Search

The paper focuses on the reverberation chamber method for the shielding properties evaluation of equipment-level enclosures. The enclosure under test is numerically modeled by an in-house finite-difference time-domain code that is able to predict the field inside the enclosure and the voltage captured by the probe placed inside it. The chamber fields have been modeled by applying the plane-wave superposition. The code is validated by measurements in our reverberation chamber. Subsequently, the effect of probe positioning and length on the induced voltage is analyzed. Finally, the enclosure shielding effectiveness is evaluated by applying two different definitions, and a statistical analysis is carried out, thus allowing an estimation of the measurement uncertainty. Index Terms--Finite-difference time domain (FDTD), frequency stirring, plane-wave superposition, reverberation chamber, shielding effectiveness, small enclosures.

In this paper, a self-consistent model is developed of the propagation of an electromagnetic wave into a plasma region, based on the solution of the Maxwell-Boltzmann system of equations. The system is resolved using a finite-difference time-domain approach that gives as results the behavior of both the particle velocity distribution function and the electromagnetic fields. The method is applied to a simple situation in which a wave impinges on a plasma region, but can easily be extended to more complicated configurations. Index Terms--Boltzmann equation, electron distribution function, finite-difference time-domain (FDTD), plasma.

The paper considers the reverberation chamber (RC) method for the measurement of the shielding effectiveness (SE) of coaxial cables with braided shields. In particular, the voltage at the cable termination is numerically computed and compared to that measured in an RC. The RC field is represented by a finite summation of random plane waves, and a finite-difference time-domain (FDTD) code is used to calculate the outer shield current induced by the RC field. The knowledge of the shield current distribution allows the determination of the voltage at the cable termination's internal circuit after a proper numerical averaging. It is then compared to the measured voltage averaged over stirrer rotations. The method is applied to a commercially available cable model RG58, and using the nominal value for the transfer impedance of this cable type gives results in a satisfactory agreement with the measurements. Finally, the possibility of recovering the transfer impedance from the measured SE of the RC is discussed. Index Terms--Finite-difference time-domain (FDTD) methods, reverberation chamber (RC), shielding effectiveness (SE), transfer impedance.

This paper presents how it is possible to characterize a current probe in terms of its transfer impedance inside a reverberation chamber. The probe catches a floating wire placed inside the working volume of the chamber. The current on the wire is calculated from the knowledge of the total measured average field along the wire in the working volume. The current is calculated by representing the field in terms of a summation of random plane waves, where a finite-difference time-domain (FDTD) code is used to compute the current induced by each plane wave along the wire caught by the probe under test. Results for the current distribution along the wire are reported for several frequencies. Finally, the transfer impedance of commercial probes is recovered from the knowledge of the current and compared to the values given by the manufacturers and by an external laboratory. Index Terms--Current probe calibration, FDTD methods, reverberation chambers, transfer impedance.

The aim of the present work is to investigate pacemaker (PMK) immunity against high-level extremely low frequency (typically 50 Hz) magnetic fields that can be found in industrial environment where high power machines operate. To that purpose, a test bench has been set up using a Helmholtz coil for producing extremely low frequency magnetic fields and a trunk simulator rightly fed by cardiac signals. A widely used PMK was tested, and results have been reported, under different operating conditions, for both continuous waves and variously pulsed excitations. A numerical tool has also been developed to analyze the realized test bench, based on a proper discretization of a human trunk simulation and on the construction of an equivalent three-dimensional (3-D) network. Numerical results have showed a good agreement with the experimental results. Index Terms--ELF fields, Helmholtz coil, immunity tests, pacemaker (PMK).

This paper presents a study of coupling between an external field and a metallic enclosure with a long aperture in the frequency range which includes several box resonances. A reverberation chamber (RC) and an anechoic chamber (AC) are considered as a field generation structure. In both cases, a customized FDTD code is used to calculate the current induced by the external field in a loop placed inside the enclosure. In order to simulate the AC facility, a single plane wave is used to represent the test field, whereas for the RC, the field is represented by a proper superposition of random plane waves. Numerical results are experimentally validated. The proposed method is useful to investigate the performance of the enclosure during its early design stage before the realization of a prototype. Index Terms--Anechoic chambers (AC), FDTD methods, immunity, reverberation chambers (RC).

