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A susceptibility was identified experimentally when an external feature was added near an irregular aperture that spanned two faces of the shielding enclosure of an equipment under test. The susceptibility was due to a resonant response that occurred at a lower frequency than that expected by the resonances of the aperture, enclosure cavity, or external feature considered in isolation. Numerical modeling showed that currents induced on the exterior of the enclosure when the external feature is in place couple to the currents surrounding the aperture, leading to a longer resonant length than provided by the aperture alone. The resonant response giving the susceptibility was observed with various changes in aperture and external feature dimensions, provided that the aperture spanned two faces and the external feature was aligned with the enclosure edge that the aperture spanned. The low-frequency susceptibility can be mitigated by electrically connecting the external feature to the enclosure edge to interrupt the external current path. The higher-frequency resonant coupling due to the irregular aperture alone was not affected by the suppression of the external current.

Recently, there has been great interest in estimating the mean of the maximum field strength in a nested reverberation chamber in such conditions that the field coupled inside the equipment under test (EUT) deviates from the parent distribution, thus generating a non-Rayleigh distribution. For this purpose, a new regression model with the deep feedforward neural network is proposed to predict the mean of the maximum field inside a nested reverberation chamber configuration. In our proposed method, a frequency range that comprises the EUT in the overmoded regime is treated as an input of the network, and the mean of the maximum field is treated as the output of the network. Several networks with different numbers of hidden layers are trained, while adaptive learning rates and early stopping techniques are used to improve the network training process, subsequently reducing the uncertainties. After training, the networks are verified using a test set that is not implicitly employed during the training process. The testing and training mean-squared errors (625e-5 and 325e-5) with the network with five layers have a good agreement for a considered configuration, demonstrating a novel regression model that is able to rigorously extrapolate the mean of the maximum field in the other frequency steps that are not used in the training set.

In the framework of immunity testing, there has been recently a great interest to determine the maximum field distribution in a nested reverberation chamber, the inner cavity being considered as the equipment under test (EUT). The generalized extreme value distribution is a generalization of three asymptotic distributions that does not require knowledge of the field sample parent distribution in comparison with traditional method. It can therefore be applied in situations when the parent distribution is unknown, such as when an EUT is reverberant or is operating in the undermoded regime. In this paper, we present an experimental validation of the maximum statistical distribution of the internal field samples inside different nested cavity configurations. The Anderson–Darling test is applied to verify if a dataset is collected from a single statistical population inside the EUT with different stirring scenarios and two different EUT aperture dimensions. Parametric and nonparametric estimation are then used to model and to verify the results. The parametric and nonparametric distributions show good agreement for all test configurations considered, extending earlier works which considered reverberation-chamber fields themselves with no EUT included or did not include EUT internal stirring.

The effects of frequency stirring on the statistics of the currents induced on an equipment-under-test (EUT) placed in a reverberation chamber field are analyzed. A reciprocal approach that relates the received currents in a susceptibility test to the free-space input impedance presented by the EUT when excited at the test point is used. An analytical expression is then derived to give the distribution functions of the induced currents under frequency stirring that accounts for the frequency dependence of the EUT radiation characteristics. A numerical study of shielding-box EUTs with coupling apertures shows that the changes in the EUT test-port input impedance with frequency yield non-Rayleigh current statistics when frequency stirring is used. It is unlikely that a single distribution family with a limited number of parameters can be fit to the current statistics with EUTs of arbitrary volume, coupling aperture, and measurement probe configurations.

In the space community, there is increasing interest in adaption and augmentation of launch fairing thermal-acoustic blankets, to also control electromagnetic environment threats. This paper reports on the development of simulation methods to both optimize blanket materials for RF absorption and to provide quantitative guidance on their minimal spatial deployment inside the fairing. A stochastic power-balance model with multiple connected sub-cavities is used to map the reverberant electric field in the fairing when RF absorbing blankets are applied only locally – ie only partial coverage of the fairing wall. The sub-cavity Q factors resulting from different RF absorption blanket materials is calculated from published reflection loss data and a field incidence correction factor. Comparison with model-scale test data verified that the model correctly predicts the attenuation of different absorber materials, the spatial distribution of the field and the improvement in shielding effectiveness.

