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The evaluation of the shielding effectiveness (SE) of rectangular metallic enclosures having apertures in their walls and loaded with conducting bodies is the subject of this paper. The conducting objects can be either modifications of the inner part of the enclosure (e.g., simple metal plates or protrusions of the walls) or elements to be protected from external fields (e.g., printed circuit boards or metallic boxes). The SE of such enclosures is thus investigated through an efficient integral formulation based on the method of moments. The proposed approach makes use of a very fast computation of the enclosure Green's functions, based on the Ewald representation and interpolation techniques. The analysis shows that the classical SE of enclosures (calculated when a uniform plane wave impinges on the aperture of an empty enclosure) can be a very tricky figure of merit since the field inside the shield can be seriously affected by the possible presence of 2-D or 3-D conducting loads, especially in the frequency range above the first resonant frequency of the aperture-enclosure system. Comparisons with full-wave results obtained through different commercial software confirm the validity of the proposed technique and its excellent performance. Index Terms--Green's function, integral equations, interpolation, loading, metallic enclosures, method of moments (MoM), shielding effectiveness (SE).

A method is presented for the measurement of shielding effectiveness of planar materials with nonconducting surfaces such as carbon fiber composites. The method overcomes edge termination problems with such materials by absorbing edge-diffracted energy. A dynamic range of up to 100 dB has been demonstrated over a frequency range of 1-8.5 GHz, depending on the size of the sample under test. Comparison with ASTM D4935 and nested reverberation measurements of shielding effectiveness shows good agreement. Index Terms--Composite materials, shielding effectiveness, shielding measurements.

A generalized mathematical procedure is developed for investigating shielding performance and inner wideband pulse responses of metallic rectangular multistage cascaded enclosures with multiple rectangular apertures, which is illuminated by an electromagnetic pulse (EMP). The mathematical methodology is based on the integral equation technique combined with the method of moments, by which all unknown aperture fields are solved according to a set of linear algebraic equations of infinite order. Numerical computations are performed to show frequency-and geometry-dependent shielding effectiveness and inner pulse waveforms of single-and double-stage cascaded enclosures, respectively, with computational accuracy and convergence rate also checked. It is found that using appropriate metallic multistage cascaded enclosures, high shielding performance can be achieved, which can provide an effective protection for certain electronic and communication systems from the interference of an EMP. Index Terms--Electromagnetic pulse (EMP), inner pulse responses, intentional electromagnetic interference (IEMI), metallic rectangular multistage cascaded enclosures, method of moments, multiple apertures, shielding effectiveness.

The numerical code is developed for analyzing the time evolution of the shielding current density in the high temperature superconductor (HTS) thin film. The results have computations show that the maximum repulsive force is roughly proportional to the critical current density.

The magnetic field in the Superconducting RF Test Facility (STF) vacuum vessel for the 45 MV/m cavity is measured. The results are presented along with the permeability measurement data, which is used for estimating the shielding effect when the cryomodules are cooled down to the operating temperature.

The numerical code is developed for analyzing the time evolution of the shielding current density in asymmetric high temperature superconducting (HTS) thin films by using the EFG method. The results have shown that the spatial distribution of the shielding current density is calculated with very high accuracy.

Three-dimensional (3-D) hexahedral finite element method (FEM) was used for examining the current distribution and AC loss in each shield layer of the co-axial multi-layered High Temperature Superconducting (HTS) power cable. Findings revealed that the current distribution in the shield layers can be controlled by adjusting the pitches of shield layers.

The attenuation coefficient of a rectangular dielectric line enclosed by a rectangular shield is obtained by the use of a rigorous mode-matching method to calculate the required mode field intensity. The cross section of the waveguide is overlaid by a grid, and numerical integration is used to determine the power flow, dielectric, and conductor losses and respective attenuation coefficients. To obtain experimental verification, a length of waveguide was made into a resonator, and measured and calculated Q factors were compared. The results for the [E.sup.y.sub.11] mode show how the influence of the shield decreases with distance. This is relevant to the design of dielectric waveguide structures and in filter applications where dielectric resonators are used. Index Terms--Attenuation, dielectric waveguides, mode-matching methods, numerical analysis, shielding.

