A simple method for calculating electric and magnetic fields inGTEM cell

A method based on coordinate transformation is presented to calculate the electric and magnetic field distributions in gigahertz TEM cells (GTEM cells). Here quasi-static approximations are employed, therefore the results are valid once operational frequencies well below the cutoff frequency of the cell. The method is illustrated by calculating the fields in a typical test structure. The results indicated here are useful in radiated emission and susceptibility studies     

A Complete Model for Simulating Magnitude and Phase of Emissions from a DUT Placed Inside a GTEM Cell

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.     

A treatment of the phase properties of GTEM to open-area test-sitecorrelation techniques

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     

An Advanced Correlation Algorithm between GTEM and OATS for Radiated Emission Tests

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.     

GTEM室与开阔场的辐射测量之间关系研究

该文详细推导了用电、磁偶极矩展开表示的电小尺寸辐射体在 GTEM室的辐射功率与开阔场中辐射场之间的理论关系,修正了 Lee理论中相应公式,并将理论结果与标准单极子辐射源实验结果进行了比较。结果表明两者符合的很好。这说明 GTEM室和开阔场辐射测量具有密切的相关性。对于电小尺寸的辐射体,GTEM室不仅可以用于 EMS测试,也可用于做 EMI测试。     

吉赫横电磁波传输室传输特性的宽频带分析

吉赫横电磁波传输室(GTEMcell)上限工作频率可达几个吉赫,因而在电磁兼容测量中得到越来越广泛的重视和应用。本文在非正交坐标系下采用FDTD(时域有限差分)法求解电磁波在GTEMcell中的传输特性,给出了GTEMcell中TEM模的横向分布和纵向分布,分析了高阶模对场分布均匀性的影响,由此确定了GTEMcell的上限工作频率范围。计算及分析结果对GTEMcell的设计和使用具有重要意义。     

On correlating TEM cell and OATS emission measurements

The use of single-port broad-band TEM cells for both near-field and far-field radiated emission testing is considered. The approach is to model the radiation from the device under test (DUT) as due to an equivalent set of multipoles. Assuming the DUT is electrically small only the initial multipole moments, the electric and magnetic dipole terms, need be retained. A sequence of TEM cell measurements is then used to determine the equivalent DUT dipole moments, The dipole model then allows one to simulate DUT emissions both in free space and over a ground screen. Thus, emission measurements over an open area test site (OATS) as called for by various standards may be simulated. Such measurement schemes have previously been successfully developed for standard two port TEM cells. However, certain broad-band TEM cells are single-port devices; thus, some modification of the previous approach is required. This paper reviews the basics of the multipole model as it relates to TEM cells, details various measurement schemes appropriate to single-port TEM cells, and presents examples of measured emission data, both near field and far field, in all cases considered, the correlation between emission data measured directly over a ground screen and simulated ground screen data based on TEM cell measurements is excellent     

A Method to Minimize Emission Measurement Uncertainty of Electrically Large EUTs in GTEM Cells and FARs Above 1 GHz

This paper presents an emission measurement technique with reduced uncertainties for electrically large equipment under test (EUTs) in gigahertz transverse electromagnetic (GTEM) cells and fully anechoic rooms (FARs) above 1 GHz. A small and a large EUT were measured and the results obtained in the GTEM cell were validated against those obtained in a FAR. Measurements in a FAR were made, for the small EUT, in the conventional way with an azimuth scan and, for the large EUT, with a limited antenna height scan. Key findings are that similar scanning is required in the GTEM cell and that the three-orthogonal-position (TOP) method of EN61000-4-20 is not appropriate for EUTs that have multilobed radiation patterns. In other words, GTEM cells and FARs are sensitive to directional properties of EUTs, and both methods require further scanning for electrically large EUTs     

On determining the maximum emissions from electrically largesources

This paper examines the use of measurements of the total radiated power from an arbitrary source, combined with theory-based estimates of directivity or quality factor, to accurately predict the maximum electric field radiated by the source either at a line-of-sight distance or in a resonant volume. The approach using total radiated power avoids source rotations during testing and is an efficient alternative to current emission test methods. Examples of simulated (random source set) and measured (box with holes) planar-cut radiation-patterns for electrically large sources are presented. Both simulated and measured data agree well with theoretical estimates     

GTEM cell facility use during project development phases for automotive

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.     