The electric field levels established at various points within a modeled rocket fairing under different excitations are measured. Both interior sources placed within different fairing sub cavities and exterior excitation was used. The effect of the addition of different absorbers on the electric field level in different sub cavities was investigated as well. The shielding effectiveness of the fairing within the different fairing sub cavities was considered. The relation between the total surface of absorber and the electric field level studied. In addition, the electric field level excited inside the fairing under external illumination was numerically simulated. The laboratory measurements were verified through comparison with the simulation results.

A launch vehicle payload fairing scale model has been designed, fabricated, and tested to investigate the reverberant electromagnetic fields within launch vehicle fairings. The fairing scale model uses a mechanical stirrer to attain statistically uniform fields within the fairing cavity. A removable payload model and payload adapter model are included in the fairing to study the interactions of fields with these structures. The layering of the fairing walls, use of shielding gaskets, and field probes to measure the cavity fields are described. The quality factor is measured when the fairing cavity is empty and when the surrogate payload and payload adapter models are added. The quality factor of the empty fairing measured from about 32 dB at 1 GHz to 41 dB at 6 GHz. The Q values dropped approximately 2 dB across the band when the payload and payload adapter models were placed in the fairing cavity. Measurements of Q at different probe positions within the fairing yielded similar results.

A study of the effect of the field-sampling probe configuration used in nested-cavity measurements has been performed. The outer cavity was an overmoded reverberation chamber and the inner cavity was a small conducting enclosure that included a coupling aperture. Mechanical stirring within both the external and internal cavities was combined with frequency stirring to yield the mean received signal. Monopole, meanderline, and log-periodic probes were evaluated. The three-dimensional meanderline probes overall showed the best performance, better sampling the low-frequency signals where the inner cavity is undermoded. Despite the advantages, the mean signals levels still show a dependence on the specific configuration of the meanderline used, particularly at low frequency, and care must be used in interpreting the measured levels.

The effects of cable routing within a shielding box has been evaluated using a numerical electromagnetic package. Different cable paths with both constant and varying lengths have proposed. The cable-feed port reflection coefficient and radiated electric field were considered for different test cases. The influence of slot apertures in the enclosure itself, gaps between external structures and the enclosure body, and cable route on radiated electric field and excited slot resonances are examined. The coupling between enclosure and cable resonances and their effects radiation emission are presented. The effect of the wire path on the slot resonances is also shown. The simulations for representative cases were empirically verified through comparison with laboratory measurement.

Measurement of the quality factor of a reverberation chamber has been examined using numerical simulation and experimental measurements. The numerical simulations demonstrate that common frequency-domain and time-domain approaches yield the same measured quality factors, provided that the measurement bandwidths of each approach are equal and the frequency-domain measurements are accurately compensated for antenna-efficiency effects. Measurements performed using intentionally mismatched antennas eliminate the antenna loading effects and give the quality factor of the chamber itself. The experimental validation confirms that the frequency-domain and time-domain approaches yield the same measured quality factors under practical conditions when the antennas are well-to-moderately matched. However, the accuracy of the frequency-domain measurement is compromised when large antenna-efficiency compensation must be applied when using poorly matched test antennas. The narrowband time-domain approach with poorly matched antennas provides consistent and repeatable measurements of the quality factor of the chamber itself without antenna loading effects.