A novel wideband monopole antenna integrated within the front-end module package for WLAN and/or WiMAX operation in the 5 GHz band for a mobile device is presented. The front-end module package mainly comprises a bent [pi]-shaped wideband monopole antenna for 5 GHz band operation and a shielding metal case for accommodating the associated module and circuitry. The antenna is integrated to the shielding metal case through short-circuiting. For practical applications, the proposed front-end module package is to be mounted at one of the corners of the system circuit board of the mobile device. In this case, the shielding metal case not only performs as part of the ground plane of the antenna, but also functions as a shielding metal block to shield the antenna from the undesired coupling with nearby electronic or conducting elements in the mobile device. The proposed design of the front-end module package with an embedded antenna is studied, and obtained results of the constructed prototypes are presented. Index Terms--Antennas, internal mobile antennas, integrated mobile antennas, wideband mobile antennas, WLAN antennas, WiMAX antennas.

An improved subcell model is presented for including thin material sheets method in the finite-difference time-domain (FDTD) method. This improved subcell can be used to simulate a thin magnetic ([[micro].sub.s] [not equal to] [[micro].sub.o]) sheet. Then, the improved subcell model is applied to the analysis of the shielding effectiveness (SE) of the electromagnetic wave propagating through a thin infinite material sheet, which is verified by comparison with the analytical results. Updated equations for components of the field on special spatial grids which are on edges and corners of the enclosure are presented, and the subcell model is used for the analysis of a thin-walled enclosure with an aperture. The FDTD results are in very good agreement with the test results. Index Terms--Enclosure with an aperture, shielding effectiveness (SE), subcell model, thin material sheet.

The purpose of this paper is to investigate the use of equivalent-layer models for the analysis of carbon-fiber composite materials. In this paper, we present three different models for the electromagnetic characterization (effective material properties) of fiber composites that are commonly used in aircraft and EMC/EMI shielding materials. These three models represent various orders (or levels) of detail in the fiber composite structure and, hence, capture various physical aspects of the composite. These models can be used to efficiently calculate the reflection and transmission coefficients, as well as the shielding effectiveness, of these fiber composites. We compare results of the reflection coefficient and shielding effectiveness obtained from these effective-property models to results obtained from a full numerical solution based on the finite-element (FE) method of the actual periodic fiber composite. We show that, as expected, as more of the geometric detail of the fiber composite is captured with the different models, the upper frequency limit of validity increases. Index Terms--Carbon fiber composites, effective material properties, effective media, homogenization, shielding effectiveness, shielding materials.

The moment method coupled with the uniform theory of diffraction is employed in this paper to simulate the electromagnetic shielding performance of an enclosure with apertures residing in a very large platform, in which the moment method is used to accurately model the enclosure with apertures, and the influence of the large platform is efficiently calculated by using the uniform theory of diffraction. These two methods are coupled through the tangential electromagnetic fields on the apertures of the enclosure. In this paper, the accuracy of this coupled method developed is validated, and we apply this method for simulating the shielding effectiveness with the sources inside/outside the enclosure. The simulation results show that this coupled technique is able to simultaneously model the effects of the smaller structures and the large platform on the total electromagnetic property. It further demonstrates that this coupled method is a very flexible and powerful technique for analysis of the electromagnetic compatibility problems with smaller objects mounted on a larger platform. Index Terms--Electromagnetic shielding simulation, moment method (MM), uniform theory of diffraction (UTD).

In this paper, a moment method (MM) solution for analyzing the electromagnetic (EM) shielding properties of three-dimensional (3-D) lossy dielectric and magnetic objects over a lossy half space is presented. An MM, based on a volume formulation and a special Green's function in the spectral domain, is developed. Plane waves with TMz and TEz polarizations incident upon 3-D lossy material structures are demonstrated for the shielding effects of those bodies in the presence of a lossy ground. Some of the results are compared with those evaluated by applying the finite difference time domain method, and good agreements are obtained. The MM solution can be used to study the shielding problems for 3-D objects located above a lossy ground. Index Terms--Lossy half space, moment method (MM), spectral domain, shielding, three-dimensional (3-D) object.

