镜像对称结构对多馈源混响室场性能的影响

为解决混响室大体积与场性能高要求之间的矛盾,提出了一种基于镜像原理的多馈源混响室的设计思想,从原理上分析了镜像多馈源混响室的可行性和有效性,并通过仿真计算研究了镜像双馈源混响室的场性能.结果表明,在输入功率一定时,两个单混响室系统组合成镜像双馈源混响室后,在工作区域的场均匀性能不下降的基础上,不但可用于电磁兼容测试的工作区域体积大幅度增大,而且测试区域的电场强度也得到了提高.同时,对镜像多馈源混响室进行了进一步的扩展分析,得出了组成镜像多馈源混响室的单混响室系统数量的理论表达式.     

A closer look at reverberation Chambers - 3-D Simulation and experimental verification

This paper presents three-dimensional (3-D) full-wave simulations of the electromagnetic field inside a medium-sized reverberation chamber. A frequency-domain method-of-moments approach based on the electric field integral equation is used. A synopsis of the computational challenges particular for reverberation chambers is described and a detailed overview on the chamber modeling procedure is given. The electric field inside the chamber is computed and the influence of small geometric details and asymmetries is investigated as well as the effect of different excitations and stirrers. It is demonstrated that a statistics-based validation of reverberation chamber simulations is insufficient. To validate simulation results, therefore extensive near-field measurements inside the prototype reverberation chamber are performed. The complete 3-D reverberation chamber simulation, considering stirrers, door, and various practical excitations, accurately predicts the fields within the chamber in the important lower-to-medium frequency range and thus represents a reliable tool facilitating reverberation chamber optimization.     

Requirements for an effective reverberation chamber: unloaded or loaded

In this paper, we present two versions of a threshold metric for the purpose of accessing the effectiveness of a reverberation chamber. One metric is based on the chamber quality factor (Q), and the other is based on the volume of the loaded reverberation chamber. These metrics are baseline quantities that must be exceeded in order to have an effective reverberation chamber. These threshold metrics are obtained from two different approaches. The first approach is based on a free-space transmission formulation and the scalar mean power density associated with the "stirred energy" in the chamber and requires that the stirred energy exceeds the unstirred energy throughout most of the chamber volume. The second approach is obtained by requiring that the amplitude of the electric (or magnetic) field satisfies the expected Rayleigh probability density function throughout most of the chamber volume. We present an application of these metrics for the case of a reverberation chamber loaded with spheres composed of lossy materials.     

双发射天线对混响室场性能影响的数值分析

提出了双天线激励混响室的方法,研究了双天线激励对混响室场性能的影响。分析了双天线改善混响室场均匀性的原理,对单天线激励下的混响室模型以及处于不同位置的双天线激励下的混响室模型进行了仿真计算,从场均匀性和场强两个方面研究了双天线对混响室场性能的影响,对双天线影响场强的机理进行了分析。研究表明:采用双天线激励改善了混响室工作区域的场均匀性;采用双天线可以降低对功率放大器的要求,降低大型混响室测试成本。最后对双发射天线在大型混响室中的应用进行了探讨和展望。     

EMC混响室电磁场模态研究

混响室谐振腔激励的三维电磁场的推导一般采用并矢格林函数的方法,物理意义不太明显。用本征函数迭加的方法推导混响室有源激励的电磁场分布公式,有利于正确建立混响室电磁结构模型,树立正确的物理概念。并根据公式及其推导过程,分析了混响室EMC电磁工作机理,以此将EMC混响室电磁工作状态按模式状况进行了系统地分类,为混响享研究设计提供理论指导。     

混响室设计与校准测试

给出了混响室测试系统的设计方法和基本性能的预测分析.根据设计建造了混响室,并且采用自动化测试软件完成了校准测试,分析了电场均匀性、品质因数等性能指标.测试表明建造的混响室性能完全符合测试标准的规定,多次测量重复性很好.最低可用频率200 MHz,电场均匀性小于3 dB.可以用来进行电磁兼容辐射发射和辐射抗扰度测试.     