The statistics of the current induced on conducting wires and surfaces within a partially shielded enclosure by aperture coupling of an ideally random, mechanically stirred reverberation chamber electromagnetic field has been considered. A robust discretization of the plane-wave spectral representation of the chamber field confirms that the magnitude of the induced current at a test point follows a Rayleigh distribution provided that the equipment under test (EUT) is composed entirely of electromagnetically linear materials and mechanical or spatial stirring of the external chamber field is used, independent of the sizes of the EUT and coupling aperture. The discrete spectrum gives an efficient method to numerically find the statistics of the currents on or within arbitrarily shaped EUTs. Experimental measurement of the induced currents on a sample EUT within a mechanically stirred reverberation chamber confirms the validity of the discrete-plane-wave spectral method of predicting the current statistics at low and high frequencies. Addition of frequency stirring introduces a fundamental difference in the operation of a reverberation chamber test that leads to non-Rayleigh sample statistics when highly resonant EUTs are considered.

The external noise immunity of a real structure’s scale model has been studied. Using the scale model improves the accuracy and reduces the convergence time of numerical simulation. Different coupling paths into the structure were investigated using the Computer Simulation Technology (CST) electromagnetic simulation software. The effects of slot, aperture-slot, and gap-slot coupling apertures on the shielding performance of the scale model are the same as for the real tunnel box. The simulation results were experimentally verified through three different measurement setups.

Analytical expressions for uncertainties introduced into reverberation chamber field intensity measurements due to imperfect knowledge of the mean field level are derived. Expressions for the normalized root-mean-square error in estimates of the mean field level show that the maximum-likelihood estimation approach is superior to direct averaging of field samples, independent of the number of samples used in the estimate. The probability distribution functions of the ratio of test-field-sample to estimated-mean are then derived, both for the case where the test sample is an additional independent measurement and when the test sample was used in performing the mean estimation. The distributions give a direct representation of the effects mean field level uncertainty on the sample-to-mean ratio statistics. The expressions are general for both one-axis and three-axis field-intensity measurements.

In this paper, the immunity of a tunnel box shielding structure against external electromagnetic noise has been studied. The electromagnetic susceptibility of the structure has been characterized by determining different coupling paths into the system. Computer Simulation Technology (CST) electromagnetic simulation software was used for all simulation. The effects of slot, aperture-slot and gap-slot on shielding performance have been studied. The simulation results were verified through measurement.

In this paper, off-body ultra-wide band (UWB) channel characterization and modeling are presented between an unmanned aerial vehicle (UAV) and a human subject. The wearable antenna was patched at nine different body locations on a human subject during the experiment campaign. The prime objective of this work was to study and evaluate the distance and frequency dependent path loss factors for different bandwidths corresponding to various carrier frequencies, and also look into the time dispersion properties of such unmanned aerial vehicle-to-wearables (UAV2W) system. The environment under consideration was an indoor warehouse with highly conductive metallic walls and roof. Best fit statistical analysis using Akaike Information Criteria revealed that the Log-normal distribution is the best fit distribution to model the UWB fading statistics. The study in this paper will set up a road map for future UAV2W studies to develop enhanced retail and remote health-care monitoring/diagnostic systems.

Estimating the electromagnetic field strength in avionics boxes and other small enclosures at the design stage requires an estimate of the Q factor of the cavity modes. When the enclosure is small, it is typically under-moded so that Q measurement techniques which are standard practice in over-moded reverberation chambers may not be a robust measure. Furthermore, practical antenna used to measure Q in a small cavity may have a strong influence on the result obtained, as reported by Tait et al, IEEE Trans. EMC 55 2 2012. This paper reports the results of testing to determine the Q factor of a small aperture enclosure, used in a statistical power balance model to predict the electric field strength. The contributors to the total Q are identified. A novel S 11 curve fitting method to measure modal Q is introduced and compared with the time domain method for measuring Q.

The generalized extreme value distribution has been recently presented as a leverage to find the maximum distribution function directly without a knowledge about the parent distribution. In this paper, this key component is investigated when the parent distribution is not known. The measurement is performed inside a nested chamber with different aperture dimensions and shapes on the enclosure. The Anderson Darling test is applied to show the field does not follow Rayleigh distribution. The results are shown by using parametric and non-parametric estimation in the confidence interval.

