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。     

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。     

一种有前景的辐射EMI测试方法--用GTEM小室做EMI测试

文中简介了用GTEM小室做电磁兼容辐射EMI测试的方法，概念，现状和实际测试结果，通过对电偶极源，磁偶极源和一个实际雷达分机在GTEM室和开阔场的实际测试，证实了用GTEM室做辐射EMI预测试或预测试的可行性。     

GTEM室性能测量系统研制

吉赫兹横电磁波室(GTEM室)是电磁兼容领域重要的测试场地。为解决GTEM室性能测量问题,从GTEM室场均匀性、TEM模的测量原理入手,中国计量科学研究院研制了GTEM室性能测量系统及配套软件。经实验验证,系统完全符合IEC 61000-4-20:2022要求,可以实现GTEM室内各测量位置点处的三维电场分量、GTEM室净馈入功率等参数的自动测量以及场均匀性、TEM模的自动计算。GTEM室性能测量系统工作稳定,原始数据采集及处理准确可信。目前中国计量科学研究院已具备依据IEC 61000-4-20:2022对外开展GTEM室性能测量服务的能力。     

大型吉赫横电磁波室的数值分析

为了解10m以上的大型GTEM（吉赫横电磁波）室的传输特性和场的均匀性,利用FDTD（时域有限差分）法对大型GTEM室进行了数值分析。选用了上升前沿为纳秒级的高空电磁脉冲波形和高频特性较好的高斯脉冲源作为激励源,计算结果表明对于10m长的GTEM室可以无失真地传输1．5GHz的电磁波,所以能够利用GTEM室传输上升前沿为纳秒级的快上升沿电磁脉冲。“三分之一”测试区域的场强不均匀性小于±2dB,可以用做精度较高的测量区域。     

强电磁脉冲环境的模拟

基于一套由脉冲电压发生器和GTEM室组成的模拟装置,对LEMP和NEMP进行了模拟.分别对这两种强电磁脉冲进行了采集,结果表明通过调整模拟装置的参数,该装置既可以模拟LEMP环境,又可以模拟NEMP环境,在GTEM室内一定区域能产生相对均匀的电磁脉冲场环境,可用于敏感器件的电磁敏感度实验.     

追求天线校准场地性能的10米法电波暗室

用于各种电器、电子产品辐射骚扰试验的天线,通常在是开阔场进行校准的。这种用来校准天线的开阔场被称为CALTS(Calibration Test Site),包含测试中的不确定度在内,与理论计算值偏差要求在     

GTEM小室性能测试方法

文章在GTEM小室原理及其应用的基础上详细介绍了GTEM小室的性能指标,并结合具体测试给出了GTEM小室性能测试方法。结果表明,本测试方法所使用的时域阻抗、电压驻波比、场均匀性及屏蔽效能这四个指标能够较好地反映GTEM小室的技术性能。     

电磁发射GTEM室测量方法

应用吉赫横电波(GTEM)室条件对RE102、CE102项目实现测试,测试结果达到相对准确的诊断测试使用要求,可作为低成本EMC诊断测试方法和装置的范例,适用于箱体级设备及分系统的诊断测试。     

2021 IEEE EMC&SIPI and EMC Europe国际学术研讨会--提名文章(一)

Statistical Approach to Verification of Field Uniformity and Dominance of the Primary Field Component in the GTEM Cell摘要:根据IEC 61000-4-20:2020要求,开发了能够在GTEM室中的任意关注点设置电场强度的软件,用于在一组点中设置均匀场区,并验证主场分量相对于次场分量的优势。软件采用Microsoft.NET编程平台,用统计学标准检验均匀性。IEC 61000-4-20:2020中要求75%的置信水平,适用于N=5的总点数,75%意味着4个点;但当N=6时,该置信水平在某些情况下会给出错误的结论。作者提出了其他合适的置信水平。应用EMCO公司的GTEM 5317室验证了该软件。     

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.     

Extrapolating near-field emissions of low-frequency loop transmitters

This paper investigates the emission of fields and field attenuation rates from electrically small transmitting loop antennas in the presence of a general half-space. Considerations are made for the practical effects of antenna loop dimension and source-to-sensor impedance coupling. The resulting field attenuation rates correlate well with open area test site (OATS) measurements. The tables provided may be readily used to extrapolate measured low-frequency emissions to common regulatory limit locations.     

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 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     

IMPROVEMENT OF EXPRESSION FOR EXCITATION BY AN ELECTRIC DIPOLE IN GTEM CELL

On the basis of Wilson‘s work in which the vertical electric dipole is centrally located in GHz Transverse ElectroMagntic(GTEM) cell, we deduce the expression for the field distribution excited by an electric dipole in the case that the dipole is not centrally located.It will be useful for EMCmeasurements using GTEM cell.     

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.     

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