搅拌器配置对混波室场影响的FDTD分析

混波室能提供统计均匀和各向同性的场,是一种用于辐射发射、屏蔽效能及敏感度测试等电磁兼容测试的小室。本文用FDTD方法分析混波室的场分布,分析了搅拌器不同大小及不同倾斜角度对混波室时间平均场分布的影响,为实际设计混波室的搅拌器提供参考。最后给出了与数值分析相一致的实验结果。     

Efficiency measurement of UWB antennas using time reversal in reverberation chambers

Using the reverberation chamber to obtain antenna radiation efficiency is considered. The reverberation chamber, which has for many years been used for electromagnetic compatibility measurements, can also be used with great advantage for antenna measurements since it simulates effectively a uniform multipath propagation environment. How a reverberation chamber can be used to measure the ultra-wideband (UWB) antenna efficiency in a very short time is described. The procedure based on time domain is described and some experimental results are given and compared to measurements obtained by the Wheeler cap method extended by Schantz to UWB antennas.     

Shielding effectiveness measurements of materials using nested reverberation chambers

The use of reverberation chambers for determining the shielding effectiveness has the advantage over other techniques in that the reverberation chamber exposes the material to a more realistic environment. That is, in a reverberation chamber, the fields are incident on the material with various polarizations and angles of incidence. There are various reverberation chamber techniques found in the literature and international standards. These techniques can give incorrect results because aperture and cavity-size effects are not correctly accounted for. In fact, we show that for no sample in the aperture, these techniques give a nonzero result for shielding effectiveness. In this paper, we review existing techniques and present a new technique for determining the shielding effectiveness of materials from nested reverberation-chamber measurements. The new approach accounts for aperture, cavity size, and chamber loading effects. Various examples are presented to illustrate the utility of the new approach, and a discussion on edge treatments of the materials is given.     

混响室校准与辐射抗扰度测试

在对混响室的基本原理进行简要介绍的基础上,依据标准IEC61000-4-21中的规定,对混响室的校准方法及操作过程进行了详细介绍和分析,并对在混响室内进行辐射抗扰度测试的方法及步骤进行了介绍。     

FDTD analysis of plane wave superposition to simulate susceptibility tests in reverberation chambers

The behavior of a device in a reverberation chamber can be analyzed as the same device irradiated by random plane waves. This work proposes an application of the finite difference time domain method to analyze the device by using a superposition of random plane waves, simulating the behavior of a reverberation chamber. The analysis of a transmission line compared with theoretical and experimental results in a reverberation chamber is reported.     

Use of Reverberation Chambers to Determine the Shielding Effectiveness of Physically Small, Electrically Large Enclosures and Cavities

With the proliferation of small electric devices in recent years, along with various other applications, there is a growing need to test and determine the shielding properties or shielding effectiveness (SE) of physically small (but electrically large) enclosures or cavities. In this paper, we discuss how a reverberation chamber technique can be used to measure the SE of such enclosures. The approach consists of placing the small enclosure inside a reverberation chamber and using frequency stirring to excite the reverberation chamber. A small surface probe (i.e., a monopole) is mounted on the inside wall of the small enclosure to measure the power level inside the small enclosure. We present measured data from various other reverberation chamber approaches obtained from various enclosure configurations. The data from these other reverberation chamber approaches are used to validate the proposed approach. We also compared measured data to theoretical calculations of the SE for two small enclosures with circular apertures. These various comparisons illustrate that the proposed technique is a valid approach for determining the SE of physically small (i.e., cubic enclosure dimensions of the order of 0.1 m and smaller), but electrically large enclosures (that support several modes at the lowest frequency of interest).      

搅拌器配置对混波室独立采样点的影响

分别用数值计算(FDTD)和实验方法给出了不同频率不同搅拌器配置情况下混波室功率密度的相关函数,并计算了相应的独立采样数,数值计算结果与实验结果吻合,表明了算法的有效性.所得结论为混波室搅拌器的设计提供了依据.     