The behavior of a device in a reverberation chamber can be analyzed as the same device irradiated by random plane waves. This work proposes an application of the finite difference time domain method to analyze the device by using a superposition of random plane waves, simulating the behavior of a reverberation chamber. The analysis of a transmission line compared with theoretical and experimental results in a reverberation chamber is reported. Index Terms--Finite difference time domain (FDTD) methods, random plane wave generation, reverberation chambers, superposition of plane waves.

Over recent years, reverberation chambers have been analyzed by many numerical techniques. This contribution studies how the finite-difference time-domain algorithm converges to the steady state conditions as a function of the cavity Q factor, changing the wall conductivity or the internal lossy media. By lowering the reflection coefficient of the chamber walls, the computation time could be considerably reduced without a significant effect on the field distribution for any analyzed antennas. The field distributions are strongly correlated when the conductivity of the wall is one hundredth of the copper conductivity or greater, whereas when the conductivity is lower the correlation between field distributions is low. Index Terms--Finite-difference time-domain (FDTD), finite wall conductivity, numerical convergence, reverberation chambers, time constant.

Finite Difference-Time Domain (FDTD) methods offer, in principle, promise of great flexibility for application to waveguide discontinuities of any kind. The problem of appropriate termination in the guide environment has recently been addressed. Main remaining disadvantages are the volume of computation involved and lack of analytical insight. Moreover equivalent circuits are prerequisites to effective CAD and synthesis. With a view to remedying these shortcomings, we discuss the extraction from the FDTD analysis of equivalent circuits. Two significant examples are considered: the inductive post and the 90 [degrees] H-plane corner, including a modified form of the same. The circuits thus obtained are subsequently employed in the CAD problem of matching over the full waveguide band the modified corner by means of two inductive screws. Theoretical and experimental results are in excellent agreement yielding a reflection [less than or equal to] -12 dB over the band 36-40 GHz and showing the effectiveness of the approach.

In recent years, various techniques have been developed for the study of microwave mixers. The present contribution stems from the method introduced in [1] for the nonlinear analysis, but differs in the linear part. In particular, we emphatize the circuit characterization of the mixer harmonics, removing the usual approximation of matched terminations and employing models that effectively represent network characteristics in the microwave and millimeter wave domain. This goal is achieved through the accurate knowledge of the various components occurring in the mixer and the use of accurate equivalent circuits. In order to validate the model, two subharmonic mixers operating at K-band (18-26 GHz) were realized. Reasonable agreement is achieved between theoretical and experimental results.

Recent research on computer aided design (CAD) of rectangular waveguide elements is presented. It reports on a novel broadband equivalent circuit model of inductive posts in waveguide filters for precise CAD synthesis of such filters. The model, which was developed on a personal computer, considers only the post configuration and hasthe ability to characterize higher mode interactions also.

We analyzed how the position of the stirrer influences the reverberation chamber (RC) performance. We simulated a RC moving the rotation axis of the stirrer from a corner to the center. Simulation is carried out by a finite-difference time-domain code optimized for high-performance computers. Results show that the stirrer rotation center position weakly affects the most used statistical parameters. [ABSTRACT FROM PUBLISHER]

This paper analyzes the performance of a reverberation chamber when the working volume (WV) is positioned inside the stirrer rotating volume. More precisely, considering a very large stirrer, its inner surface and axis are removed to gain a large space to be used as WV. The design of this new WV position and stirrer shape is done using our finite-difference time domain code, previously optimized for reverberation chamber simulations and tested with experimental results. The proposed setup increases the WV and improves the reverberation chamber behavior with respect to a traditional setup. Moreover, it needs just one motor to control the stirrer, and it does not require more complex mechanical part. [ABSTRACT FROM AUTHOR]