Electromagnetic Compatibility Applications Research Articles

An explicit weighted essentially nonoscillatory time-domain algorithm for 3-D EMC applications with arbitrary media interfaces

The precise modeling of arbitrarily aligned different material interfaces in composite electromagnetic compatibility (EMC) applications, is introduced in this paper through a fully explicit family of three-dimensional weighted essentially nonoscillatory schemes in the time domain. Developing curvilinear tessellations of auxiliary nodes compliant with a convex combination of all optimal candidate stencils, the novel algorithm allocates pertinent weights for wide-band evaluations at the particular regions. Also, via an enhanced temporal integration, continuity conditions are imposed in a local regime, without any unfavorable instabilities or vector parasites. Thus, the prior volumetric concepts suppress intrinsic grid defects even when time-steps are fairly large unlike in usual approaches. Numerical analysis verifies these benefits by diverse realistic EMC structures with laborious interfaces of complex shapes, curvatures, and dissimilar media configurations

A Generalized Node for Embedding Subwavelength Objects Into 3-D Transmission-Line Models

The transmission-line modeling (TLM) method is a well-established time-domain numerical algorithm for electromagnetic simulation and has been employed in a wide range of application areas. Producing accurate simulations of problems involving both physically important fine features, such as thin wires, as well as large-scale objects has proved very demanding, both in terms of computer time and memory. Clearly, such problems occur in many electromagnetic compatibility (EMC) applications. A general TLM node has been derived from rigorous field analysis that allows the embedding of almost arbitrarily shaped small objects within TLM cells. In particular, this approach allows the highly important case of short lengths of thin wires which are obliquely orientated to the cell faces to be tackled efficiently and, consequently, piece-wise linear models of arbitrarily routed curved wires to be modeled.

Transient Reflection Properties of a Dispersive and Lossy Bi-Isotropic Slab With an Anisotropic Laminated Composite Backing

This paper presents a detailed analysis of the transient reflection from a general bi-isotropic slab backed by a laminated composite. Either a nonreciprocally Tellegen medium or a reciprocally dispersive chiral medium with losses is considered as the bi-isotropic slab. The laminated composite is a graphite-fiber-reinforced-plastic composite (GFRPC), which has been widely used as a replacement for metals and may be treated as a multilayered anisotropic medium from the electromagnetic point of view. For the analysis, a theoretical model is developed based on a state-equation approach. On the basis of this model, both the time-domain and the frequency-domain plane-wave reflection results are obtained and studied. The factors affecting the results, such as the material parameters of the bi-isotropic slab and the fiber-orientation pattern of the GFRPC, are investigated in detail. Some special reflection properties, such as the twist-polarizer reflection and the antireflection, are observed based on this investigation. The properties may lead to a novel transient absorber technology for electromagnetic compatibility (EMC) applications.

A New Test Setup and Method for the Calibration of Current Clamps

Current probes are widely used to measure the common mode currents in electromagnetic compatibility (EMC) applications. Often, it is necessary to characterize the ratio of measured voltage to the common mode currents up to gigahertz (GHz) frequencies. Existing calibration methods for current probes suffer from the problem of not directly measuring the current within the current clamp. Instead they either reconstruct the current from measurements at other locations or they use assumptions regarding the geometry which allows them to use a current that is measured at a different location without applying a mathematical correction. For example, by maintaining a 50-/spl Omega/ transmission-line impedance the current can be determined with low uncertainty. The proposed method overcomes these disadvantages by directly measuring the current at the center of the current clamp. This way the mechanical dimensions of the test setup are not critical any more, i.e., one setup can be easily used to measure a large variety of clamps. The method is primarily applicable for current monitoring probes in the frequency domain.

An Unconditionally Stable Higher Order ADI-FDTD Technique for the Dispersionless Analysis of Generalized 3-D EMC Structures

An efficient higher order alternating-direction implicit (ADI) finite-difference time-domain (FDTD) method for the unconditionally stable analysis of curvilinear electromagnetic compatibility (EMC) applications is presented in this paper. The novel algorithm launches a class of precise spatial/temporal nonstandard forms that drastically suppress the dispersion errors of the ordinary approach as time-step increases and mitigate its strong dependence on cell shape or mesh resolution. For arbitrary interface media distributions that do not follow the grid lines, a convergent transformation based on a rigorous extrapolating practice is introduced. Moreover, infinite domains are successfully treated by optimized higher order curvilinear PMLs. Hence, the proposed technique achieves notable accuracy far beyond the Courant limit, subdues the ADI error mechanisms, and offers serious savings, as verified by the solution of several complex EMC problems.

