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.

The PMC-Amended DB Boundary - A Canonical EBG Surface

Abstract: Replacing realistic materials and structures by their ideal counterparts, canonical surfaces, is of great interest for initial and conceptual electromagnetic (EM) studies. The recently introduced DB boundary is defined by a set of simple boundary conditions forcing the normal components of the D- and B- fields to be zero at the boundary. We show that this DB boundary produces many 2-D scattering results that are similar to how practical so-called electromagnetic bandgap (EBG) surfaces behave within the bandgap. Still, it is not directly useable as a canonical EBG surface, because, as we demonstrate in this paper, it is incomplete, creating an anomaly for normal incidence which causes unphysical field solution for 3-D field problems. We have removed this anomaly by introducing the PMC-amended DB boundary. This works in the same way as a practically realized EBG surface for both 2-D and 3-D problems within the bandgap, and is therefore a canonical EBG surface.

A formula for efficient computation of radiation from a current source in proximity to cylindrical scatterers

Abstract: A systematic and efficient two-dimensional method is presented for calculation of the three-dimensional radiation field from current sources which are located in proximity to long cylindrical scatterers. The method is applied to the calculation of the isolated-element pattern of a linear array of crossed dipoles (i.e., current sources) mounted above a long and narrow ground plane. Computed and measured results are given. The results are subsequently applied to the problem of prediction of the radiation characteristics of a cylindrical reflector antenna fed by such a linear array.

Gaussian vertex plate improves return loss and far-out sidelobes in prime-focus reflector antennas

Abstract: Vertex plates are commonly used to improve the return loss of primary-fed reflector antennas. We propose a new type of vertex plate with a Gaussian thickness profile that gives lower far-out sidelobes of the radiation pattern of the reflector antenna than the standard vertex plate with constant thickness. We derive the dimensions of this vertex plate needed to cancel the field at the focus of the reflector. We apply the design rules to improve the return loss (RL) of a primary-fed reflector with hat feed, and simulate it by using a computer code based on the finite-difference time-domain (FDTD) technique. The results verify the improvements of the radiation pattern obtained by using a Gaussian vertex plate rather than a standard one. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 125–129, 1999.

Alternative ridge gap waveguide design using a mushroom-type EBG surface

Abstract: The new proposed ridge gap waveguide can be implemented with different types of periodic surfaces. In this manuscript we have shown how to use the mushroom-type EBG surface to this aim besides the previously used “Fakir's bed of nails”. The bandgap of the periodic structure inside the parallel plate gives the upper limit of the band of operation of the gap waveguide, being the distance to the upper plane or gap, a key parameter for the bandwidth. In both geometries, a reduction in this gap means a significant increase on the bandgap of the structure. Nevertheless, both structures have a bandwidth which is large enough for most of the applications, even if larger gap size values are considered. Due to its physical realization and volume, the pin surface is more suitable for high frequencies whereas the mushroom-type EBG surface could be used in lower frequency ranges.

Accuracy of antenna input reflection coefficient and mismatch factor measured in reverberation chamber

Abstract: It has previously been shown that radiation efficiency and input reflection coefficient S 11 fs of small antennas in free space can be obtained from measurements in reverberation chamber. The S 11 fs is obtained by so-called complex stirring of the S11 measured when the antenna is in the chamber. In the present paper it is shown that the accuracy of S 11 fs can be very good even for larger directive antennas at high frequency provided additional complex frequency stirring is applied. The corresponding deterioration loss in frequency resolution is small at high frequency, in the relative sense. The presented S 11 fs results match results measured in anechoic chamber down to −40 dB.

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.