This paper presents an intermediate level circuit model (ILCM) for the prediction of the shielding effectiveness (SE) of a rectangular box containing a rectangular aperture, irradiated by a plane wave. The ILCM takes into account multiple waveguide modes, and is thus suitable for use at high frequencies and/or relatively large boxes. Inter-mode coupling and reradiation from the aperture are taken into account. The aperture may be positioned anywhere in the front face of the box, and the SE at any point within the box may be found. The model is presented in such a way that existing ILCM techniques for modelling elements such as monopoles, dipoles, loops, or transmission lines may be seamlessly incorporated into the circuit model. Solution times using the ILCM technique are three orders of magnitude less than those required by traditional numerical methods such as FDTD, TLM, or MoM. Accuracy however is not significantly compromised. Comparing the circuit model with TLM over nine data sets from 4 MHz to 3 GHz resulted in an rms difference of 7.70 dB and mean absolute difference of 5.55 dB in the predicted SE values. Index Terms--Aperture in box, circuit model, multiple modes, shielding effectiveness.

Complex RSFQ circuits are typically dc-biased with one or more current bias trees, with current returning through a superconducting ground plane. Current and field distributions are modeled to show that magnetic field and flux are indeed important.

The multilevel fast multipole moment method is employed to compute the electromagnetic coupling and shielding of various aperture-coupled metallic enclosures. A phenomenological study of electromagnetic coupling, due to various slot shapes and sizes, with or without the presence of wire penetration is conducted. These slots are situated on over-moded cavities and two methods are proposed to mitigate slot coupling into the cavity's interior. As part of this work, we also investigate the coupling through similar slots and apertures within a complex platform such as an automobile. The proposed methods have shown to increase shielding by as much as 5-35 dB within the frequency range of interest. Index Terms--Automotive electromagnetic compatibility (EMC), electromagnetic interference (EMI), method of moments (MOM), multilevel fast multipole moment method (MLFMM), numerical modeling, shielding methods.

The inductance of a coil in a slotted, conducting shell is investigated. At frequencies for which the coil is very small relative to wavelength, an integral equation is formulated and numerically solved for the electric field induced in the slots. From knowledge of the slot electric field, the inductance of the coil in the slotted shell can be calculated. The dependence of inductance on the presence of the slotted shell is assessed quantitatively and explained on the basis of physical principles. The inductance of a one-turn loop inside a slotted shell is measured, and the data are found to be in excellent agreement with computations. As an unslotted shield closes on a coil, inductance is reduced noticeably, but if the shield possesses axial slots, the reduction is much less significant. Index Terms--Apertures, coils, equations, inductance, integral.

In this paper we present the basis for the analysis of shielded tuning networks coupled to wire antenna elements. The structure analyzed comprises three conducting cylindrical tubes that form an aperture-fed circular coaxial waveguide. Two methods are presented for formulating and solving integral equations for the structure. The first method is based on the mixed potential electric field integral equation enforced on the three cylindrical tubes, and the second is based on aperture theory. An end correction capacitance is used to adjust the reflection coefficient in the eigenmode expressions of the aperture method. The data obtained by the two methods are in close agreement. Differences in actual currents and equivalent currents obtained from solutions are discussed and reconciled. Index Terms--Apertures, coaxial transmission line discontinuities, coaxial waveguides, cylindrical antennas.

This paper describes a simple extension of the sheet impedance concept to treat electromagnetic (EM) shields that may be thick in terms of material shield wavelengths. For magnetic shields, a simple relation between the equivalent electric and magnetic currents representing the shield is obtained, and the electric current is found as the solution of a single surface integral equation that is shown to be a simple perturbation of that for a perfect electric conducting (PEC) surface. Finally, it is shown that the computation of the small interior fields of good shields requires the use of the proper PEC interior equivalent problem. Index Terms--Method of moments, sheet impedance, shielding.

