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The gigahertz transverse electromagnetic (GTEM) cell is a very attractive environment for the measurement of radiated emissions from electrically small equipment under test (EUTs). However, the GTEM is only accepted by the relevant measurement standards as long as the measurements in a GTEM can be used to predict the field that a particular EUT would produce on an open-area test site (OATS). Techniques for predicting equivalent OATS radiated fields from measurements in a GTEM have been developed. The techniques include the assumption that the dipole moments, which represent the radiation of an EUT, are all in phase. We analyze the case where the EUT dipole moments are not in phase and propose a new upper limit for the predicted OATS radiated field. Our new limit is up to 5 dB greater than the maximum predicted by the existing techniques, but over most of the frequency range the difference with the existing technique is about 3 dB 相似文献
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用GTEM室做EMI测试的电小尺寸概念 总被引:2,自引:1,他引:1
目前用GTEM室做辐射EMI测试的方法仅适用于电小尺寸辐射体,如何正确理解这个电小尺寸的概念是实用中很重要的问题,文章通过数学推导进一步明确了这个条件。 相似文献
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In all applications of the gigahertz transverse electromagnetic (GTEM) cell, there is an interplay between the equipment under test (EUT) and the cell reflecting metal walls, as represented by images of the EUT. Moreover, owing to the multiple reflections within the cell and to its tapering structure, the phenomenon of illumination and reillumination of the EUT can hardly be avoided. These problems, known as reactive effects of the cell, are investigated in this paper. A simple new approach for an efficient investigation of the interactions between the EUT and the cell is provided. Closed-form expressions for the reflection coefficient, the relative deviation in field, and the relative error in the induced current caused by the reactive effect of the cell are derived. Each of these expressions encompasses both the mutual influence of the EUT's radar cross section (RCS) and the reactive effects of the cell. It is shown that depending on the frequency-dependent phase factor ejpsi, strong and weak test conditions may occur since the overall incident field will exhibit maxima and minima. Hence, evidence showing that the total incident field impinging on the EUT generally deviates from the primary excited TEM field is provided. Moreover, the relative deviation in the field and the relative error in the induced current are quantified. Finally, the frequency dependence of the well-known one-third-rule of thumb is demonstrated. 相似文献
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A Complete Model for Simulating Magnitude and Phase of Emissions from a DUT Placed Inside a GTEM Cell 总被引:1,自引:0,他引:1
Ngu X.T.I. Nothofer A. Thomas D.W.P. Christopoulos C. 《Electromagnetic Compatibility, IEEE Transactions on》2007,49(2):285-293
Since the publication of IEC 61000-4-20, the gigahertz transverse electromagnetic (GTEM) cell has gained popularity in radiated emission and immunity electromagnetic compatibility tests. Various numerical methods such as finite-difference time-domain, finite element method, and method of moments have been used to model the GTEM cell in the pursuit of getting to know the characteristic of the GTEM cell with varying degrees of verification. In this paper, the time-domain transmission line model will be used to model the GTEM cell. The advantages of this method include high accuracy and the ability to model different materials. Thus, the GTEM is realistically modeled including radio absorbing material (RAM) and lumped terminations. In addition, the model of a realistic device under test (DUT) was also included in the GTEM model. The DUT consists of a standard sized box with an aperture, placed in different orientations inside the GTEM for power and phase measurements. The particular features of this paper are: 1) the inclusion of a realistic numerical model of RAM, 2) the inclusion of a realistic DUT model, 3) systematic verification of the model against measurements, and 4) the method of phase measurement in a GTEM cell. Good agreement between the experimental results and simulations is obtained. 相似文献
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This paper examines the calculable generation of electromagnetic fields for calibration purposes using TEM cells. In order to enlarge the bandwidth the use of a circular coaxial calibration cell (C3 cell) is proposed. Based on generalized telegraphist's equations the field is calculated. Results are compared with other common TEM cells (Crawford (1974) cell, GTEM cell). For field measurements a new isotropic field probe is considered. The proposed probe uses only one electrically short dipole with a diode detector and enables the measurement of both the magnitude and the polarization direction of an electromagnetic field. The manufactured probe was calibrated utilizing the C3 cell 相似文献
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《Electromagnetic Compatibility, IEEE Transactions on》2008,50(4):794-801
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Olivier Maurice François de Daran Frédéric Lafon Rabha Oussedrat Imad Ben Yacoub 《Microelectronics Journal》2004,35(6):563-569
The purpose of this paper is to present the results obtained with a gigahertz transverse electromagnetic mode (GTEM) cell for each phase of the project development, which consists of measuring and quantifying the integrated circuit's emissions and immunity compliance with automotive standards. These standards are defined using half anechoic chambers (HAC). Studies have already been conducted to compare trans electromagnetic (TEM) cell and HAC, or far-field emissions, and the test results show a limited correlation between TEM cells and the free space field or HAC. In this paper, it is shown that the correlation between the measurements made in a GTEM cell and HAC can be good enough in allowing us to use the GTEM facility during the research and development (R&D) phase (considering the facts that the HAC facility is often quite overloaded and of a high cost), that knowledge of the electromagnetic compatibility behavior of the integrated circuit is important for predicting the whole system's results as well as how to use an integrated circuit electromagnetic model to make the prediction of emissions. 相似文献
