nHighly directive antenna systems are b eing sought to address the perceived needs of FutureG wireless systems and their applications. Practical alternatives to complex\, power-hungry phas ed arrays are truly desired. A potential approach is to develop and employ compact superdirective systems. An endfire-radiating system is commonly s aid to be superdirective if its maximum directivity Dmax surpasses the Har rington normal directivity bound: DHarrington = (ka)2 + 2 ka\, where ka is the system’s overall electrical size. A broadside-radiating system is t ermed superdirective if its Dmax > 4p A / l2\, where A is its (aperture) a rea orthogonal to the broadside direction and it is uniformly excited with a signal having the wavelength l.\n\nThe concept of “needle” radiatio n and the accompanying abstraction of superdirectivity was introduced by O seen in the physics community over 100 years ago. Numerous applied electro magnetics (EM) papers then followed over the last half of the last century that discussed the interesting attributes of unlimited directivity\, i.e. \, superdirectivity\, from arbitrarily small source regions and arrays. Ne vertheless\, the consensus in the EM community generally has been that sup erdirective systems are impractical for wide variety of reasons. However\, a turning point in superdirectivity history occurred early this century w ith the successful demonstrations of electrically small\, superdirective t wo-element endfire arrays of electric elements. Several superdirective mul ti-element endfire arrays of either electric or magnetic dipole elements h ave been demonstrated over the last decade.\n\nThose original theoretical notions of superdirectivity have been confirmed recently with explicit sol utions of Maxwell’s equations based upon vector spherical wave expansion analyses. These solutions and the physics they have revealed will be disc ussed along with their implications for the engineering of practical super directive systems. A multipole engineering paradigm has evolved that equip s us with several practical approaches to realizing both superdirective br oadside-radiating and endfire-radiating systems. They include unidirection al mixed-multipole antennas (MMAs) based on combinations of electric and m agnetic near-field resonant parasitic (NFRP) elements that radiate multipo le fields when they are excited by simple driven dipoles. Another strategy is to employ Huygens dipole antennas in a sector of a uniform circular ar ray that are excited with custom-designed amplitudes to radiate mixtures o f azimuthal eigenmodes. Yet another technique is to employ an MMA to excit e both the electric and magnetic multipoles of a multilayered spherical di electric lens that combine into unidirectional superdirective fields.\n\nT he historical aspects of superdirective systems from the 20th century and the electromagnetics – both physics and engineering features – of the 21st century’s innovative realizations of practical superdirective syste ms will be reviewed. They encourage further superdirective research activi ties since they demonstrate that practical superdirective radiating system s are\, in fact\, achievable.\n\nSpeaker(s): Prof. Richard W. Ziolkowski\, \n\nVirtual: https://events.vtools.ieee.org/m/546518 LOCATION:Virtual: https://events.vtools.ieee.org/m/546518 ORGANIZER:IEEE.apmtts.sbciitkgp@gmail.com SEQUENCE:30 SUMMARY:Practical Superdirectivity—Back to the Future URL;VALUE=URI:https://events.vtools.ieee.org/m/546518 X-ALT-DESC:Description: <br /><div style="text-align: justify\;"><span styl e="color: #000000\; font-family: arial\, sans-serif\;"><strong>Abstract of the Talk:</strong></span></div>\n<div style="text-align: justify\;"><span style="color: #000000\; font-family: arial\, sans-serif\;"><strong>&nbsp\ ;</strong></span></div>\n<div>\n<div>\n<div dir="auto">\n<p class="MsoNorm al" style="text-align: justify\;"><span style="font-family: arial\, sans-s erif\;"><span lang="EN-US">Highly directive antenna systems are being soug ht to address the perceived needs of FutureG wireless systems and their ap plications. Practical alternatives to complex\, power-hungry