A brief presentation on how to solve using the finite element method and the application of the method to microstrip problem are discussed.

The effects of aperture dimension on the maximum field distribution function in the nested chamber were investigated. The maximum distribution was calculated directly by applying the generalized extreme value (GEV) distribution regardless of the parent distribution. The purpose of this paper is to show how aperture dimensions affect the maximum field distribution by changing the dependence of the environment within the box on the big chamber. Maximum likelihood is used to estimate the parameters of the distribution and parametric and non-parametric estimation are used to model and to verify the results.

A dual band FSS based on array of double square ring shaped resonators has been proposed. The proposed structure represents a wide-angle perfect rejection of incidence wave and polarization independency. The rejection occurs at two different resonant frequencies as high as 98% and 99%, at 2.45(GHz), 5 (GHz) respectively. The proposed Frequency Selective Surface has designated for blocking the WI-FI signals and screen room applications. Simulation results show polarization independency for both rejection bands.

Committees of multilayer neural networks were used to estimate the appropriate surface area and thickness of RF absorbing material needed to achieve a desired quality factor (Q) inside a reverberation chamber. The networks were trained with Bayesian Regularization to avoid overfitting. Monte Carlo cross-validation was used to develop confidence bounds on the accuracy of the network committees.

A previously introduced numerical approach to modeling a susceptibility test within a reverberation chamber has been validated against experimental measurement. A sample equipment-under-test (EUT) was fabricated and tested within a reverberation chamber over a large frequency band. The scattering parameter between the source antenna and the EUT measurement port measured within the chamber over a large number of mechanical tuner steps is used to derive an estimate of the mean current magnitude excited on a probe within the EUT by a random chamber field of given RMS level. The numerical simulations were performed using a moment-method based technique accelerated by the fast multipole method. The numerically simulated and measured currents agree very well over the measured band, confirming the validity of the numerical approach for test equipment ranging in size from large to small compared to the electromagnetic wavelength.

The dependence of the quality factor (Q) of a reverberation chamber as measured using a time-domain approach on the total bandwidth included in the time-domain signal has been investigated. Time-domain measurement of the Q factor of a mechanically stirred, metal cavity has been been performed using synthesized pulses of different bandwidth with the cavity both loaded and unloaded by absorbing material. The results show that the bandwidth does not need to be sufficiently large to give an equivalent pulse duration that is shorter than the wall scattering time to give an accurate measurement of the quality factor.

This study investigates the measurement of current on a wire located inside a cavity with an aperture as a function of excitation frequency with the use of a simple S parameter model. Validation is provided by comparing simulations and measurements. Using this approach, it will be possible to make an accurate prediction of the current distribution on the wire, and thereby to describe potential interference effects to equipment placed along the wire bundle at frequencies of interest.

This paper introduces a new artificial neural networks (ANNs)-based reverse-modeling approach for efficient electromagnetic compatibility (EMC) analysis of printed circuit boards (PCBs) and shielding enclosures. The proposed approach improves the accuracy of conventional or standard neural models by reversing the input-output variables in a systematic manner, while keeping the model structures simple relative to complex knowledge-based ANNs (e.g., KBNNs). The approach facilitates accurate and fast neural network modeling of realistic EMC scenarios where training data are expensive and sparse. To establish accuracy, efficiency, and feasibility of the proposed reverse-modeling approach, PCB structures such as perforated surface-mount shields and partially shielded PCB traces are treated as proof-of-concept examples. Although the modeling examples presented in the paper are based on training data from EM simulations, the approach is generic and hence valid for EMC modeling based on the measurement data. The approach is particularly useful in the electronic manufacturing industry where PCB layouts are frequently reused with minor modifications to the existing time-tested designs.