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Multisensor data fusion for surface land-mine detection 总被引:2,自引:0,他引:2
Filippidis A. Jain L.C. Martin N. 《IEEE transactions on systems, man and cybernetics. Part C, Applications and reviews》2000,30(1):145-150
Receiver operating characteristic (ROC) curves have been used to examine a novel target recognition system using a number of knowledge-based techniques to automatically detect surface land mines that are present in 30 sets of thermal and multispectral images. A summary of the results, graphed at a probability of detection greater than or equal to 96%, shows the false-alarm rates (FARs) obtained using various combinations of fusing sensors and neural classifiers averaged over the 30 images. The results show that using two neural-network classifiers on the input textural and spectral characteristics of selected multispectral bands, we obtained FARs of approximately 3%. Using polarization-resolved images only, we obtained FARs of 1.15%. Fusing the best classifier output with the polarization-resolved images, we obtained FARs as low as 0.023%. This result has shown the large improvement gained in the sensor fusion. Also, an improvement is shown by comparing these results with those reported in an existing commercial system 相似文献
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The formula of input impedance of dipole antenna in Gigahertz Transverse ElectroMagnetic (GTEM) cell based on the dyadic Green's function is first obtained in this paper. The validation of the formula is verified by the results of theoretical derivation and simulation with well agreements. In comparison with the formula of input impedance in free space, the relationship between the change of input impedance with the length of antenna and the position of antenna in GTEM cell is obtained. In addition, some meaningful conclusions are presented, which not only can be referred by the further research of ElectroMagnetic Interference (EMI) measurements in GTEM cell, but also provide the theoretical basis for testing compensation and error analysis. 相似文献
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Ji Z Hagness SC Booske JH Mathur S Meltz ML 《IEEE transactions on bio-medical engineering》2006,53(5):780-789
Gigahertz transverse electromagnetic (GTEM) transmission cells have been previously used to experimentally study exposure of biological cells to ultra-wideband (UWB), monopolar, electromagnetic pulses. Using finite-difference time-domain (FDTD) simulations we examine the time-dependent electric field waveforms and energy dose spatial distributions within a finite volume of biological cell culture medium during these experiments. The simulations show that when one or more flasks containing cell culture media are placed inside the GTEM cell, the uniform fields of the empty GTEM cell are significantly perturbed. The fields inside the cell culture medium, representing the fields to which the biological cells are exposed, are no longer monopolar and are spatially highly nonuniform. These effects result from a combination of refraction and distortion of the incident wave, combined with excitation of resonant eigenmodes within the cell culture medium volume. The simulations show that these distortions of the incident waveform may be mitigated by supporting the sample on a high permittivity pedestal and modifying the incident waveform to more closely approximate a Gaussian pulse. Under all simulated conditions, the estimated maximum temperature rises are completely negligible, ensuring that any experimentally observed unusual cell function or histopathology can be associated with nonthermal effects. 相似文献
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该文提出了一种使用吉赫兹横电磁波传输(GTEM)小室进行被动式超高频射频识别(UHF RFID)标签Delta Radar Cross Section (RCS)测试的方法。通过理论分析RFID标签工作时的等效电路及其散射特性,推导出GTEM小室中和自由空间中UHF RFID标签Delta RCS测试的等效性。并通过GTEM小室和全电波暗室的对比实验,验证了使用GTEM小室进行UHF RFID标签Delta RCS测试的可行性及实用性。 相似文献
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Klingler M. Egot S. Ghys J.-P. Rioult J. 《Electromagnetic Compatibility, IEEE Transactions on》2002,44(2):364-372
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 相似文献
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提出近场辐射电磁干扰模态测试方法,设计近场模态检验测试系统,采用近场电磁场头对待测设备进行扫描式测量,获得待测设备的近场电磁场分布情况,并根据测得电磁场强度大小可分析得到待测设备的辐射EMI模态。实验结果表明,该方法可对电子电路的近场辐射EMI模态进行有效识别和检验,分别得到近场辐射共模噪声和差模噪声EMI模态,为辐射电磁干扰噪声的抑制提供有益参考。 相似文献
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A novel experimental procedure to measure the total radiated power of an equipment under test (EUT) placed in a reverberation chamber (RC) is presented. In contrast to the well-established method of the IEC 61000-4-21, this new procedure does not rely on information obtained during the empty chamber calibration or the calibration with the EUT in place. Thus, the method is simpler, faster, and may have a smaller uncertainty budget. 相似文献
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Ae-kyoung Lee 《ETRI Journal》1995,17(3):45-63
This paper proposes an algorithm to improve the correlation between giga-hertz transverse electromagnetic (GTEM) cell and open area test site (OATS). It is based on the dipole modeling process of an unknown source object in a GTEM cell and on the evaluation of the approximate far field equations correlated with measured GTEM powers at output port of the GTEM cell. In this algorithm, the relative phase differences between dipole moments play an important part in modeling the test object as a set of dipoles and offer stable calculation of emission values. The radiated emission test using this algorithm requires fifteen orientations of equipment under test, but the increased orientations as compared with the previous method have little effect on the time needed for testing. Radiation from a notebook computer has been tested for statistical analysis of the correlation between GTEM data and OATS data. The emission test results of the notebook computer show that the mean, the standard deviation, and the correlation coefficient are ?0.62, 1.99, and +0.85, respectively. These figures indicate that this algorithm provides improved accuracy in the measurement of electromagnetic emissions over the previous method. 相似文献