2007 ieee international symposium on electromagnetic compatibility

18EMC <strong>2007</strong> ADVANCE PROGRAMpredicted the general statistical distribution of the complex reflectioncoefficient S11 of a test port connected to a transmitting antenna, butone measure of the variation was off by a factor of two. We eventuallytraced the increased variability to enhanced backscatter, in whichreflections back in the direction of the source antenna tend to be largerthan reflections in any other direction. Enhanced backscatter is aphenomenon generally associated with remote sensing, especiallyrelated to random media. We give general explanations of this effectbased on a simple ray-optics model.New Hybrid Mode-stirring Technique for Shielding EffectivenessMeasurement of Enclosures Using Reverberation ChambersSandra Greco; and Maria Sabrina Sarto, — University of Rome “LaSapienza”This paper presents a new method for the measurement of the shieldingeffectiveness of “small” enclosures. The technique implements ahybrid mode-stirring technique on nested reverberation chambers.The mismatching of the antenna radiating inside the enclosure undertest is taken into account.Sensitivity Analysis of a Reverberation Chamber WithRespect to Tuner SpeedsVignesh Rajamani; Charles Bunting; and James West, — Oklahoma StateUniversityThe energy distribution among the modes in an overmoded reverberationchamber operating at a particular frequency is studied forvarying tuner speeds. The understanding of this spread is importantin quantifying upsets of equipment in the chamber. The spectralcharacterization of a time varying electromagnetic field is done usingthe averaged periodogram approach. The complex insertion loss S21is the measured quantity and an estimation of the power insertionloss that will be used in the determination of Q factor, is obtainedfrom the sampling data for varying angular positions of the tuner.The same procedure is followed for varying tuner speeds and the Q isreported. The autocovariance for this random process can be foundby taking a Fourier transform of the spectral density function. Theautocovariance function helps in determining the number of independentsamples of the field. The field experienced by an EUT in theusable volume due to a continuous rotation of the tuner is analyzed.Evaluation of Test Reproducibility of Calibration inReverberation ChamberJinliang He; Rong Zeng; Shuiming Chen; and Bo Zhang, —Electromagnetic Environment Research Group; Fan Wu, High Frequency &Microwave Division; and Zhiyong Yuan, Electromagnetic EnvironmentResearch GroupThe position of the transmit antenna is analyzed and evaluated accordingto the measurement data in our developed reverberation chamber.The calibration parameters of the reverberation chamber are also evaluatedfor different working volumes. The key parameters such as theaverage normalized electric field and the receive antenna calibrationfactor are analyzed in detail. It is indicated that the definition of theworking volume and the different position of the transmit antenna hasa little influence on the test reproducibility of calibrations.REVERBERATION CHAMBER MEASUREMENTS IIAn Investigation of the Shielding Performance of PCB-levelEnclosures using a Reverberation ChamberYuhui He; and Andrew Marvin, — University of YorkPCB-level shielding enclosures differ from the other shielding productsin several aspects due to their small volume and therefore posenew challenges to the evaluation of performance. This paperdescribes several possible approaches and issues about using a reverberationchamber to accomplish a fast and reliable measurement.The interaction between the internal source and the enclosure is alsoinvestigated. In addition, the performance of the enclosure in isolatingnear-field interference in a high-Q environment, which is generalin practical applications, is compared with the measurement resultfrom the proposed reverberation chamber method. An approach isalso introduced to indicate the impact of changing environment tothe near-field coupling.In-situ High Field Strength Testing Using a TransportableReverberation ChamberFrank Leferink, Thales NederlandA reverberation chamber can create a very high field strength withmoderate input power. Existing chambers are making use of a paddlewheel to change the resonant modes in the chamber. In the caseof a stepper motor, the field is stable for some time, and this type ofreverberation chamber is called a mode tuned reverberation chamber.If the paddle wheel is continuously rotating we call it a mode stirredreverberation chamber. The mode stirred is much faster in measuringthan the mode tuned, but for some applications where theequipment under test has a long dwell time the mode tuned is preferred.A transportable reverberation chamber with varying anglesbetween wall, floor and ceiling and with vibrating walls has beenused for in-situ testing of a large radar antenna system. Inside thisVibrating Intrinsic Reverberation Chamber (VIRC) a diffuse, statisticallyuniform, electromagnetic field is created without the use of amechanical, rotating, mode stirrer. This chamber results in a betterhomogeneity and increased field strength compared to conventionalmode stirred reverberation chambers. But the VIRC has a disadvantagebecause it cannot be used for mode tuning. In this paper, aTuneable Intrinsic Reverberation Chamber (TIRC) is presented. Thechamber is still made of flexible material and thus transportable, butthe modes are changed using either a paddle wheel or by moving thewalls in small incremental stepsComparison of Different Definitions of Field Strength Usedin Reverberation Chamber StandardsLuk Arnaut, National Physical Laboratory; Hans Georg Krauthaueser,Otto-von-Guericke-Universitaet Magdeburg; and Magnus Hoeijer, FOISwedish Defence Research AgencyIn different standards involving reverberation chambers, the fieldstrength is defined either using the vector magnitude (total) electricfield, or the magnitude of a Cartesian (rectilinear) component. Wecompare these methods for determining the maximum field strength.The ratio of the maximum of the total field to the maximum of aCartesian component is a random variable whose probability distributionand statistics are derived and investigated. The mean value of thisratio is compared with the ratio of the respective mean values. Its standarddeviation enables the estimation of confidence levels when comparingor converting between single measurements of the maximumtotal and maximum rectangular field. Theoretical results are comparedwith measured results obtained in different reverberation chambers.How to Avoid Unstirred High Frequency Components inMode Stirred Reverberation ChambersOlof Lunden, FOI; and Mats Bäckström, Saab CommunicationsA goodness of fit test of the assumed Chi- Squared distribution, ofthe power received by an antenna in a reverberation chamber, is a very©<strong>2007</strong> IEEE www.emc<strong>2007</strong>.org