Per-Simon Kildal

Bio: Per-Simon Kildal is an academic researcher from Chalmers University of Technology. The author has contributed to research in topics: Antenna (radio) & Electromagnetic reverberation chamber. The author has an hindex of 60, co-authored 504 publications receiving 13470 citations. Previous affiliations of Per-Simon Kildal include SP Technical Research Institute of Sweden & Norwegian Institute of Technology.

Radiation Q and radiation efficiency of wideband small antennas and their relation to bandwidth and cut-off of spherical modes

Abstract: Resonators are traditionally characterized by their quality factor Q, which is inversely proportional to the relative bandwidth. Small antennas are often resonant, so they can be characterized by a Q, except for the fact that the correct quality measure of an antenna is rather the inverse Q. i.e. the relative bandwidth. Still, it has become common to study fundamental size limitations of small antennas in terms of a so-called radiation Q (or antenna Q). The paper explains how this intrinsic radiation Q relates to: i) the bandwidth- efficiency product of small single-resonance-type antennas, ii) the gradual cut-off of spherical waves for wideband gradual-transition-type small antennas, and iii) the number of resonances needed to cover a certain frequency band for wideband multiple-resonances-type small antennas. The paper also introduces one intrinsic radiation Q for basic single TE and TM spherical mode sources, and another for combined TE and TM sources.

Multipath characterization of antennas for MIMO systems in reverberation chamber including effects of coupling and efficiency

Abstract: We describe how to measure the radiation efficiency, correlation, diversity gain and capacity of a six-monopole antenna array in a reverberation chamber in order to characterize it by these parameters for a MIMO system. We show how these measurements can be used to find the channel capacity when a particular antenna array is used in a MIMO system. We also explain how numerical modeling of the MIMO array in a commercial code can be used to find the channel capacity.

Measurement of Embedded Element Efficiencies of Wideband Dense Arrays in Reverberation Chamber

Abstract: The paper describes how coupling efficiencies in dense arrays can be measured in a reverberation chamber. This is much faster than measuring S-parameters between all element ports and calculating the coupling efficiencies from these. Results are presented between 2 and 6 GHz for an array of 144 Vivaldi elements developed by ASTRON for use as a technology demonstrator for SKA (Square Kilometer Array). The results include coupling efficiencies for singly-excited elements (referred to as embedded element efficiencies), as well as for three different focal-plane-array excitations. The embedded element efficiencies are compared with an approximate formula derived from classical papers. The results show significant efficiency losses at low frequencies. (5 pages)

An arrangement for interconnection of waveguide structures and a structure for a waveguide structure interconnecting arrangement

Abstract: The present invention relates to a arrangement (100) for interconnection of waveguide structures (10,20) or components comprising a number of waveguide flange adapter elements (100) comprising a surface of a conductive material with a periodic or quasi-periodic structure (15) formed by a number of protruding elements (115) arranged or designed to allow waves to pass across a gap between a surface around a waveguide opening (3) to another waveguide opening in a desired direction or waveguide paths, at least in an intended frequency band of operation, and to stop propagation of waves in the gap in other directions. It comprises means allowing interconnection with a waveguide flange or another waveguide flange adapter element without requiring electrical or conductive contact and assuring that the gap is present between the at least one surface (15) formed by periodically or quasi-periodically arranged protruding elements (115) and a surface around a waveguide opening of the other waveguide flange (20), hence assuring that the surface (15) formed by the periodically or quasi-periodically arranged protruding elements (115) is not in direct mechanical contact with the other, opposite, interconnecting, waveguide flange (20).

Useful Physical Images and Algorithms for Vector Dyadic Green's Functions [Wireless Corner]

Abstract: This article gathers useful, simple algorithms and their physical interpretations for field solutions from incremental sources in three-dimensional (3-D) spatial, two-dimensional (2-D) spectral, and one-dimensional (1-D) spectral domains. The interpretations of the 1-D spectral Green's functions are visualized in space as fields from current sheets, tubes, and shells for the planar, circular cylindrical, and spherical cases, respectively. A joint algorithm is presented for solving the multilayer case for all three cases. Similarly, field problems involving cylindrical objects or bodies of revolution (BOR) are structured into spectrums of 2-D spatial solutions from line sources and ring sources, respectively. The formulations and physical images are pedagogical and open up for new creative ways of teaching electromagnetic (EM) field theory as well as structuring numerical algorithms for field solutions that take known symmetries into account. It is also shown that the 3-D spatial Green's functions can be approximated to improve physical interpretation by omitting higher-order 1/r terms when r > 2λ.

High-impedance electromagnetic surfaces with a forbidden frequency band

Abstract: 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.

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

Abstract: 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.

Photonic crystals

Abstract: 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.

Transformation optics and metamaterials

Abstract: 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.

The 2017 terahertz science and technology roadmap

Abstract: 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.