phased arrays are truly desired. A potential approach is to develop and employ compact superdirective systems. An&nbsp\;<em>endfire-radiating system</em>&nbsp\;i s commonly said to be superdirective if its maximum directivity&nbsp\;<em> D</em><sub>max</sub>&nbsp\;surpasses the Harrington normal directivity bou nd:&nbsp\;<em>D</em><sub>Harrington&nbsp\;</sub>= (<em>ka</em>)<sup>2</sup >&nbsp\;+ 2&nbsp\;<em>ka</em>\, where&nbsp\;<em>ka</em>&nbsp\;is the syste m&rsquo\;s overall electrical size. A&nbsp\;<em>broadside-radiating system </em>&nbsp\;is termed superdirective if its&nbsp\;<em>D</em><sub>max</sub> &nbsp\;&gt\; 4</span><span lang="EN-US">p</span><span lang="EN-US">&nbsp\; <em>A</em>&nbsp\;/&nbsp\;</span><span lang="EN-US">l</span><sup><span lang ="EN-US">2</span></sup><span lang="EN-US">\, where&nbsp\;<em>A</em>&nbsp\; is its (aperture) area orthogonal to the broadside direction and it is uni formly excited with a signal having the wavelength&nbsp\;</span><span lang ="EN-US">l</span><span lang="EN-US">.</span></span></p>\n<p class="MsoNorm al" style="text-align: justify\;"><span lang="EN-US"><span style="font-fam ily: arial\, sans-serif\;">&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\; The concept of &ldquo\;needle&rdquo\; radiation and the accompanying abstraction of s uperdirectivity was introduced by Oseen in the physics community over 100 years ago. Numerous applied electromagnetics (EM) papers then followed ove r the last half of the last century that discussed the interesting attribu tes of unlimited directivity\, i.e.\, superdirectivity\, from arbitrarily small source regions and arrays. Nevertheless\, the consensus in the EM co mmunity generally has been that superdirective systems are impractical for wide variety of reasons. However\, a turning point in superdirectivity hi story occurred early this century with the successful demonstrations of el ectrically small\, superdirective two-element endfire arrays of electric e lements. Several superdirective multi-element endfire arrays of either ele ctric or magnetic dipole elements have been demonstrated over the last dec ade.</span></span></p>\n<p class="MsoNormal" style="text-align: justify\;" ><span lang="EN-US"><span style="font-family: arial\, sans-serif\;">&nbsp\ ;&nbsp\;&nbsp\;&nbsp\;&nbsp\; Those original theoretical notions of superd irectivity have been confirmed recently with explicit solutions of Maxwell &rsquo\;s equations based upon vector spherical wave expansion analyses. T hese solutions and the physics they have revealed will be discussed along with their implications for the engineering of practical superdirective sy stems. A&nbsp\;<em>multipole engineering</em>&nbsp\;paradigm has evolved t hat equips us with several practical approaches to realizing both superdir ective broadside-radiating and endfire-radiating systems. They include uni directional mixed-multipole antennas (MMAs) based on combinations of elect ric and magnetic near-field resonant parasitic (NFRP) elements that radiat e multipole fields when they are excited by simple driven dipoles. Another strategy is to employ Huygens dipole antennas in a sector of a uniform ci rcular array that are excited with custom-designed amplitudes to radiate m ixtures of azimuthal eigenmodes. Yet another technique is to employ an MMA to excite both the electric and magnetic multipoles of a multilayered sph erical dielectric lens that combine into unidirectional superdirective fie lds.</span></span></p>\n<p class="MsoNormal" style="text-align: justify\;" ><span lang="EN-US"><span style="font-family: arial\, sans-serif\;">&nbsp\ ;&nbsp\;&nbsp\;&nbsp\;&nbsp\; The historical aspects of superdirective sys tems from the 20<sup>th</sup>&nbsp\;century and the electromagnetics &ndas h\; both physics and engineering features &ndash\; of the 21<sup>st</sup>& nbsp\;century&rsquo\;s innovative realizations of practical superdirective systems will be reviewed. They encourage further superdirective research activities since they demonstrate that practical superdirective radiating systems are\, in fact\, achievable.</span></span></p>\n</div>\n</div>\n</d iv> END:VEVENT END:VCALENDAR