A numerical method is proposed to model transients in a shielded cable embedded in a three-dimensional field domain by using the finite-difference time-domain (FDTD) method. The coaxial shielded cable is assumed to be a multiconductor transmission line (MTL). The in cell voltage and the current on the external shield surface are calculated by a full-wave method, while the core current and the core-to-shield voltage are analyzed by assuming the validity of the quasi-TEM propagation mode inside the shield. The internal and external shield surfaces are coupled by the transfer admittance and by the transfer impedance of the cable shield. The solution is obtained by the FDTD method combining the MTL equations with the field equations. The proposed time-domain method takes into account the frequency-dependent parameters of the cable conductors by recursive convolution techniques. The validation of the procedure is performed in simple test configurations. Index Terms--Electromagnetic compatibility/interference (EMC/EMI), finite-difference time-domain (FDTD) method, multiconductor transmission lines (MTL), shielded cables.

Recently, the impedance boundary conditions (IBCs) for thin conductive and highly permeable shieldings have been extended to' nonlinear material characteristics, which are modeled by the effective permeability. In this paper, the coupling of these nonlinear IBCs with the finite-element method (FEM) outside the shielding material is improved. Index Terms--Coupling with finite-element method (FEM), effective reluctivity, nonlinear impedance boundary conditions, thin nonlinear shielding.

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 will be studied that will provide some insight into the nature of the fields coupled from a complex to a noncomplex environment. Index Terms--Electromagnetic compatibility, finite-element methods, mode-stirred chambers, reverberation chambers, statistical electromagnetics.

A comparative study has been made of the use of a noncontact probe method and the dual TEM cell method for the measurement of the surface impedance of composite materials. The results show that the values of surface impedance obtained by the two methods are in substantial agreement when the samples are pseudo-isotropic. Very different results are obtained by the two methods, however, when the samples are anisotropic because the two techniques induce a different flow of current (circular in the case of the noncontact probe method and laminar in the case of the dual TEM method). Comparison of the results from the two methods has shed light on the structure of carbon composite materials. Index Terms - Graphite, materials testing, resistance measurement, shielding.

A generalized potential-matching method incorporating reflection matrices is developed to calculate the capacitance of microshield lines with trapezoidal, circular, and V-shaped shields. Both completely shielded and half-shielded lines are analyzed. The effects of membrane thickness, strip width, and gapwidth on the characteristic impedance are studied. Index Terms - Capacitance, layered medium, microshield lines, potential-matching, reflection matrix.

High current carrying cables used in power transmission lines create strong magnetic fields in their vicinity. For ac lines at 50-60 Hz, the magnetic field is quasi-static and hence uncoupled from the electric field. Shielding of such low frequency magnetic fields is a challenge. In this paper, finite element modeling is used to study the effect of various shield geometries and shield materials around a current carrying wire. Two-dimensional analysis is sufficient: for this problem because the cables are very long compared to the wire diameters. Shielding effectiveness, defined as the difference in the magnetic field intensity with and without the shield, is presented. It is concluded that a partial shield is the optimal design for shielding the region below the cable. To achieve this, the shield gap must be oriented above the high current wire. Index Terms - Finite element modeling, magnetic fields, power lines, shielding.

Power frequency magnetic fields are difficult and expensive to shield, particularly when the fields originate from sources with complicated field patterns. A method is discussed and test data presented which suggests that carefully combining active and passive shielding techniques can produce results which are importantly superior to either technique when used alone. The results are generally consistent with an analysis which considers sources as a superposition of elementary source fields with different order terms. Key Words - Magnetic Fields, Active Field Cancellation, Passive Shielding.

This paper presents a time domain approach for the analysis of the coupling between an electrostatic discharge (ESD) current and the internal region of a shielded enclosure with a slot. The application of the equivalence principle allows us to obtain an integro-differential equation for the unknown distribution of the aperture electric field. The numerical solution is obtained by an iterative procedure developed by the method of moment (MoM) in time domain. The approach is also applied at the case of a transient incident field of a plane wave impinging on the enclosure. The use of proper impulse responses for space and cavity regions make the model efficient from a computational point of view, without losing in accuracy. Theoretical results are validated by measurements. Index Terms - Electrostatic discharge, metallic enclosure, method of moment in time domain, slot.

