Marc Pous

Full-Spectrum APD Measurement of Transient Interferences in Time Domain

Radiated transient interferences produce severe errors to digital communication systems. Conventional measurements defined in the electromagnetic compatibility (EMC) standards are not sufficient to predict the impact of this impulsive noise on the quality of a digital system, as measurements were originally defined to protect analogue communication systems. Measurement detectors and methods based on reaching the statistical of the interference have been studied as the best option to evaluate transient interferences. For a properly EMC emissions evaluation, an amplitude probability detector (APD) has been recommended as the best option, since APD results have been correlated with bit error probability. However, carrying out APD measurements using electromagnetic interference (EMI) receivers has strong inconvenience. One of the main limitations is that measurement can only be performed with the preset filters available at the EMI receiver, which sometimes are different from the communication bandwidths causing an incorrect estimation on the degradation produced. Another restriction is the elapsed time needed to acquire the statistical APD measurement at each frequency band. This document presents a methodology to obtain the APD measurement at any frequency band employing two single time-domain oscilloscope captures. The developed measurement method makes it possible to obtain the APD at any frequency band achieving as good results as the ones acquired from EMI receivers. To show the effectiveness of the time-domain method, an exhaustive validation study is presented, in which white Gaussian noise and several impulsive interferences are evaluated at frequencies from 50 MHz up to 1 GHz.

Decomposition of Electromagnetic Interferences in the Time-Domain

Electromagnetic interferences are potentially very complex signals formed by the superposition of transient (broadband) and continuous wave (narrowband) components with significant randomness in both amplitude and phase. Decomposing the electromagnetic interference measured in the time domain into a set of intrinsic mode functions is useful to gain insights of the process that generates the interference. Evaluating the intrinsic mode functions contributes to improving the measurement capabilities of the time-domain electromagnetic emissions measurement systems based on the general-purpose oscilloscopes. In this paper, a combination of techniques that includes empirical mode decomposition and transient mode decomposition is used to separate the main components of complex electromagnetic disturbances. This approach requires no prior information on the spectral content of the measured EMI and it does not perform a domain transformation. Examples of electromagnetic interference decomposition verify the effectiveness and the accuracy of the proposed approach. Finally, a discussion on the advantages, practical applications, limitations, and drawbacks of the described techniques is addressed.

On the Statistical Properties of the Peak Detection for Time-Domain EMI Measurements

This paper presents a discussion on the inherent characteristics of the measurements performed with time-domain electromagnetic interference measurement systems in regards of the detection of the maximum emissions levels. In that sense, some relevant statistical properties of the frequency components of the maximum emissions levels in the amplitude spectrum are investigated using the extreme value theory to provide a model based on the Gumbel probability distribution and estimates for its parameters, expected value, variance, and Cramer-Rao bounds. The results suggest that using the expected maximum value of the emissions levels instead of the just the observed maximum value improves the measurement repeatability and also reduces the uncertainty in the results. This paper presents an additional insight measure that enhances our understanding of the statistical behavior of the measured EMI and of the time-domain measurement process itself.

Improving time-domain EMI measurements through digital signal processing

This article is intended to provide a set of recommended practices for improving of the Time-Domain EMI measurement systems by means of digital signal processing. We have focused on two major aspects: the optimal configuration settings of the direct measurement equipment and the deployment of algorithms to process the measurement result. In that sense, we believe that general purpose time-domain instruments, as oscilloscopes, can be successfully used as an alternative hardware to measure EMI, since they provide accurate and reliable results, surpassing the conventional frequency-domain approach when transient disturbances are present.

Prediction of the impact of transient disturbances in real-time digital wireless communication systems

In this paper the simulation methodology has been useful to establish the effect of a transient interference coupled to a digital communication system. An RFID system according to ISO 14443 type B standard is interfered by transient interference according to EN 61000-4-4 standard producing decision errors. The usage of the software tools employed to analyze the distortion of digital communication systems in convergence of the EM simulation software is a powerful methodology to quantify the degradation of a real digital communication system.

A measurement system for radiated transient electromagnetic interference based on general purpose instruments

This paper presents a measurement system intended to be used to assets the radiated electromagnetic interference (EMI) in both time and frequency domains. In order to keep the measurement setup as accessible and practical as possible, the direct measurements are recorded with a general purpose digital oscilloscope and processed with a commonly available personal computer. The measurement system was validated for radiated emissions testing using well-known, controlled transient and continuous signals emulating typical interferences. The results are in satisfactory agreement with those provided by a conventional EMI receiver for different types of detectors. The proposed approach shows that, currently, it is possible to implement a timesaving, accurate and generally inexpensive time domain measurement system for radiated emissions that is capable to overcome the limitations of the superheterodyne EMI receivers regarding the measurement of discontinuous electromagnetic disturbances and also able to provide additional enhanced features to evaluate and troubleshoot EMI problems.

Transient perturbation analysis in digital radio

This paper presents a new simulation methodology to study the effect of radiated transient disturbances on digital communication systems. The procedure is divided in two stages. In the first one, FDTD numerical simulation is used to determine the transient levels coupled to the antennas. In the second stage, these levels are analyzed by means of a signal processing simulation software to determine the degradation caused in the system. The procedure is applied to a DAB system in car when a radiated interference is generated by a transient in a vehicle cable. The results show that the amplitude of the radiated transient coupled signal is a key parameter, but it is also essential to take into account other parameters such as burst duration and frequency.

Validation of low-level, high-frequency transient FDTD simulation with radiated field measurements

Validation of numerical simulation results for low-level, high-frequency transient radiated EMC signals is difficult because of the limitations of time domain measurement instruments. A measurement method combining the sensitivity of a RF spectrum analyzer and the time domain abilities of a digitizing oscilloscope is used to validate FDTD simulations of a fast transient coupled between two antennas inside a car.

Measurement and Evaluation Techniques to Estimate the Degradation Produced by the Radiated Transients Interference to the GSM System

A common source of noise for digital communication systems is the radiated transient interference. As an example, it has been reported that the degradation is produced to the Global System for Mobile (GSM)-Railway signaling system when the impulsive noise is generated by sparks caused by the discontinuity between the catenary and the pantograph. Concerning the measurement and evaluation procedures defined in the electromagnetic compatibility standards, they are not suitable for these types of transient disturbances. Therefore, new techniques must be developed to determine, with a high confidence level, the degradation that impulsive noise will produce in communication systems. In this paper, novel time-domain measurement procedures are carried out to acquire transient interferences generated by sparks properly. Moreover, two different evaluation methodologies, employing base-band simulation and amplitude probability distribution detector, are used to analyze the impact of the disturbance applied into a GSM system interference scenario. Finally, the results obtained with the developed methodologies are successfully compared with a reference measure where the GSM downlink channel quality is monitored by a mobile station test unit.

SIVA UAV: A Case Study for the EMC Analysis of Composite Air Vehicles

The increased use of carbon-fiber composites in unmanned aerial vehicles is a challenge for their EMC assessment by numerical solvers. For accurate and reliable simulations, numerical procedures should be tested not only for individual components, but also within the framework of complete systems. With this aim, this paper presents a benchmark test case based on experimental measurements coming from direct-current injection tests in the SIVA unmanned air vehicle, reproduced by a numerical finite-difference-time-domain solver that employs a new subgridding scheme to treat lossy composite thin panels. Validation was undertaken by applying the feature selective validation method, which quantifies the agreement between experimental and numerical data.