Modeling and Measurement of Radiated Field Emission From a Power/Ground Plane Cavity Edge Excited by a Through-Hole Signal Via Based on a Balanced TLM and Via Coupling Model

A balanced transmission line model (TLM) and via coupling model is proposed for efficient simulation of radiated field emission from a power/ground plane cavity edge, where the radiated field emission is excited by a through-hole signal via in a multilayer package and printed circuit board (PCB). The radiated field emission is simulated and measured with a series of test boards. The simulation agrees fairly well with the measurement confirming the preciseness and usefulness of the proposed model. It is shown that the through-hole signal via is a considerable source of the radiated field emission as well as the signal loss. When the signal trace is switching vertically stacked reference planes, the signal return current path is disconnected at the via and the impedance becomes extremely high. A significant amount of insertion loss and radiated field emission is generated at resonance frequencies of the plane cavity. The effect of a decoupling capacitor fence (De-Cap Fence) at the edge of the board to mitigate the radiated field emission is examined. The proposed model confirms that the De-Cap Fence changes the resonance mode and frequency of the plane cavity, and reduces the radiated field emission     

Assessment of digital integrated circuit electromagnetic emissionbased on radiated power evaluation

This paper deals with the assessment of digital integrated circuit (IC) electromagnetic emission (EME), and concentrates on the specific aspect of EME of long external wiring, driven by IC input-output pins. In particular, the contribution of single IC pins is investigated by analyzing the structure composed of an IC output driver connected via a microstrip line to a receiver. A transmission-line model is used, and an approach based on the concept of radiated power is applied to the characterization of single-pin IC EME in terms of external-wiring radiation effects. By the analysis of typical driver-wiring configurations, it is shown that the spectrum of the driver output current is the quantity of interest, and that the use of wiring with smaller characteristic impedance leads to larger radiated power. The use of a specific test setup (IEC 61967-4-150-Ω direct coupling method) for the experimental assessment of single pin IC emissions is also considered. Frequency-dependent setup effects are experimentally ascertained via a scattering parameter characterization, and definition of suitable circuit functions. An estimate of the degree of correlation between voltage measurements foreseen by the test procedure and the total power radiated by the loading network of an IC driver is derived     

用GTEM室做EMI测试的电小尺寸概念

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。     

Calculable field generation using TEM cells applied to thecalibration of a novel E-field probe

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     

Applications of the Near-Field Techniques in EMC Investigations

A completely automatic near-field mapping system has been developed within the Research Institute for Electronic Embedded Systems (IRSEEM) in order to determine the electromagnetic field created by electronic systems and components. This test bench uses a 3-D positioning system of the probe to make accurate measurements. This paper presents some applications of the near-field techniques in EMC investigations. In the first part, near-field measurements are used to locate precisely the electromagnetic sources of a limiter device. In the second part, we present an equivalent model of the radiated emission of an integrated circuit. In the last part, the near-field test bench is used to characterize faults in a cable.     

开关型电源适配器辐射骚扰对策

本文结合某种电源适配器辐射骚扰的试验情况,针对试验过程中出现的问题简单介绍了开关电路引起的辐射骚扰的改进思路及整改情况.     

TEM waveguides for EMC measurements

An overview of TEM waveguide electromagnetic compatibility (EMC) test facilities applicable to radiated emission and immunity measurements is given. Measurements of the field homogeneity in two TEM waveguides of different style are discussed. A statistical weighting of the measured electrical field is used to compare the results with standards requirements     

Field measurements made in an enclosure

This paper presents a survey of radiated emission and susceptibility measurement methods which can be employed to evaluate the electromagnetic interference (EMI) characteristics of electronic systems. The paper reviews conventional anechoic-chamber and shieldedenclosure-measurement methods, as well as alternate methods which have been developed to circumvent measurement problems associated with radiated measurements in conventional shielded enclosures. Alternative methods presented include hooded antennas, mode perturbation, statistical sampling transverse electromagnetic (TEM) cells, and other techniques such as parallel-plates low-Q-enclosures, and long-wire-antennas. A qualitative comparison of each technique in terms of advantages and limitations is also given.     

解析401～402MHz与405～406MHz短距离设备电磁兼容欧洲标准

介绍了短距离设备欧洲标准ETSI EN 302 537-1 V1.1.2的测试条件、电源要求和环境要求,分析了辐射测试场地和测试布置。最后,详尽解读了401～402 MHz与405～406 MHz频段超低功耗医学设备的频率误差、发射带宽、有效辐射功率、杂散发射、低电压条件下的频率稳定度、基于低功率低占空比条件的频谱访问等发射机参数要求,以及接收机杂散的要求。     

GTEM室与开阔场的辐射发射相关研究

给出了用Wilson和lee的方法推导并经过订正的GTEM室端口输出推算辐射体在开阔场中辐射场的公式，指出了使用条件，介绍了用该方法进行了18个频点实验的结果，并对这两种方法进行了对比。结果表明用GTEM室做EMI测试是有希望的，但还需要进一步深入的理论和实际去研究。