Robert Vogt-Ardatjew

On-Site Radiated Emissions Measurements in Semireverberant Environments

Radiated emission tests are generally performed in either free space, reflection-free environments, such as an open area test site or semi- or full-anechoic chambers, or in reverberation chambers. This paper describes measurements in semireflecting environments such as an office, a workshop of a large industrial apparatus or installation. The objective is to develop test methods and associated correction factors and uncertainties for measurements which are performed on-site, near large industrial apparatus which cannot be moved to an EMC laboratory. The measurement technique is based on reverberation chambers and tools such as insertion loss, quality factor, as well as a goodness of fit test were used to perform the test site analysis. The advantages and drawbacks of on-site measurements of large apparatus are discussed. A simplified, but not limited to perfect reverberation chambers, method of finding the measurement uncertainties was used to calculate the errors associated with imperfect reverberation and field uniformity, as well as the influence of noise and equipment nonlinearities. The results are given in form of a guideline, concluding that such measurements are possible.

Accurate Experimental Field Mapping in the Close Vicinity of a Pyramidal Absorber Using the Monostatic Optically Modulated Scatterer Technique

The paper presents the application of an underrated tool, monostatic modulated scatterer technique (MST), for measuring electromagnetic field distribution in the vicinity of dielectric objects of complex shape. Monostatic MST, using optically modulated scatterers, allows field distribution to be measured with minimal distortion. A unique example has been shown for measuring the electromagnetic field distribution around the pyramidal absorber, as well as the measurement between its adjacent pyramids. The test results obtained were verified by computer simulation. Very good conformity of measurements and calculations was achieved. The influence of the finite size of the scattering probe on the accuracy of the determination of the measured field strength is also shown.

Intentional electromagnetic interference through saturation of the RF front end

There is an increasing use of wireless applications in todays society. A big disadvantage of wireless communication is the high vulnerability to denial-of-service (DoS) attacks. Intentional electromagnetic interference can saturate, and thereby block and desensitize, the wireless receiver. This mechanism of causing a DoS is different from well-studied jamming attacks. It is important to determine and quantify saturation levels of a receiver. The saturation is quantified by the 1-dB compression point, P1-dB. An experimental method is presented that can determine P1-dB over a wide frequency band in a fast and accurate way. Results show the need for a high quality front door filter to be robust against out-of-band interference.

The effect of magneto-dielectric absorbing coating on unsymmetrical antenna cables

It is well known that the presence of conductive cable can cause significant changes in field distribution as well as affecting antenna characteristics. This paper focuses on the experimental estimation of the usability of special absorbing coating on antenna cable in order to minimize its influence on the measured fields. The experimental analysis has been conducted in both anechoic and reverberant environments.

On-road magnetic emissions prediction of electric cars in terms of driving dynamics using neural networks

This paper presents a novel artificial neural network (ANN) model estimating vehicle-level radiated magnetic emissions of an electric car as a function of the corresponding driving pattern. Real world electromagnetic interference (EMI) experiments have been realized in a semi-anechoic chamber using Renault Twizy. Time-domain electromagnetic interference (TDEMI) measurement techniques have been employed to record the radiated disturbances in the 150 kHz-30 MHz range. Interesting emissions have been found in the range 150 kHz-3.8 MHz approximately. The instantaneous vehicle speed and acceleration have been chosen to represent the vehicle operational modes. A comparative study of the prediction performance between different static and dynamic neural networks has been done. Results showed that a Multilayer Perceptron (MLP) model trained with extreme learning machines (ELM) has achieved the best prediction results. The proposed model has been used to estimate the radiated magnetic field levels of an urban trip carried out with a Think City electric car.

Electromagnetic Fields in Reverberant Environments

The phenomenon of resonating electromagnetic (EM) fields has been commonly and successfully exploited in reverberation chambers (RC) for the purpose of electromagnetic compatibility (EMC) testing, as well as modeling multipath environments. Although largely successful, the currently used statistical models allow for a certain degree of freedom, especially with regard to defining the extreme field strengths, which are also the main cause of electromagnetic interference (EMI). Furthermore, some actual multipath, enclosed environments such as airplane fuselages, ships, or even building interiors, can unintentionally possess the ability to create enough strong reflections so that the resulting resonating EM field within them resembles the field inside a dedicated RC. The initial step made in this thesis focuses on introducing REs as environments sharing multiple aspects of EM field shaping with RCs. The results indicate a possible similarity to a referential RC analyzed alongside. Furthermore, due to the difficulty of collecting large amounts of data and parameter isolation in the REs, two dedicated chambers: a classical RC and the vibrating intrinsic reverberation chamber (VIRC), have been analyzed as candidates allowing to simulate an RE in laboratory conditions. The search of maximum field strengths in REs has been performed by exploiting the capability of the VIRC to efficiently generate large amounts of independent samples. Performing very long measurements in the VIRC allows to obtain the desired results with very high repeatability, while giving space for parameter isolation. The measurement results obtained outside the laboratory conditions allowed to formulate a method of performing on-site emissions testing. Although performed in imperfect REs, a modified RC standard technique has been successfully applied, concluding that such an approach is possible and recommended. The final topic of the thesis discusses a creation of a simplified macro-parameter model of field coupling to cables when neither the exact cable geometry, nor the coupling field is known. Instead of focusing on precision, this investigation aims at finding any similarities, possibly allowing to avoid the difficulties related to the very sensitive description of a non-uniform transmission line, exploiting the mixed randomness of the line geometry and the multipath field excitation.

Experimental plane wave and random field coupling to uniform and non-uniform transmission lines

This paper aims at the investigation of similarities and differences between the coupling mechanisms of an unknown electromagnetic field to a transmission line routed in an unknown way. As opposed to many other studies, this work is focused on the creation of an experimental, simplified, statistical, macro-parameter based model to be used as a quick “rule of the thumb” solution. The measurements have been performed in a GTEM cell and in a reverberation chamber, creating a plane wave and random illumination, with uniform and non-uniform transmission lines. It has been shown that the variation of results of different lines with same macro-parameters, placed in multipath environment becomes lower for higher frequencies, and an asymptotic approach is reasonable. The worst case, i.e. strongest coupling, scenario is extracted and compared for two different field excitation mechanisms. Then, the error is considered when simplifications are made, like approximating a non-uniform line with a straight one, or the threat underestimation if only one cable geometry is measured.

Statistical analysis of three different stirrer designs in a reverberation chamber

A reverberation chamber (RC), is an economical facility in EMC, because it allows many directions for illumination an object with a higher field strength compared to conventional techniques, for the same input power. For emission measurements there is no need for moving an antenna. The field uniformity and statistical behaviour of the field are important in a RC. This paper presents an evaluation of the performance for three different stirrer designs inside a 1.00 m × 1.30 m × 1.50 m reverberation chamber. The evaluation was done in the frequency range from 300 MHz to 1000 MHz using both simulation and measurement results.

Response time of electromagnetic field strength probes

Modern signals in for instance wireless communication systems and radars use very complex modulation with high peak-to-average ratio. Other signals, such as in reverberation chambers with mode stirring, vary very fast with a high dynamic range. Conventional probes, using thermocouples or diode detection, show wrong measurement results due to the slow response time of the detector or the analog-to-digital converter, or the limited dynamic range of the detector. These response times are often missing in data sheets, and in case they are listed the numbers are not always correct. This paper describes pulse response experiments performed with a radiation hazard meter, a diode detector, several commercial field strength probes and probes using logarithmic detectors.