The use of Feature Selective Validation (FSV) in validating the current induced on a wire inside a highly resonant cavity environment by an incident plane wave in the frequency range from 300 MHz to 8.5 GHz is examined. FSV gives fair agreement between measured and simulated results. A visual comparison of the responses suggests that the agreement is better than fair. When comparing the results of different numerical simulations of the same problem, FSV was sensitive to slight differences in the position of current probe and different mesh structures that give a small difference in the amplitude of the induced current, but its validation results are similar to the opinion of experienced researchers. FSV proved to be highly sensitive to slight offsets in the frequency of resonant responses due to modeling or physical geometry differences, potentially limiting its application to problems of this type.

This paper discusses the results of exploratory research in analyzing the electromagnetic compatibility (EMC) of commercially available radio frequency transceivers co-located within the chassis of an Unmanned Air System (UAS). Tests were performed on a UAS with multiple communication systems onboard encompassing frequency bands with center frequencies of 915 MHz, 2.4 GHz, and 5.8 GHz. These tests were performed in a normal operational environment a.k.a free space and also inside a multipath environment where the UAS was subjected to performance evaluation i.e. the status of the communication systems of the UAS were monitored while there is no external EM threat and also while applying an external EM field.

An in-silico (numerical) study of the measurement of the quality factor (“Q”) of a reverberation chamber has been performed using an efficient moment method based on the cavity Greens function. Antenna mismatches directly reduce the Q measured in the frequency domain but not in the time domain. Well matched antennas load the chamber more severely than mismatched antennas and yield lower measured quality factors, particularly at lower frequencies. Quality factors measured in the time domain are approximately equal to the mean of the frequency-domain Qs averaged across the pulse bandwidth and are therefore less affected by non-ideal field distributions in chambers operating at low frequency.

Continuous stirred-mode operation of a mechanically tuned reverberation chamber provides an alternative to stepped-mode operation that is both more cost effective and more robust in many electromagnetic compatibility testing applications. An experimental investigation shows that the spectral information available within the chamber is the same for both the stepped and the stirred operation and is independent of the tuner speed provided that the chamber transient time is small compared to the rate at which the fields change inside the chamber due to the tuner rotation. This is further confirmed for stirred operation at additional frequencies. However, the field must be properly sampled to ensure that all independent field configurations available at the test point within the chamber are included in the spectral analysis. Optimal sampling is obtained when sampling at the same tuner angular position increment over a single tuner rotation at any tuner speed. Equipment under test may be exposed to all available field configurations available within the chamber using stirred operation with a single rotation of the tuner, giving a more robust test than the minimum 12 steps that are used with the stepped operation. Testing time is also reduced. The exposure time to a particular field configuration can be controlled with knowledge of the number of independent samples available in the chamber and by changing the tuner rotational speed.

A novel wire antenna for future dedicated short range communications vehicle-to-vehicle communications is introduced. The proposed antenna carries low-profile and low-cost features, and possesses an improved gain performance. This article also includes a specific feed network design for the proposed antenna to meet the mechanical and manufacturing requirements. Two different numerical techniques using CST Microwave Studio and HFSS have been applied for evaluating the performance of the proposed antenna. The whole system including the feed network and the antenna elements is integrated, and its performance is also assessed. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013. © 2013 Wiley Periodicals, Inc.

An electromagnetic susceptibility test within an ideal reverberation chamber is numerically simulated using the moment method (MM). The random field environment within the chamber is synthesized using a superposition of plane waves that are propagating in fixed directions determined rigorously from spectral sampling theory. Randomness is introduced in the complex field amplitudes associated with each plane wave. This approach yields field statistics within a designated test region that approach ideal. Moreover, the fixed propagation directions allow very efficient calculation of the currents induced at specific test points on an equipment-under-test due to the random field realizations. MM calculations show that the proposed sampling method yields a better prediction of the statistics of the induced current while requiring far less computation time than the currently used technique of superimposing randomly propagating plane waves to yield field realizations.

