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

Determination of Measurement Uncertainty of Different Reverberation Chambers

Professors Zirath and Kildal’s groups at Chalmers have started a cooperation on developing a spatial quasioptical grid amplifier. Initially most work is done by guest researcher and Master students. The waveguide components are studied in Kildal’s group, whereas the active grid is being studied in cooperation between Zirath’s group and Dr Weikle’s group in Virginia. The present paper describes the initial study of the waveguide components, involving the development of a hard horn transition from a standard waveguide to a quadratic quasi-TEM hard waveguide.

https://www.ep.liu.se/ecp/008/posters/039/ecp00839p.pdf

Study of Cavity Resonances in Quasioptical Grid Amplifier with Hard-walled Waveguide Section

http://ieeexplore.ieee.org/iel6/8250/25855/01148321.pdf

An axial correction to the computed directivity of parabolic reflector antennas

The possibility of reducing the radiation from mobile phones into the human body by using a directive antenna is studied. The antenna analyzed is a Huygen's source, that is, a theoretical directive antenna consisting of an incremental electric dipole perpendicular to an incremental magnetic dipole. The relative power absorption is calculated for three different models of the human head. The simplest head model is a lossy dielectric half space, a somewhat less rough model is an infinitely long lossy cylinder of circular cross section and the most exact head model is a homogeneous lossy dielectric sphere. A comparison with a Hertzian dipole, i.e. an incremental electric dipole, at the same positions is done. The different head models are used in order to investigate to what extent it is possible to simplify the model of the human head while still getting useful results. The results show that the relative power absorption for the Huygen's source is substantially lower than that for a Hertzian dipole. When the antenna is placed 2 cm from a lossy dielectric homogeneous sphere of radius 10 cm, the relative absorption is 5 dB lower for the Huygen's source compared to a Hertzian dipole. It is also shown that when the antenna is placed close to the head, the results for the different head models are fairly similar, especially when the antenna is a Hertzian dipole.

Radiation From Directive Antennas Close to Human Tissue

The 3rd Generation Partnership Project (3GPP) has provided successful reports and specifications for Long Term Evolution (LTE). The LTE system is the so-called 4G system. A major difference between LTE and its 3G predecessor is that orthogonal frequency division multiplexing (OFDM) and multiple-input multiple-output (MIMO) techniques are employed in the LTE system, thanks to which a much higher throughput can be achieved in the LTE system. To evaluate LTE with end-user experience, over-the-air (OTA) testing of the performances of LTE devices is needed. Among the MIMO-OTA testing techniques, the reverberation chamber (RC) based OTA testing system [1, 2] seems the most promising candidate due to its fast and repeatable measurement. Despite the high efficiency of the RC-based OTA measurement, a theoretical model of the OTA measurement to complement measurement is desired. With throughput being the most interesting performance metric of LTE OTA testing, a throughput model based on the threshold receiver concept has been proposed in [3]. The throughput model is valid for both diversity and spatial multiplexing cases [4]. The reverberation chamber was first used for EMC measurements, i.e. measuring the effects of undesired radiation. Then, measurement uncertainty was not important. In this paper we describe how it is used for measuring the effects of desired radiation, and then we of course would like to have measurement uncertainties smaller than 0.5 dB in order to distinguish good from bad LTE devices. This is possible with the latest RC developments [5]. Fig. 1 shows the modeled and measured LTE system with different system bandwidth B s under different channel coherence bandwidths B c . Note that the coherence bandwidth in the RC can be controlled by loading the chamber with different amounts of lossy objects [6], whereas, in the simulation, it is taken into account by generating independent OFDM subcarriers [3]. As can be seen, the throughput model well predicts the measurement. In the final presentation, we will present the throughput model in details. We will also present LTE throughput measurements and modeling for different LTE MIMO configurations, the relationship between Total Isotropic Sensitivity (TIS) and throughput, and the interpretation of throughput as a Probability of Detection (PoD).

https://www.ursi.org/Proceedings/ProcGA14/papers/ursi_paper1746.pdf

Per-Simon Kildal

Papers

Determination of Measurement Uncertainty of Different Reverberation Chambers

Study of Cavity Resonances in Quasioptical Grid Amplifier with Hard-walled Waveguide Section

An axial correction to the computed directivity of parabolic reflector antennas

Radiation From Directive Antennas Close to Human Tissue

Over-the-air LTE measurements in the reverberation chamber