A new type of metallic electromagnetic structure has been developed that is characterized by having high surface impedance. Although it is made of continuous metal, and conducts dc currents, it does not conduct ac currents within a forbidden frequency band. Unlike normal conductors, this new surface does not support propagating surface waves, and its image currents are not phase reversed. The geometry is analogous to a corrugated metal surface in which the corrugations have been folded up into lumped-circuit elements, and distributed in a two-dimensional lattice. The surface can be described using solid-state band theory concepts, even though the periodicity is much less than the free-space wavelength. This unique material is applicable to a variety of electromagnetic problems, including new kinds of low-profile antennas.

/pdf/high-impedance-electromagnetic-surfaces-with-a-forbidden-3vtu72a5an.pdf

High-impedance electromagnetic surfaces with a forbidden frequency band

Herschel was launched on 14 May 2009, and is now an operational ESA space observatory o ering unprecedented observational capabilities in the far-infrared and submillimetre spectral range 55 671 m. Herschel carries a 3.5 metre diameter passively cooled Cassegrain telescope, which is the largest of its kind and utilises a novel silicon carbide technology. The science payload comprises three instruments: two direct detection cameras/medium resolution spectrometers, PACS and SPIRE, and a very high-resolution heterodyne spectrometer, HIFI, whose focal plane units are housed inside a superfluid helium cryostat. Herschel is an observatory facility operated in partnership among ESA, the instrument consortia, and NASA. The mission lifetime is determined by the cryostat hold time. Nominally approximately 20,000 hours will be available for astronomy, 32% is guaranteed time and the remainder is open to the worldwide general astronomical community through a standard competitive proposal procedure.

/pdf/herschel-space-observatory-an-esa-facility-for-far-infrared-3pdcouv7zo.pdf

Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy

The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Transformation optics describes the capability to design the path of light waves almost at will through the use of metamaterials that control effective materials properties on a subwavelength scale. In this review, the physics and applications of transformation optics are discussed.

Transformation optics and metamaterials

Science and technologies based on terahertz frequency electromagnetic radiation (100 GHz–30 THz) have developed rapidly over the last 30 years. For most of the 20th Century, terahertz radiation, then referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to 'real world' applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2017, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 18 sections that cover most of the key areas of THz science and technology. We hope that The 2017 Roadmap on THz science and technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies.

https://iopscience.iop.org/article/10.1088/1361-6463/50/4/043001/pdf

The 2017 terahertz science and technology roadmap

Diffraction efficiencies of reflector antennas

In this paper a double layer cavity backed slot array antenna at K band is presented. The slot antenna is built using ridge gap waveguide feed network and gap waveguide cavity layer. These antenna blocks are manufactured without the requirements of electrical contact between the metal plates The corporate-feed network is realized by a texture of pins and a guiding ridge in the bottom plate. The 4×4 slot array antenna has been fabricated and measured. The measured reflection coefficient remains below −11dB with reasonably good radiation patterns over the band of interest from 18.2 GHz to 21.2 GHz.

/pdf/design-of-a-double-layer-cavity-backed-slot-array-antenna-in-39szy99aoj.pdf

Design of a double layer cavity backed slot array antenna in gap waveguide technology

The Eleven feed, featured as a low-profile, logarithmic-periodic and ultra wideband antenna, has during the past few years been developed at Chalmers [1]-[5]. It is referred to as the Eleven feed because its basic geometry is two parallel folded dipoles half-wavelength apart, and it can be used over more than a decade bandwidth with 11dBi directivity by extending the basic configuration logarithmically. The Eleven feed can be used in both linear and dual polarizations, and its phase centre changes so little with frequency that the corresponding phase efficiency is better than -0.1dB at all frequencies. The 10dB semi-beam width is 50-60 degrees over the entire frequency band, and a reflector aperture efficiency of 66% or better can be achieved when the subtended angle towards the reflector is about 53 degrees. Therefore, it is suitable as feed for reflector antennas, in particular when they are primary-fed. The Eleven feed was developed on projects for California Institute of Technology (Caltech) as a feed for the reflectors of the US SKA proposal (Square Kilometer Array) [2].

http://publications.lib.chalmers.se/records/fulltext/local_44932.pdf

The Eleven antenna feed for monopulse tracking and combining L-, C-, X- and Ku- satellite bands

/pdf/cryogenic-integration-of-2-14-ghz-eleven-feed-in-wideband-1bxpzyotgp.pdf

Cryogenic integration of 2-14 GHz Eleven Feed in wideband receiver for VLBI 2010

A passive power splitter and combiner has been designed in-between two metallic ground plates using gap waveguide technology. The measured insertion loss is smaller than 2.3 dB and the return loss is larger than 10 dB over the entire W-band (75–110 GHz). The design procedure has been detailed and the simulated and measured results for the proposed structure are shown. The designed structure can be used as a passive power splitter or combiner, as a grid amplifier in a back-to-back RF chain, or as a quasi-optical beamforming component in beam steering antenna arrays.

/pdf/w-band-spatial-power-combiner-and-splitter-in-gap-waveguide-22snhki2f8.pdf

Per-Simon Kildal

Papers

Diffraction efficiencies of reflector antennas

Design of a double layer cavity backed slot array antenna in gap waveguide technology

The Eleven antenna feed for monopulse tracking and combining L-, C-, X- and Ku- satellite bands

Cryogenic integration of 2-14 GHz Eleven Feed in wideband receiver for VLBI 2010

W-band spatial power combiner and splitter in gap waveguide technology