Background Recently, there has been a shift from using lecture-based teaching methods in undergraduate engineering courses to using more learner-centered teaching approaches, such as problem-based learning. However, research on the impact of these approaches has mainly involved student perceptions of the teaching method and anecdotal and opinion pieces by faculty on their use of the teaching method, rather than empirically collected data on students' learning outcomes. Purpose (Hypothesis) This paper describes an investigation of the impact of problem-based learning (PBL) on undergraduate electrical engineering students' conceptual understanding and their perceptions of learning using PBL as compared to lecture. Design/Method Fifty-five students enrolled in an electrical engineering course at a Midwestern university participated in this research. The study utilized a within-subjects A-B-A-B research design with traditional lecture as the baseline phase and problem-based learning as the experimental phase of the study. Participants completed pre- and post-tests surrounding the four topics covered in the study and also completed a Student Assessment of Learning Gains (SALG) survey. Result Results suggested participants' learning gains from PBL were twice their gains from traditional lecture. Even though students learned more from PBL, students thought they learned more from traditional lecture. We discuss these findings and offer implications for faculty interested in implementing PBL. Conclusion Given the limited research on the beneficial effects of PBL on student learning, this study provides empirical support for PBL. We discuss findings from this study and provide specific implications for faculty and researchers interested in problem-based learning in engineering.

This paper presents a transrectal dual-modality near-infrared (NIR) diffuse optical tomography technique coupled with ultrasonography that provides an integrated method for detecting prostate cancer (PCa). The study that provides an alternative transrectal prostate imaging system stems from the perceived inadequacy of conventional transrectal ultrasound (TRUS) in PCa imaging. The transrectally applied diffuse optical tomography aims to characterize the spatially resolved optical properties of the intact prostate that are known to have intraorgan and intersubject heterogeneities. A canine model of PCa using canine transmissible venereal tumor was used to demonstrate the utility of this technology in detecting PCa. Tumors in the pelvic canal, including tumors in the prostate, were found to be detectable at 2-week postinjection based upon the NIR absorption contrast, which was detected a few weeks earlier than using NIR-reduced scattering and effective attenuation contrasts, as well as TRUS. Transrectal optical tomography detection of cancerous tissues in vivo in intact canine prostate based upon NIR contrasts may prove useful for diagnostic imaging of PCa and potentially aid in pretreatment planning for phototherapy applications.

This is the first tomography-presentation of the optical properties of a normal canine prostate, in vivo, in its native intact environment in the pelvic canal. The imaging was performed by trans-rectal near-infrared (NIR) optical tomography in steady-state measurement at 840 nm on three sagittal planes across the right lobe, middle-line, and left lobe, respectively, of the prostate gland. The NIR imaging planes were position-correlated with concurrently applied trans-rectal ultrasound, albeit there was no spatial prior employed in the NIR tomography reconstruction. The reconstructed peak absorption coefficients of the prostate on the three planes were 0.014, 0.012, and 0.014 mm-1. The peak reduced scattering coefficients were 5.28, 5.56, and 6.53 mm-1. The peak effective attenuation coefficients were 0.45, 0.43, and 0.50 mm-1. The absorption and effective attenuation coefficients were within the ranges predictable at 840 nm by literature values which clustered sparsely from 355 nm to 1064 nm, none of which were performed on a canine prostate with similar conditions. The effective attenuation coefficients of the gland were shown to be generally higher in the internal aspects than in the peripheral aspects, which is consistent with the previous findings that the urethral regions were statistically more attenuating than the capsular regions.

The Quality factors of an empty and loaded reverberant cavity were measured using time domain techniques. Measurements were performed for a set of frequencies under different loading conditions achieved by varying the material type and material amount. The measured data were used to develop an artificial neural network (ANN) model that predicts the amount of material required for a desired change in Q at a certain frequency for the cavity under consideration. The results show good comparison between the measured and the predicted values, thereby supporting the benefit of the ANN paradigm for studies like this, where experiments tend to be expensive.

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.

