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

The paper studies the properties of the far field of a primary-fed parabolic reflector fed by a four-port L-band Eleven antenna. The sum beam as well as difference beams in two orthogonal planes after the reflector, which are necessary for the mono-pulse tracking, have been numerically evaluated. In addition, the relationship between the spacing between two parallel folded dipoles and the matching as well as radiation properties has been investigated.

http://www.wseas.us/e-library/conferences/2008/norway/electroscience/11-electroscience.pdf

Study on a parabolic reflector fed by L-band multi-port eleven antenna

A longitudinally corrugated circular waveguide with dielectric-filled grooves of alternating depths is considered. The dispersion equation for determining the waveguide eigenmode parameters is derived for the small corrugation period. The waveguide is shown to support two quasi-transversal electromagnetic (TEM) modes, associated with each of the two frequencies at which the TEM condition is realised. Some features of these quasi-TEM modes are revealed. The potential performance of a dual-band conical horn is presented, and some future studies are discussed here.

Modal solutions in dual-depth longitudinally corrugated hard waveguide

Two wideband vertical transitions from inverted microstrip gap waveguide to rectangular waveguide (WR-15) for 60 GHz antenna array applications are proposed. These transitions are aimed to interconnect the WR-15 with the gap waveguide feed-network employed to provide feeding to the radiating elements of slot/horn antenna arrays. The wideband field transformation is achieved without the need of adding a quarter-wavelength cavity backshort on a metal block placed over the transition. First, we replace this backshort by creating a cavity in the radiating layer when this is made in Substrate Integrated Waveguide (SIW) technology, and thereafter we use an air-filled pin cavity in the radiating layer. The simulated Sparameters show that the presented transitions cover the unlicensed 60 GHz band (57–64 GHz) with good margins.

https://publications.lib.chalmers.se/records/fulltext/227745/local_227745.pdf

Design of millimeter-wave wideband gap waveguide transitions considering integration into the antenna system

The paper studies the over-the-air (OTA) performance of a mobile terminal. A practical two-port mobile terminal model on the left side and the right side of the head for both standard cheek position and standard tilt position is used to study the diversity gains. The diversity gain has been determined by measurements in a reverberation chamber as well as by simulations using the far field patterns from CST Microwave Studio, and then exposing these patterns to rich isotropic multipath (RIMP) environment in a ray-based simulation tool.

https://publications.lib.chalmers.se/records/fulltext/186977/local_186977.pdf

Diversity gains of multiport mobile terminals in multipath for talk positions on both sides of the head

The paper describes a method to phase-steer a linear array antenna to a discrete number of directions by rearranging the sequence of phase cables that are connected to each array element. The phase cables must be precut to specific lengths which are evaluated. The idea is applied to the EISCAT parabolic cylinder antenna in Tromso Norway.

Per-Simon Kildal

Papers

Study on a parabolic reflector fed by L-band multi-port eleven antenna

Modal solutions in dual-depth longitudinally corrugated hard waveguide

Design of millimeter-wave wideband gap waveguide transitions considering integration into the antenna system

Diversity gains of multiport mobile terminals in multipath for talk positions on both sides of the head

Discrete phase-steering by permuting precut phase cables