A theoretical model is proposed to study the near-field shielding and reflection characteristics of anisotropic laminated planar composites. Specifically, the plane-wave spectral representation is used to express the dipole field and the wave-transmission matrix technique is employed to deal with the transmitted and reflected fields. In this study, numerical results for graphite/epoxy (G/E) and boron/epoxy (B/E) composites are presented to discuss, in detail, the effects of varying the observation distance, number of layers, lamina thickness, fiber conductivity, and fiber orientation pattern. Comparison with the measured results and the previous published ones are also included to confirm the accuracy of this proposed model. Index Terms - Composite materials, near-field shielding.

A method is described for calculating the induced current distribution within a thin, nonferrous conducting plate with finite dimensions in the presence of an imposed magnetic field due to specified source conductors. The induced current solution is used to evaluate the resultant shielded magnetic field. In contrast with three-dimensional finite element descriptions, the method is applicable and computationally efficient for the complicated imposed field distributions that are typically present in practical shielding applications. Calculated results are compared with measured results for an experimental setup in which source conductors carry time-varying currents in opposite directions on one side of an aluminum plate, with the field magnitudes determined on the opposite (shielded) side of the plate. The calculated and measured results are in good agreement, both when the aluminum plate is present and when it is absent. This good agreement extends to regions where end effects yield very significant departure from the results of a 2-D finite element eddy current simulation.

Subcellular modeling of thin slots in the finite-difference time-domain (FDTD) method is investigated. Two sub-cellular algorithms for modeling thin slots with the FDTD method are compared for application to shielding enclosures in electromagnetic compatibility (EMC). The stability of the algorithms is investigated, and comparisons between the two methods for slots in planes, and slots in loaded cavities are made. Results for scattering from a finite-length slot in an infinite plane employing one of the algorithms are shown to agree well with published experimental results, and power delivered to an enclosure with a slot agree well with results measured for this study. Index Terms - FDTD, slot.

An extended point-matching method for analyzing the shielded microstrip transmission lines with thick electrodes has been developed based on [1]. This method provides a simple and fast approach to the quasi-static analysis of the structures. The calculated fields are used to estimate the characteristic impedance and effective dielectric constant of the structures. The results agree well with available theoretical results obtained using other methods, such as the finite element method and the boundary element method. This method can be further applied to other microstrip lines widely used in monolithic microwave integrated circuits (MMIC's) applications. Index Terms - Point-matching method, shielded microstrip lines.

A methodology for accurate calculations of shielding factors for quasistatic multilayered magnetic shields is described. 'Transfer relations' for individual layers with specified magnetic permeabilities and electrical conductivities are spliced together in a manner that is analogous to splicing impedances for cascaded sections of transmission line. Specific transfer relations for four layer geometries (planar, cylindrical with transverse fields, cylindrical with axial fields, and spherical) and constraints at source and shielded surfaces for six source-shield configurations involving both externally applied fields and enclosed sources are developed. Limiting cases are extracted for magnetically permeable, nonconducting layers, and for thin, magnetically nonpermeable, conducting layers. Reciprocity conditions are identified for interchanged source and shielded regions in planar, transverse field cylindrical, and spherical geometries. Variations of magnetic field and flux density with position are shown for a specific planar example involving alternating layers of aluminum and steel, with the same total shield thickness occupied by either one or five layer pairs. Simulations with alternating layers of aluminum and steel for the four layer geometries are used to answer questions regarding the effects of material composition, number of layer pairs, and air gaps. An optimal number of layer pairs for a given total shield thickness is identified. Results from simulations where induced currents in the steel layers are neglected are compared with those for simulations with a realistic conductivity value for steel to assess the relative effects of flux shunting and induced current shielding. The effects of introducing air gaps between material layers upon overall shielding factor magnitude are shown.

