Journal ArticleDOI
Measurements of unintentional electromagnetic emissions
M.T. Ma,G.H. Koepke +1 more
- Vol. 74, Iss: 1, pp 110-111
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TLDR
In this paper, a new method for determining the radiation characteristics of leakage from electronic equipment or other unintentional radiators of interference is presented, and the theoretical background and specific measurement procedures for the method using a transverse electromagnetic cell are outlined.Abstract:
A summary of a new method for determining the radiation characteristics of leakage from electronic equipment or other unintentional radiators of interference is presented. The theoretical background and specific measurement procedures for the method using a transverse electromagnetic cell are outlined. The theory and measurements have been verified in referenced work by the results of a simulated theoretical example and an experiment using a spherical dipole radiator. Mathematical analysis of the uncertainties in the final, extracted results when the experimental data are degraded by the background noise and measurement imperfections is also available.read more
References
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Journal ArticleDOI
Generation of Standard EM Fields Using TEM Transmission Cells
TL;DR: In this article, a new technique developed at the National Bureau of Standards (NBS) for establishing standard, uniform, electromagnetic (EM) fields in a shielded environment is described.
Journal ArticleDOI
Emission Characteristics of Electrically Small Radiating Sources from Tests Inside a TEM Cell
TL;DR: In this article, a method of determining the individual dipole moments and the cross-components of such a dipole system, by tests inside a transverse electromagnetic (TEM) cell, is presented along with some experimental results.
Proceedings ArticleDOI
A New Method for Determining the Emission Characteristics of an Unknown Interference Source
G. H. Koepke,M. T. Ma +1 more
TL;DR: In this article, the authors describe a method to determine quantitatively the characteristics of unintentional EH emitters, where an unknown source object is placed at the center of a transverse electromagnetic (TEM) cell and its radiated energy couples into the fundamental waveguide mode.
Proceedings ArticleDOI
Predicting Free-Space Radiated Emissions from Electronic Equipment Using Tem Cell and Open-Field Site Measurements
M. L. Crawford,J. L. Workman +1 more
Abstract: This paper gives an analysis for determining equivalent free-space (reference environment) radiated emissions from electronic equipment using transverse electromagnetic (TEM) cells and openfield site measurements. Test results and an estimate of the accuracy of emission measurements made using a "control standard emitter" in TEM cells and on an open-field site are given and compared with the standard emitter's theoretically predicted free-space emissions. 1.0 INTRODUCTION To perform meaningful radiated emission measurements, basic assumptions or characteristics which influence the measurement results must be carefully defined. For example: (a) That which constitutes the equipment under test (EUT) must be defined; (i.e., what is the aperture of the EUT, does it include input/output and power line leads, peripheral equipment? etc.) Such definition influences ones ability to define a consistent aperture and hence the repeatability and accuracy of the measurement results. (b) EUT operational conditions must be carefully simulated to match real-world conditions or, at least, to allow for correlation of results with some reference. This includes proper termination of input/output leads, the simulation of an operational environment and layout, the simulation of proximity effects, polarization effects, etc., and their careful documentation to assure repeatability. (c) Interaction effects between the EUT and its environment must be carefully controlled/determined and noted. This is especially true when measurements are to be performed inside shielded enclosures and/or in near-field conditions. (d) How the EUT is accessed for operational and monitoring purposes is also critical in influencing the measurement results. Factors such as these suggest classifying EUTs into three categories: (1) Control Standard EUT This EUT must be character!zable analytically, is self-contained (no external elements) and has a stable, predictable, repeatable output. The spherical dipole radiator used for obtaining the data given in this paper is an example of this type of EUT [1]. (2) Self-Contained EUT This EUT has no external connections but may not be characterizable analytically in the simple sense of the control standard. An example of this EUT would be a portable receiver or internal battery-operated device that requires no input/output or power line leads, (3) Dependent EUT This general class of EUTs requires input/output from or to other equipment and/or requires external power to operate. The radiated emissions from such an EUT are influenced by numerous factors including those indicated above. Obviously, obtaining repeatable, meaningful results of radiated emissions becomes progressively harder for successively more complex categories of EUTs. The intent of the work described in this paper was to compare radiated emission measurement results obtained using transverse electromagnetic (TEM) cells with openfield site measurements (i.e., measurement techniques), hence, a category (1) EUT was selected. The control standard EUT is a small, 10 cm diameter, self-contained, spherical dipole that radiates a well defined, stable field in free space [1]. A photograph of the dipole assembly is shown in figure 1. U.S. Government work not protected by U.S. copyright. 80 The field radiated from this dipole can be .calculated based on its physical parameters and a measurement of the voltage across its gap [2]. The dipole can then be placed in a TEM cell or other enclosure and on an open-field site and its radiated emissions measured for comparison with the theoretically predicted emissions. Emission measurements made using EUT categories (2) and (3) would be much more difficult since the results are EUT dependent; thus, such measurements/evaluations were considered beyond the scope of this paper. However, the results obtained for the "control standard EUT," category (1), can be applied to the more general categories and give insight into the feasibility and/or desirability of using a TEM cell for radiated emission measurements. TEM cells are a relatively new tool for measuring the radiated emissions from electronic equipment [3]. Figure 2 shows a cut away view of a TEM cell being used for general testing (category (3)). Category (1) is greatly simplified since the EUT has no.external power or input/output lead requirements. One of the great advantages of using a TEM cell to perform emission measurements is the potential for correlation of the results to openfield measurements. This paper gives an analysis for obtaining such a correlation by determining the equivalent free-space (reference environment) radiated emissions from an EUT using TEM cells and a ground-screen open-field site. Test results and an estimate of the accuracy of the emisssions measurements made using a "control standard emitter" in TEM cells and on an open-field site are also given. These are then compared with the control standard emitter's theoretically predicted free-space emissions. 2.0 PREDICTING FREE-SPACE EQUIVALENT RADIATED EMISSIONS FROM ELECTRONIC EQUIPMENT USING TEM CELL MEASUREMENTS v 2 m \ ,/m R = tfZ K ( I ) x E cos e VT *