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.

Modern antenna technologies stimulated by the Arecibo radio telescope upgrade project 1984–1997

Abstract: The world's largest single-reflector radio telescope is located in Arecibo. Its Gregorian dual-reflector feed was inaugurated in 1997, representing an enormous improvement in terms of bandwidth (limited by that of a wide-angle corrugated horn) and aperture efficiency compared to using the previous line feeds of about 1% bandwidth. The inauguration was preceded by an upgrading project of more than 10 years duration, during which author of this paper was stimulated to get ideas of several other technologies that were further developed the decades thereafter. The present paper gives an overview of these technologies, and how they are related to the upgrade project: the Comhat antenna (a hat-fed reflector) originating from an initial theoretical model of the line feeds, semi-analytical reflector synthesis by ray tracing, wideband constant wide-beamwidth feed for paraboloids, canonical soft and hard surfaces, and gap waveguides.

Validation of uncertainty model for reverberation chamber measurements

Abstract: The reverberation chamber (RC) is basically a metal cavity, which is mechanically stirred to emulate a Rayleigh fading environment. It has been traditionally used for electromagnetic compatibility (EMC) [1]. For the past decade, it has found new applications for over-the-air (OTA) testing because of its capability to emulate Rich Isotropic Multipath (RIMP) [2]. Due to the complicated and time-varying boundary conditions, RC measurements are studied from a statistical point of view for both EMC and OTA applications. A statistical RC measurement is incomplete without the analysis of measurement uncertainty. As a result, the RC measurement uncertainty has been a popular research topic. Different approaches have been adopted in tackling the problem. Most of the studies (that are based on independent sample number e.g., [3]) offer limited insight into how to improve the measurement uncertainty. The authors have proposed an uncertainty model (referred to as Chalmers model hereafter) [4] that, for the first time, separates the stirred component and the unstirred one (i.e., the K-factor [5]), with the later being the residual error, that is, a small measurement uncertainty requires not only a large number of independent samples but also a small K-factor [4]. Based on this insight the measurement accuracy of the Bluetest RCs was significantly improved (see [4]) by introducing a metallic shield to block the line-of-sight (LOS) path. In order to validate the proposed uncertainty model, we proposed a nine-case-measurement uncertainty assessment procedure. That is, we repeat the same measurement sequence nine times, each time with a different height/orientation of the reference antenna on the turntable platform, i.e., the antenna on the platform is placed with three different heights and at each height it is placed with three different orientations. The height separation should be large enough (e.g., half-wavelength at the lowest frequency) to ensure independent measurements. (The half-wavelength is a rule-of-thumb for the correlation length [6], beyond which the correlation becomes negligible, in a well-stirred RC.) In order to validate the uncertainty model, we performed extensive measurement campaigns in four RCs (see Table 1) with different sizes and stirring mechanisms. Fig. 1 shows the estimated standard deviations (STDs) of the average power transfer functions from nine-case-measurement uncertainty assessment procedure together with the modeled STDs for the four RCs, respectively. The solid curves represent measurements and the dotted curves correspond to the model. Note that the measurement campaigns were performed with a 5-year span with the main intention to validate the uncertainty model in different RCs. Hence, different loading conditions, sample numbers, and frequency ranges were used. However, it is safe to conclude that the RTS90 has the best measurement accuracy, even though it is operating in a lower frequency range. Anyway, as can be seen from Fig. 1, the model agrees with the measurement for all cases. This validates the uncertainty model. At the conference we will present the Chalmers uncertainty model and describe the stirring sequences and chamber configurations of different RCs in details.

Comparing throughputs of 2×2 spatial multiplexing MIMO systems with and without CSI at the transmit side in rich isotropic multipath environments

Abstract: Multiple-input multiple-output (MIMO) systems are attracting more and more attention due to the need of high spectral efficiency. Simple yet accurate throughput models are highly desired for studying the MIMO performance. MIMO throughput models based on the threshold receiver have been studied in [1], [2]. Specifically, a single-input multiple-output (SIMO) throughput model based on the concept of the threshold receiver was presented in [1]. The SIMO throughput model was extended to MIMO systems with full spatial multiplexing in [2], where only the open-loop configuration is studied.

Planar eleven antenna as a wideband MIMO micro-base station antenna

Abstract: A new low-profile planar eleven antenna is designed as a wideband MIMO antenna for micro-base stations in future wireless communication systems. The design criterion is to minimize both the reflection coefficient and the ratio of the required average received power over the threshold for 95% of the total probability of detection (PoD) in the Rich Isotropic Multipath (RIMP) and random Line-of-Sight (RLOS) scenarios of both one-bit stream and two-bit stream. The design is performed via optimization with a genetic algorithm.

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.