Boundary fields in reverberation chambers

A previous plane-wave integral representation for fields in a reverberation chamber is extended to analyze fields near the boundaries of a rectangular chamber. The field point can be located near a single wall, a right-angle bend, or a right-angle corner. Multiple image theory is used to ensure exact boundary conditions. Expressions for the ensemble average of the squares of the electric and magnetic field components illustrate the evolution of the fields from the chamber boundary to the center of the chamber where the fields are statistically uniform. The results are relevant to the useful test volume of rectangular reverberation chambers or, equivalently, how far test objects must be located from chamber walls to obtain a uniform test field.     

A two-dimensional finite-element analysis of reverberation chambers

A two-dimensional (2-D) analysis of reverberation chambers is performed at cutoff. The structure considered is lossless and corresponds to an infinite quality factor (Q) chamber. The concept of frequency stirring is used to generate field data for a discrete set of modes and the resulting statistics are analyzed. The field statistics are examined for TE and TM modes. This analysis yields statistics similar to the expected reverberation chamber statistics for the fields. Mechanical stirring is also examined and a connection to the peak-frequency deviation is presented     

混响室校准及测试

本文首先对混响室的发展、原理、主要性能参数进行了介绍,在此基础上依据标准IEC 61000-4-21中的规定,对混响室的校准方式进行了详细介绍和分析,并以辐射电磁场抗扰度为例,具体说明在混响室内进行测试的方法步骤.     

Validation of a Three-Dimensional Transmission Line Matrix (TLM) Model Implementation of a Mode-Stirred Reverberation Chamber

Reverberation chambers are attractive electromagnetic compatibility test facilities, both economically and technically. Careful design and analysis of these facilities are important, if the results obtained are to be treated with a high level of confidence. Numerical modeling is an important part of the process of reverberation chamber design and analysis. Hence, it is important that the modeling techniques to be used are appropriately validated. Much of the published work to date takes either a statistical or a deterministic view of validation. This paper provides validation evidence for a low-resolution transmission line matrix (TLM) model of a reverberation chamber in a manner approximating the way in which the chamber is used, i.e., validating based on the effects of a simple device under test. A variety of statistical and heuristic approaches have been used to quantify the level of agreement, intending to set the likely lower bound for the quality of comparisons between simulations and measurements. While not drawing any "universal" conclusions about the veracity of the TLM technique, the paper concludes that a relatively simple model of a reverberation chamber provides a useful analysis of the chamber with close comparisons between modeled and measured data.     

Shielding Measurements of Equipment Enclosures in the Radiating Near Field

To evaluate the shielding performance of an equipment-level enclosure, a new measure termed shielding power ratio is proposed, which includes the average shielding power ratio (AS) and a statistically based enhancement factor. Two measurement environments, the anechoic chamber and the reverberation chamber, are considered and compared. To achieve a quick estimate of such measure, the reverberation chamber is proposed to measure the AS. The enhancement factor can be derived from the statistical analysis on both measurement results and simulation results. Based on the enhancement factor and the total radiated power, the maximum power density radiated from the enclosure can be estimated accurately. The paper is informing new developments in IEEE Standard 299.     

Reverberation Chamber技术应用于手机OTA量测

一般混响室多用于EMC测试中,文章针对手机的OTA全辐射功率与全性灵敏度在混响室中测试方法提出说明,并针对小型的多输入多输出天线于多重路径环境测试测试方式说明。     

Comparison Between Different Criteria for Evaluating Reverberation Chamber Functioning Using a 3-D FDTD Algorithm

This paper is devoted to the comparison between different criteria used to evaluate the functioning of a mechanically stirred reverberation chamber. Usual criteria based on power or electric fields are considered, and we also propose a criterion based on the Kolmogorov-Smirnov test, called in this paper ldquosuccess ratio to Kolmogorov-Smirnov testrdquo (SRKS). The SRKS represents the acceptation ratio of this test applied at several points of the working volume, when considering a field component and its associated theoretical distribution. After a presentation of the criteria and of the studied chamber, data issued from 3-D finite-difference time-domain simulations and measurements are used to analyze the chamber functioning by the use of these criteria. This study is performed on a large frequency band, in the lossless case as well as with a lossy chamber, and for several stirrer shapes, to emphasize the influence of these parameters. The comparison of the usual criteria with the SRKS shows the SKRS is an accurate test to estimate the lowest usable frequency of a given reverberation chamber.