The detection of stealth point targets has presented serious challenges to the design of conventional radars using sinusoidal carriers since the objective of the stealth technology has been to reduce the radar cross section (RCS) of targets to a level where the radar receiver cannot detect the target. While there are a number of techniques employing different technologies to reduce the RCS of targets, shaping and coating the target with absorbing material are the most useful ones. The analysis and design of nonsinusoidal radar signals is based on modeling stealth point targets by a two-layer structure consisting of a metal surface covered with a coat of absorbing material. The design is presented for two classes of signals: uncoded signals and pulse compression signals using Barker codes. The relationship between target response, absorbing material time delay, time variation of transmitted pulses and coding features are determined and analyzed. While sliding correlators are used for detection and selection of various target responses, their output auto-correlation functions are determined analytically in terms of transmitted signal autocorrelation functions. Thumbtack range-velocity resolution functions are obtained for transmitted signal characters with a single pulse and characters with coded waveforms, for different pulse duration. It is shown that the range resolution can be improved by the proper choice of the transmitted signal duration relative to absorbing material time delay. Thumbtack range-velocity resolution functions similar to those of conventional point targets can also be realized.

The scattering of a diaphragm in a packaged microstrip line is investigated using the mode-matching method together with the method of lines. Instead of analyzing the discontinuity in the microstrip, this paper tackles the variation of the waveguide housing. The influences of the thickness and the depth of the diaphragm on the scatterings of the dominant mode and higher-order modes are analyzed based on a comparison of the modal power distributions. Finally, the shielding effect of a pair of closely spaced diaphragms is investigated.

The Concentric MESFET (CMESFET) is a small-signal, traveling-wave transistor in which a grounded source electrode surrounds and shields the gate and drain electrodes from electromagnetic fields generated by other nearby circuit elements. S-parameters for the transistor are computed to obtain gain curves fo several design configurations. For a gate length of 2 [[micro]meter], maximum gain occurs with a gate width of 3.0 mm. The CMESFET has a calculated bandwidth of 17 GHz for this gate length and a gate width of 300 [[micro]meter]. Coupling capacitances between device electrodes and a nearby transmission line are calculated to demonstrate how the shielding source electrode isolates the devic from interference and crosstalk originating in the surrounding circuit. The CMESFET geometry exhibits shielding characteristics better than those of conventional small-signal FET geometries.

The method of lines (MoL) is applied to the analysis of shielded microstrip lines with bi-anisotropic biaxial substrates and superstrates (cover layers). Two coupled differential equations for the tangential electric field components which govern the field behavior within anisotropic region, are derived using differential matrix operators. The MoL procedure is employed to discretize abov equations along the transverse direction of the transmission line. Numerical results emphasize effects of strip-width, thickness of the substrate, and thickness of the superstrate on propagation characteristics of the line. In addition, the propagation constants of higher order modes are calculated for frequencies ranging from 1 to 35 GHz for substrates also exhibiting magnetic anisotropy. It is found that for this structure higher order modes tend to exis in clustered pairs.

A shielded sub-mm/THz monolithic transition between a layered dielectric waveguide and a strip-ridge line is characterized using two different approaches: the integral equation-mode matching (IEMM) method and the finite difference time domain (FDTD) technique. While higher order modes are considered, a simple method for determining the transition's circuit model (i.e., two-port scattering matrix) from the IEMM results is implemented and the electrical performance is studied as frequency and conductor width are varied. The FDTD analysis gives further insight into the behavior of the transition in a very wide frequency range (0-540 GHz). The transition is found to be very efficient over a wide frequency band and a broad range of conductor widths.

In this paper, we discuss the shielding characteristics of an inhomogeneous shield for oblique incidence. The inhomogeneity here considered can be modeled via a continuous spatial variation of the permittivity along the power-flow direction and can be taken into account in the mathematical model involving the transmission line equivalent-circuit representation in terms of a longitudinal-line impedance and a transverse-line admittance varying along the same direction. In order to design a filter or a matching line layout with such a material, new analytical expressions of the reflection coefficient and of the shielding factor for nonuniform dielectric slabs are found. Some numerical examples are also presented for both the TE and TM polarization cases. Index Terms--Distributed parameter circuits, filters, shielding.