A Higher Order Nonstandard FDTD-PML Method for the Advanced Modeling of Complex EMC Problems in Generalized 3-D Curvilinear Coordinates

A higher order finite-difference time-domain perfectly matched layer (PML) methodology for the systematic modeling of generalized three-dimensional electromagnetic compatibility (EMC) problems, is presented in this paper. Establishing a covariant/contravariant formulation, the novel algorithm introduces a parametric topology of accurate nonstandard schemes for the nonorthogonal div-curl problem and the suppression of lattice dispersion. Also, the wider boundary stencils are treated by compact operators, while a mesh expanding process reduces the absorber's depth. At arbitrarily-aligned interfaces, consistency is preserved through a convergent concept that considers the proper continuity conditions. Hence, the enhanced PMLs attain large annihilation rates for complex domains and broadband spectrums. Numerical validation-stressing on evanescent waves near scatterers-confirms the superiority of the proposed algorithm via realistic EMC applications, like shielding enclosures, printed circuit boards, and modern antennas.

Analysis of aperture coupling of electromagnetic energy in cylindrical wall [EMC applications

The coupling of electromagnetic (EM) waves through an aperture in a cylindrical wall is analyzed by the method of moments (MoM), in conjunction with the free-space dyadic Green function. A transmission coefficient of the aperture is defined and calculated. The result provides useful physical insight in electromagnetic compatibility (EMC) issues of sophisticated electronic systems.

Wide-band characterization of current probes

The use of current probes for the injection of wide-band disturbance in electromagnetic compatibility applications requires their accurate characterization up to few gigahertz. While the representation of the current probe with a simple transformer is acceptable at low frequencies, the spectral content of fast signals requires models which are accurate even at gigahertz frequencies. This can be accomplished directly by measurements in the frequency domain (FD), making use of a S-matrix representation of the probe, or in the time domain (TD), recovering the transfer functions from the impulse responses measurement. Both techniques suffer limitations due to numerical and experimental problems; in particular, the FD approach leads to the solution of an inverse problem, with numerical instabilities in the high-frequency range, whereas the TD approach is not so accurate in the low-frequency range of the sought transfer function. The paper combines the two techniques to overcome these difficulties and achieve a better accuracy across the overall bandwidth. The characterization of a commercially available current probe allows comparison of numerical results with experimental measurements.

A subgridding scheme based on mesh nesting for the FDTD method

A new and stable subgridding scheme based on mesh nesting is presented. This scheme is numerically stable, accurate, and easy to implement. The accuracy of the scheme is illustrated by examples of applications in electromagnetic compatibility (EMC). ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 211–214, 1999.

Spherical near-field facility for microwave coupling assessments in the 100 MHz-6 GHz frequency range

This paper describes a spherical near-field facility set up at the Centre d'Etudes de Gramat (CEG) to perform low-power microwave coupling assessments. Specifically, this facility has been designed to determine the coupling cross section of a complex object. However, it can also be used for the characterization of any radiating system in electromagnetic compatibility (EMC) or high-power microwave (HPM) environments. The near-field approach is shown to be complementary and to offer increased flexibility when compared to other more conventional measurement techniques. More particularly, the use of a probe array in the upper part of the frequency band significantly speeds up the near-field measurement process. Consequently, broadband and multiparameter acquisitions can be performed within acceptable duration. The examples given in this paper provide a broad illustration of the capabilities of near-field techniques for EMC and HPM applications.

The design of dipole and monopole antennas with low uncertainties

Close agreement between the measured and predicted insertion loss between dipole antennas above a conducting ground plane has produced a calculable standard dipole antenna. Antenna factors of dipole antennas in the frequency range 30 MHz to 500 MHz have been determined to an uncertainty of /spl plusmn/0.1 dB. Though the design of the dipole is not new, the key achievements are: the use of a large standard ground plane, the use of the program NEC to obtain broadband results, careful design of antennas and supports and precision measurements. Insertion loss and antenna factor are calculated by two independent methods, numerical and analytical, and the results agree to better than /spl plusmn/0.05 dB. The NPL calculable dipole antenna was originally designed for electromagnetic compatibility (EMC) applications in the frequency range 30 MHz to 1 GHz, but it can be used wherever electric field strength of free-field signals needs to be precisely measured. The technique was applied to monopole antennas for which antenna factor was determined to an uncertainty of /spl plusmn/0.15 dB over the frequency range 10 MHz to 100 MHz. In this paper, traceability of antenna factor to the predicted value rather than a measured value is justified.

Extension of method of moments for electrically large structures based on parallel computations

An integral equation formulation in conjunction with a novel parallel method of moments (PMoM) is proposed to analyze the response of electrically large structures, consisting of conducting or dielectric parts, to a time harmonic excitation. The inherent parallelism of the introduced technique allows for the results to be obtained with minimal addition to the sequential code programming effort. Two indicative electromagnetic compatibility applications are presented, while the applicability/suitability of diverse high performance computing (HPC) platforms is judged, based on both performance obtained and ease of code portation.