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 first-order correction to the physical optics (PO) solution for the axial radiation field from parabolic reflector antennas is found. The correction is of order k^{-1} and is in quadrature with the PO solution. By means of the correction term the accuracy of the PO surface integral is round to be better than 0.22(\lambda/D)^{2} dB on axis, where D is the diameter of the reflector. Thus, the PO solution for the directivity is extremely accurate for commun reflector sizes of several wavelengths \lambda .

On the accuracy of physical optics

The self-grounded antenna is a new type of compact ultra-wideband antennas with simple geometries. One of the characteristics of this type antenna is its high flexibility: the configuration of the antenna can be arranged in many different ways for different applications. In this paper, we overview the typical arrangements of the self-grounded antennas, and their performance for different applications.

/pdf/arrangements-and-applications-of-self-grounded-antennas-4f43u76kru.pdf

Arrangements and applications of self-grounded antennas

The dyadic reflection coefficient of a planar surface consisting of parallel PEC and PMC strips is derived and used to study radiation patterns of dipoles located over the surface. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 583–587 2006; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.21414

Dyadic GO reflection coefficient for PEC/PMC strip surface and application to the planar case for dipole radiation

In this paper, we present characterizations of multi-antenna systems in two opposite edge environments, i.e., rich isotropic multipath (RIMP) and random line-of-sight (LOS) environments. We use the detection probability of the single or multiple bit streams (for diversity and multiplexing cases, respectively) over an ensemble of users as the characterizing quantity. The relationship between the detection probability and the throughput in RIMP is given. An wideband compact multi-port antenna is used as an example to show characterizations in both RIMP and random-LOS environment.

https://www.ursi.org/Proceedings/ProcGA14/papers/ursi_paper2397.pdf

Characterization of multi-antenna systems in RIMP and random-LOS environments using probability of detection of different bit streams

http://ieeexplore.ieee.org/iel6/8256/25862/01149154.pdf

Per-Simon Kildal

Papers

On the accuracy of physical optics

Arrangements and applications of self-grounded antennas

Dyadic GO reflection coefficient for PEC/PMC strip surface and application to the planar case for dipole radiation

Characterization of multi-antenna systems in RIMP and random-LOS environments using probability of detection of different bit streams

Directivity-optimization of a small resonant reflector antenna