Mats Bäckström

Experimental Investigation and Mathematical Modeling of Design Parameters for Efficient Stirrers in Mode-Stirred Reverberation Chambers

In this paper, we have investigated the design parameters for efficient stirring in reverberation chambers. We have measured the efficiency of the stirrer in terms of the lowest possible frequency for which it gives a certain number of uncorrelated samples. Rotating stirrers, when rotated about their axes, generate cylindrical volumes. The impact of a change of the stirrer diameter is approximately cubic compared with the change of the stirrer height. The efficiency of stirrers that are translated is proportional to the stepping increment and to the square root of the area of projection of the stirrer on a plane orthogonal to the direction of translation

Vulnerability of European Rail Traffic Management System to Radiated Intentional EMI

In this paper, the vulnerability of the future electrified railway system in Europe from a high-power microwave (HPM) source is investigated. The scenario of in-band disturbances radiated toward a GSM-R antenna and damaging the connected communications system is evaluated for different classes of HPM sources and situations. The minimum realistic distances for the different HPM sources from the antenna to cause permanent damage is shown, and the severity of threat from the different sources is discussed.

Overview of four European high-power microwave narrow-band test facilities

This paper presents an overview of the key high-power microwave (HPM) narrow-band source technologies and their related HPM open-area radio-frequency (RF) test capabilities within four European counties (France, Germany, Sweden, and the U.K.). The test facilities are described and a brief description of further developments is given covering both power limitations and recent research interests.

Methodology for Classifying Facilities With Respect to Intentional EMI

It is argued that it is the intent behind the electromagnetic interference in intentional electromagnetic interference (IEMI) that causes problems to large distributed systems and facilities even if they are designed by traditional zoning concept rules. Hardening such facilities against IEMI requires a correspondence between the electromagnetic zone boundary and the physical access control boundary. The three characteristics of a facility, the accessibility, susceptibility , and consequence, are discussed in the context of vulnerability to IEMI. A methodology for classification of facilities with respect to IEMI is presented.

Semi-empirical modeling of apertures for shielding effectiveness simulations

A novel method to include models of complex apertures into the finite-difference time-domain (FDTD) method is presented. Instead of resolving the geometrical details of the aperture, the aperture is treated as a magnetic dipole. The properties of the magnetic dipole moment are determined using the measured transmission cross section of the aperture. This semi-empirical model permits inclusion of complex apertures in FDTD simulations where the smallest dimension of the aperture is only a fraction of the FDTD cell size. Two types of complex apertures positioned in the top panel of a realistic enclosure have been modeled using the semi-empirical model in FDTD. Comparisons between simulated and measured shielding effectiveness of the enclosure are presented, and the results show that complex apertures can indeed be represented by simple magnetic dipoles in shielding effectiveness simulations.

Susceptibility of Civilian GPS Receivers to Electromagnetic Radiation

Civilian handheld global positioning system receivers were tested for their susceptibility against radiated electromagnetic disturbances of different characteristics and field levels. This susceptibility data were compared to the existing electromagnetic compatibility (EMC) immunity requirements for electronic devices. Some of the receivers were disrupted by continues waves at in- as well as out-of-band frequencies, at field levels far below the existing EMC requirements. The possible reason for this is discussed. In general, due to the ever-growing use of commercial-off-the-shelf equipment even for critical functions, certificates of conformity to current EMC requirements may be inadequate.

Propagation of UWB Transients in Low-Voltage Installation Power Cables

This paper investigates the propagation of subnanosecond rise time (ultra wideband) voltage transients in low-voltage installation power cables. Experimental results are compared to simulations. It is concluded that the main mode of propagation of differentially injected transients in low-voltage installation power cables is transverse electromagnetic mode. Also, such transients would spread relatively unattenuated to any load or junction in the power system, received power primarily only limited by the impedance mismatches causing reflections. The effects of different types of bends in the cable have been studied. The study was conducted as a part of an assessment of the susceptibility of civilian facilities to intentional electromagnetic interference.

Numerical simulations as a tool for optimizing the geometrical design of reverberation chambers

The finite difference time domain (FDTD) method is used to simulate the electro-magnetic field in a reverberation chamber. By including conductivity and thickness of the walls in our model a good agreement with measurements is found. With help of the FDTD numerical computation program it is shown that by introducing wall mounted diffusers the minimum operating frequency of the reverberation chamber could be lowered.

Propagation of UWB Transients in Low-Voltage Power Installation Networks

In this paper, the propagation of ultra-wideband (UWB) transients through different types of junctions of low-voltage power cables and one real power network of a building were investigated. For the laboratory test, it was seen that the main mode of propagation in the cables and through the junctions tested is transverse electromagnetic (TEM). The received voltage could thus be, within a small error, estimated from transmission-line theory. The main cause for decreased voltage received at the loads of the branches of the junctions is reflections due to impedance mismatch of the junctions. Large voltages can be delivered to many unprotected loads connected to the junctions. UWB transients were also injected into a residential house using a power outlet available on the outside wall of the house. It was seen that the complexity of this network creates deviation from the TEM mode. However, relatively large voltages were still received at the various outlets inside the house. It is recommended that power outlets or lamp sockets outside buildings are controlled from inside using two-pole switches that reduce the received voltage to reduce the risk of conducted intentional electromagnetic interference.

Microwave breakdown in slots

The properties of microwave-induced breakdown of air in narrow metallic slots are investigated, both theoretically and experimentally, with emphasis on factors important for protection against transmission of incident high-power microwave radiation. The key factors investigated are breakdown power threshold, breakdown time, peak-leakage power, and total transmitted energy, as functions of incident pulse shape and power density. The theoretical investigation includes estimates of the electric field intensification in narrow slots and basic breakdown plasma modeling. New results important for application to the high-power microwave field, such as the influence of pulse shape on breakdown time and peak-leakage power, are presented. The experimental investigation comprises a set of slot breakdown experiments at atmospheric pressure, which are analyzed to extract key parameters, such as transmission cross section, breakdown time, peak leakage power, and transmitted energy. The experimental data is compared and shown to be in good agreement with results obtained in the theoretical investigation.