BEGIN:VCALENDAR VERSION:2.0 PRODID:IEEE vTools.Events//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:America/Montreal BEGIN:DAYLIGHT DTSTART:20210314T030000 TZOFFSETFROM:-0500 TZOFFSETTO:-0400 RRULE:FREQ=YEARLY;BYDAY=2SU;BYMONTH=3 TZNAME:EDT END:DAYLIGHT BEGIN:STANDARD DTSTART:20201101T010000 TZOFFSETFROM:-0400 TZOFFSETTO:-0500 RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=11 TZNAME:EST END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTAMP:20201109T171755Z UID:BFC68EB7-6741-4758-978D-E664268DF643 DTSTART;TZID=America/Montreal:20201109T100000 DTEND;TZID=America/Montreal:20201109T110000 DESCRIPTION:Lens antennas are commonly englobed in a more general type of a ntennas\, named aperture antennas. As their name indicates\, they make use of a lens to modify the field distribution at the aperture of the antenna \, which is typically fed by a single source. The lens is employed to tran sform the waves arriving from the source into a desired radiation pattern. Commonly\, the desired radiation pattern is a directive beam in a given d irection. However\, similar to arrays\, reflectors or leaky wave antennas\ , the goal changes depending on the application. For example\, other desir ed features may be to produce multiple beams\, or a broad beam-width.\nLen ses were more commonly employed in optical applications. For this reason\, most of the nomenclature comes from optics\, and they are evaluated with rays theory. In this sense\, the performance of the lens is conventionally described in terms of aberrations. An aberration is a failure of the rays to converge at the desired focus. This failure must be due to a defect or an improper design. Aberrations are classified as chromatic or monochroma tic\, depending on whether or not they have a frequency dependence. There are five monochromatic aberrations: spherical aberration\, coma\, astigmat ism\, Petzval field curvature\, and distortion. However\, this is not a co mmon nomenclature for antenna designers in the radio-frequency and microwa ve regimes. In these regimes\, the rays are substituted by electromagnetic fields\, and the designers evaluate their antennas in terms of directivit y\, gain\, efficiency\, side lobe levels\, cross polarization levels\, etc . Therefore\, there is a communication gap between both communities: optic s and microwaves. In the THz regime\, which is in between these two commun ities\, researchers must understand both nomenclatures\nIn this talk\, I w ill explain the operation of lens antennas\, their potential\, and two inn ovative techniques that have become very important in recent years. The fi rst technique is transformation optics\, which can be employed to produce three-dimensional directive lenses. The second one is metasurfaces\, which can be used to produce low-cost and planar two-dimensional lenses. In the case of metasurfaces\, fully metallic solutions are possible\, which is a clear advantage in terms of losses. However\, with the available technolo gy\, metasurfaces are only able to scan in one single plane. Finally\, we introduce the concept of higher symmetries\, that can be employed to enhan ce the bandwidth of conventional metasurfaces\, or to increase their equiv alent refractive indexes.\n\nSpeaker(s): Oscar Quevedo-Teruel\, \n\nVirtua l: https://events.vtools.ieee.org/m/247088 LOCATION:Virtual: https://events.vtools.ieee.org/m/247088 ORGANIZER:robert.paknys@concordia.ca SEQUENCE:4 SUMMARY:Lens Antennas: Fundamentals and Present Applications URL;VALUE=URI:https://events.vtools.ieee.org/m/247088 X-ALT-DESC:Description: <br /><p>Lens antennas are commonly englobed in a m ore general type of antennas\, named aperture antennas. As their name indi cates\, they make use of a lens to modify the field distribution at the ap erture of the antenna\, which is typically fed by a single source. The len s is employed to transform the waves arriving from the source into a desir ed radiation pattern. Commonly\, the desired radiation pattern is a direct ive beam in a given direction. However\, similar to arrays\, reflectors or leaky wave antennas\, the goal changes depending on the application. For example\, other desired features may be to produce multiple beams\, or a b road beam-width.<br /> Lenses were more commonly employed in optical appli cations. For this reason\, most of the nomenclature comes from optics\, an d they are evaluated with rays theory. In this sense\, the performance of the lens is conventionally described in terms of aberrations. An aberratio n is a failure of the rays to converge at the desired focus. This failure must be due to a defect or an improper design. Aberrations are classified as chromatic or monochromatic\, depending on whether or not they have a fr equency dependence. There are five monochromatic aberrations: spherical ab erration\, coma\, astigmatism\, Petzval field curvature\, and distortion. However\, this is not a common nomenclature for antenna designers in the r adio-frequency and microwave regimes. In these regimes\, the rays are subs tituted by electromagnetic fields\, and the designers evaluate their anten nas in terms of directivity\, gain\, efficiency\, side lobe levels\, cross polarization levels\, etc. Therefore\, there is a communication gap betwe en both communities: optics and microwaves. In the THz regime\, which is i n between these two communities\, researchers must understand both nomencl atures<br /> In this talk\, I will explain the operation of lens antennas\ , their potential\, and two innovative techniques that have become very im portant in recent years. The first technique is transformation optics\, wh ich can be employed to produce three-dimensional directive lenses. The sec ond one is metasurfaces\, which can be used to produce low-cost and planar two-dimensional lenses. In the case of metasurfaces\, fully metallic solu tions are possible\, which is a clear advantage in terms of losses. Howeve r\, with the available technology\, metasurfaces are only able to scan in one single plane. Finally\, we introduce the concept of higher symmetries\ , that can be employed to enhance the bandwidth of conventional metasurfac es\, or to increase their equivalent refractive indexes.</p>\n<p>&nbsp\;</ p> END:VEVENT END:VCALENDAR