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

Gap waveguide technology represents an interesting alternative as low-loss, cost-effective and high-performance transmission line and package of microwave and millimeter-wave systems. A Ka-band coupled-resonator filter for a radio link diplexer, which requires high selectivity to isolate transmit and receiving channels, is proposed and realized using gap waveguide technology. The band-pass filter, which has a central frequency of 37.37 GHz and a pass bandwidth of 560 MHz, is fabricated between two metal parallel plates leaving an air gap between them. Measurements show a minimum in-band insertion loss of 1 dB and agree quite well with simulations.

https://publications.lib.chalmers.se/records/fulltext/166921/local_166921.pdf

Ka-band gap waveguide coupled-resonator filter for radio link diplexers

“Impressive Success” is, of course, not our words, but we take them to our hearts and want to share them with the readers of the Antennas and Propagation Magazine. And, yes, we were also satisfied with the arrangements of EuCAP 2013. The SCC venue (Swedish Exhibition & Congress Center) was very modern and practical; the collaboration with EurAAP as well as the professional conference organizers was to the satisfaction of all of us. Most important is all the positive feedback we have received from the attendees, who “even” were satisfied with the food provided by the venue restaurant, which was of high quality (the “even” refers to the fact that food is not what Sweden is most world-famous for). According to the EurAAP Chair: “EuCAP is after the Gothenburg edition, a top quality and worldwide appreciated conference.”

EuCAP 2013 in Gothenburg, Sweden: “An Impressive Success” [EurAAP Corner]

Recently the so-called DB boundary conditions were introduced that exhibit characteristics similar to that of an isotropic soft surface, except for an anomaly at normal incidence. This anomaly has also been amended, and the amended DB boundary condition has been shown to represent reflection from an EBG surface within the bandgap. The present paper summarizes the calculated characteristics of a practical planar EBG surface when modelled both with CST and the homogenous PMC-amended DB boundary condition. The paper also shows that the surface of an anistrotropic material with zero eps_z and mu_z will behave similar to the original DB boundary condition, and this is used to understand the anomaly for normal incidence by studying the case of eps_z and mu_z approaching zero.

https://publications.lib.chalmers.se/records/fulltext/143602/local_143602.pdf

Modelling EBG surfaces using amended DB boundary conditions

There is an increasing interest in combining several antennas into a multi-function system, thus incorporating multiple frequency bands into a single antenna. Multi-band phased arrays are potential candidates for this purpose, allowing several frequency bands to operate from the same array aperture, i.e. aperture reuse. Such arrays may be realized by using compact narrowband elements in an array sufficiently sparse for intermediate compact elements operating at other frequencies to be embedded or superposed over the same array aperture. Hence, there is a need for miniaturized elements that are very small in terms of wavelength. The paper investigates miniaturized open-ended rectangular waveguides for use as array elements. We show that operating dielectric-loaded rectangular waveguide elements of an infinite planar array within the vicinity of the TEM frequency gives rise to the best transmission. In addition, it is seen that miniaturization in E-plane is better than in H-plane. For a large degree of miniaturization, the reflection coefficient is large and needs to be reduced by incorporating matching layers or similar. The results have been verified by using two independently developed codes. One of these has also been validated in other works.

Miniaturized dielectric-loaded rectangular waveguides for use in multi-frequency arrays

We present the statistics of the simulated received voltages on diversity antennas in line-ofsight and rich isotropic multipath environments. The two environments are compared for receiving antennas with random positions and orientations, producing a random line-of-sight. The antennas are canonical small antenna types such as an ideally omni-directional antenna, and incremental electric dipoles, magnetic dipoles and Huygens sources.

Per-Simon Kildal

Papers

Ka-band gap waveguide coupled-resonator filter for radio link diplexers

EuCAP 2013 in Gothenburg, Sweden: “An Impressive Success” [EurAAP Corner]

Modelling EBG surfaces using amended DB boundary conditions

Miniaturized dielectric-loaded rectangular waveguides for use in multi-frequency arrays

Study of Random Line-of-Sight Caused by Arbitrary User Positions and Orientations with Application to MIMO OTA Measurements of Wireless Devices