Effectiveness of absorbing materials on reducing electromagnetic emissions from cavities measured using a nested reverberation chamber approach

Washbourne, Logan J.; Rajamani, Vignesh; Bunting, Charles F.; West, James C.; Archambeault, Bruce; Connor, Samuel

doi:10.1109/isemc.2014.6899097

Cited by 4 publications

(15 citation statements)

References 4 publications

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“…This equation shows that both the total AACS of the contents and the total ATCS of the apertures directly determine the SE of the enclosure at high frequencies. We see that the SE of an empty enclosure, , is as much a measure of its wall losses as it is of the transmission through its apertures [3], [4]. Furthermore, considering the cases where the enclosure is either empty or populated we find [3], [10] (2) which shows that knowledge of is in itself insufficient for predicting the SE of a populated enclosure.…”

Section: A Rc Shielding Measurementmentioning

confidence: 92%

“…Here we recall how this is determined analytically and approximated numerically. If the ACS of an object under plane-wave illumination by transverse electric (TE) and transverse magnetic (TM) polarized waves from spherical polar direction are denoted by and respectively then the AACS for plane-waves arriving from all directions is [8] (4) where is the average silhouette area of the object, which for a convex object is equal to a quarter of its surface area, .…”

Section: B Determination Of Aacsmentioning

confidence: 99%

“…Comparing the target AACS to the appropriate AAE according to (4) suggested that a RAM coverage factor of about 30% is required. For low loss enclosures, full-wave simulations have shown that the statistics of the internal field are independent of the distribution of losses and depend only on the total AACS [19]; however, for higher losses the electromagnetic diffusion model suggests that the diffuse field becomes inhomogeneous and dependent on the loss distribution [20].…”

Section: B Ram Based Recomentioning

confidence: 99%

“…Some work on modeling the effect of an enclosure's content on its shielding characteristics has been reported, mostly considering frequencies up to a few gigahertz [1], [2]. More recent work has shown how even the losses in enclosure walls impact on shielding performance at high frequencies [3], [4]. Proposals have been made to improve the relevance of shielding effectiveness (SE) metrics by incorporating loading into the enclosure during shielding measurements [5], [6].…”

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confidence: 99%

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Representative Contents Design for Shielding Enclosure Qualification From 2 to 20 GHz

Flintoft

Bale

Marvin

et al. 2018

IEEE Trans. Electromagn. Compat.

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Abstract-The electromagnetic environment inside a shielding enclosure is affected by the absorption characteristics of the contents, which should therefore be represented in shielding measurements and simulations. At frequencies up to a few gigahertz, lossy dielectric materials have previously been used as surrogates for printed circuit boards in enclosure shielding assessment, both experimentally and in simulations. However, no systematic methodology for the design of these surrogates and their calibration against real hardware at high frequencies has been elucidated. In this paper we show how both lossy dielectric material and microstrip transmission line based "representative contents" can be designed and calibrated against real printed circuit boards over the frequency range 2-20 GHz using power balance concepts. The calibration is made by matching the average absorption cross-section of the surrogate to an average value for a class of real contents measured in a reverberation chamber. The surrogates are designed using efficient power balance models for layered media and field-excited microstrip lines and verified using full-wave simulation. The fabricated surrogates are validated by shielding measurements. The methodology presented could form an important part of future standards for enclosure qualification measurements that more accurately represent the internal environment of real equipment.

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Section: A Rc Shielding Measurementmentioning

confidence: 92%

Section: B Determination Of Aacsmentioning

confidence: 99%

Section: B Ram Based Recomentioning

confidence: 99%

mentioning

confidence: 99%

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Representative Contents Design for Shielding Enclosure Qualification From 2 to 20 GHz

Flintoft

Bale

Marvin

et al. 2018

IEEE Trans. Electromagn. Compat.

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“…IEEE Standard 299.1 contains an informative annex describing how to utilize absorbing materials in equipment enclosures for the measurement of shielding properties [5]. More recently, work has progressed to the consideration of higher frequencies using statistical approaches, particularly with regard to the effect of enclosure wall losses on shielding performance [6], [7].…”

Section: Introductionmentioning

confidence: 99%

Measured Average Absorption Cross-Sections of Printed Circuit Boards from 2 to 20 GHz

Flintoft

Parker

Bale

et al. 2016

IEEE Trans. Electromagn. Compat.

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Absorption by the contents of an equipment enclosure, particularly printed circuit boards (PCBs), affect the enclosure's shielding performance. At high frequencies, this absorption can be quantified using the angle of arrival and polarization averaged absorption cross-section (ACS). However, there is no available data on the high-frequency absorption characteristics of modern PCBs. In this study, we apply a reverberation chamber to the determination of the average ACS of a large number of PCBs taken from contemporary information and communication technology (ICT) equipment to provide a unique and comprehensive dataset. The ACS was found to range from 4 × 10 −4 -10 −2 m 2 from 2-20 GHz and different classes of PCB could be identified according to their surface characteristics. The "shadowing effect" of densely packed PCBs was also quantified for a subset of the PCBs. It was found that the ACS of a PCB in the stack was reduced by 20%-40% compared to its value when isolated. By way of a review of the general power balance analysis of an electrically large populated equipment enclosure in an external environment, we show how the acquired data will be useful for future qualification methodologies for ICT enclosures and PCBs.

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Extension and verification of absorbing material effectiveness on reducing electromagnetic emissions

Drake

Rajamani

Bunting

et al. 2015

2015 IEEE Symposium on Electromagnetic Compatibility and Signal Integrity

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Electronic devices, more specifically, devices enclosed inside cavities require special protection from sources of electromagnetic radiation. These include sources from outside and also sources that are co-located. This paper discusses experimental data obtained by measuring the absorbing effectiveness of materials of varying thickness. Results indicate that an increase in absorber surface area provides an overall better reduction in energy absorption while the increase in volume of the absorbing materials demonstrates little to no difference over one absorber.I.

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Effectiveness of absorbing materials on reducing electromagnetic emissions from cavities measured using a nested reverberation chamber approach

Cited by 4 publications

References 4 publications

Representative Contents Design for Shielding Enclosure Qualification From 2 to 20 GHz

Representative Contents Design for Shielding Enclosure Qualification From 2 to 20 GHz

Measured Average Absorption Cross-Sections of Printed Circuit Boards from 2 to 20 GHz

Extension and verification of absorbing material effectiveness on reducing electromagnetic emissions

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