Jean-Pierre Ghys

On the use of 3-D TEM cells for total radiated power measurements

Three-dimensional (3-D) TEM cells offer new issues in EMC immunity and emission testing, where the question of orienting the object under test is no longer raised. This paper starts by presenting the general concept of 3-D TEM cells and hybrid chambers followed by one of the first applications in measuring the total radiated power of devices under test. After a short background on emission measurements in TEM and GTEM cells, the second part of this paper considers a practical industrial case where the total radiated power of an electronic equipment is measured in a 3-D TEM prototype cell, and the results compared to those of TEM and GTEM cells. Finally, the repeatability and reproducibility between TEM, GTEM and 3-D TEM cells is studied and discussed.

4×4 MIMO channel sounding in tunnels for train-to-wayside communications

This paper presents MIMO channel sounding measurements performed in the underground road tunnel of Roux, in south of France, at 5.8 GHz. Different scenarios for antennas (spacing and polarization) and moving vehicles speeds were carried out in the tunnel. The aim was to be as close as possible to scenarios one can encountered in railway environments. From these measurements, MIMO channel matrices are computed, in order to determine the correlation level of the channel and its capacity along the tunnel, according to different antenna spacing and polarization.

On the use of three-dimensional TEM cells for total radiated power measurements

Three-dimensional TEM cells offer new issues in EMC immunity and emission testing, where the question of orienting the object under test is no longer raised. This paper starts by presenting the general concept of 3-D TEM cells and hybrid chambers followed by one of the first applications in measuring the total radiated power of devices under test. After a short background on emission measurements in TEM and GTEM cells, the second part of this paper considers a practical industrial case where the total radiated power of an electronic equipment is measured in a 3-D TEM prototype cell, and the results compared to those of TEM and GTEM cells. Finally, the repeatability and reproducibility between TEM, GTEM and 3-D TEM cells is studied and discussed.

Methods of target recognition for UWB radar

With the growth of embedded components (GPS, radar, cameras…), road vehicle becomes more and more intelligent and reassuring.

Analysis of the coupling path between transient EM interferences produced by the catenary-pantograph contact and on-board railway communication antennas

An in-depth analysis of the electromagnetic interferences generated by trains requires a better understanding of specific railway interference sources. Interferences due to the losses of contact between catenary and pantograph are among them. This paper presents a modeling methodology proposed to analyze the effect of pantograph arcing on GSM-R antennas located on the train roof. The model was developed using the CST™ microwave studio tool. Comparisons were performed with experimental results to assess the quality of the simulation results. Finally, an analysis was carried out in order to discriminate the couplings between the GSM-R antenna and the different components of the model.

EFFECT OF MULTIPATH ON AVAILABILITY OF GPS SATELLITES

One of the main drawbacks of satellite localization systems is the lack of visibility experienced in high masked environments such as dense urban areas or railway cuttings. As a consequence, the number of correctly received satellites within the constellation could be drastically reduced. This implies a degradation both on the position calculation accuracy and on system availability. In this paper, we present the theoretical and experimental results we have performed, related to the satellite signal propagation analysis in case of NLOS reception. We show that both diffraction and signal received after more than one reflection can be neglected in the localization computation. Therefore, we introduce these conclusions in a tool we have developed, that predicts the constellation availability along a trajectory. By taking into account the satellite signal propagation characteristics, we are able to : - define which satellite should be excluded from the location calculation, - predict an estimated error on the location and give a measurement confidence interval, - define the areas which suffer from a lack of radio electric coverage, in order to eventually deploy augmentation solutions to complete the localisation system.

A time-domain diagnostic method for emission measurements in TEM cells

Emission testing techniques using TEM cells are currently based on power measurements at their port(s) in the frequency-domain. Spectrum measurements do not give directly phase information and therefore only offer partial information on the electromagnetic emission of an equipment under test (EUT) such as the total radiated power. This drawback often leads to difficulties in interpreting the emission results in order to determine precisely the origins of radiation within the EUT and to improve its design. This paper presents a new diagnostic method based on time-domain emission measurements using TEM cells in order to determine the origins of radiation within an EUT Unlike spectrum measurements, time-domain measurements can offer full information on radiation, and by correlation with the known currents in the EUT, can help pin-pointing the contributors within the EUT responsible of the highest emission levels.

MIMO channel characterization in subway tunnel for train-to-wayside applications

The demand for robust and high data rate wireless transmissions in tunnel leads to evaluate the impact of MIMO and diversity techniques over the channel performance in these types of environments. This paper presents a 4×4 MIMO channel sounding measurement campaign performed in the tunnels of the FGC (Ferrocarrils de la Generalitat de Catalunya) metro in Barcelona, at 5.8 GHz. Different configurations were tested with different antenna polarization and orientation in the tunnel. From these measurements, MIMO channel matrices are computed, in order to determine the correlation level of the channel and the MIMO channel capacity along the tunnel.