This paper discusses the validation of Modal/method of moments (MoM) including cases when the apertures are made as big as the wall of the enclosure (equivalent to having one side of the cavity open). The validation is done using field computations involving bodies of arbitrary shape (FEKO), a commercially available code. The results show that Modal/MoM predicts the results close to the analytical results of Robinson et al. Electron. Lett., 32 (17), 1996; Robinson et al., IEEE Trans. Electromagn. Compat., 40 (3), 240-247, 1998 for single-aperture cases and for most double-aperture cases. Also, for the cases of considering oblique incident plane waves, through validation, it has been found that Modal/MoM can predict the shielding effectiveness close to measured results for smaller angles and not for larger angles of incidence due to the edge effects. In this work, the shielding effectiveness is calculated at only one point, the center of the cavity assuming it to be the worst case. This work discovers the limitation of Modal/MoM for certain applications.

Shielding effectiveness of metallic enclosures with apertures when illuminated by an oblique incidence arbitrary polarized plane wave has been studied by using an efficient hybrid modal/moment technique. Shielding effectiveness of rectangular enclosures with one, two, and four apertures at multiple points inside the enclosures for various frequencies has been calculated when the illuminating source flies by the front of the enclosure. The work shows that the shielding effectiveness is seriously affected by frequency, angle of incidence and polarization of the illuminating field; the number and orientation of apertures; and the location inside the cavity. It has been shown that the usual assumption about the normal incidence being the worst-case scenario for shielding effectiveness values may not be valid when there is more than one aperture in the cavity. The paper emphasizes the need for the statistical investigation of shielding effectiveness problem of metallic enclosures with apertures.

This paper emphasizes the application of numerical methods to explore the ideas related to shielding effectiveness from a statistical view. An empty rectangular box is examined using a hybrid modal/moment method. The basic computational method is presented followed by the results for single- and multiple-observation points within the over-moded empty structure. The statistics of the field are obtained by using frequency stirring, borrowed from the ideas connected with reverberation chamber techniques, and extends the ideas of shielding effectiveness well into the multiple resonance regions. The study presented in this paper will address the average shielding effectiveness over a broad spatial sample within the enclosure as the frequency is varied.

This paper introduces the special issue of the 2015 symposia for IEEE EMC held in Santa Clara, CA, USA and Dresden, Germany.

A reverberation chamber is an enclosure consisting of metal walls with a metallic paddle wheel (denoted as a "stirrer" or "tuner") forming a high quality-factor (Q) cavity with continuously variable boundary conditions. Reverberation chambers are attaining an increased importance in determining the electromagnetic susceptibility of avionics equipment. Given the nature of the variable boundary condition, the ability of a given source to couple energy into certain modes and the passband characteristic due the chamber Q, the fields are typically characterized by statistical means. The emphasis of this work is to apply finite-element techniques at cutoff to the analysis of a two-dimensional structure to examine the notion of shielding-effectiveness issues in a reverberating environment. Simulated mechanical stirring is used to obtain the appropriate statistical field distribution. The shielding effectiveness (SE) in a simulated reverberating environment is compared to measurements in a reverberation chamber. A log-normal distribution for the SE is observed with implications for system designers. The work is intended to provide further refinement in the consideration of SE in a complex electromagnetic environment.

The statistical characterization of a simulation reverberation chamber is performed by considering a two-dimensional finite element model. This model includes a source to study the particular modal fields that couple into either a transverse electric or transverse magnetic configuration. The analysis includes a characterization of the basic field statistics, max-to-average ratio, normalized standard deviation, stirring ratio, and field uniformity. The shielding effectiveness of an aperture is studied that provides some insight into the nature of the fields coupled from a complex to a noncomplex environment.

Electromagnetic interference can hinder the operations of systems near the source of the interference. This paper details the process of using a nested reverberation setup in order to determine the absorptive effectiveness of several absorbing materials. Results show that the position of absorbing materials is inconsequential as long as they are placed outside of the working volume and away from wall joints of the cavity given that the cavity is overmoded and the cavity under consideration produces a well stirred environment during normal operation.