C. Christopoulos

A fully integrated multiconductor model for TLM

A fully integrated model of coupling between the electromagnetic field and multiconductor cabling is developed using the transmission line matrix (TLM) method. In this model, the multiconductor cables are represented by multiconductor transmission lines which connect to the general TLM mesh.

Decoupled simulation of DC-linked power electronic systems using transmission-line links

This paper describes the application of the transmission-line modeling (TLM) method to the decoupled simulation of DC linked power electronic systems. Stiff capacitively or inductively smoothed DC links in power electronic systems can be modeled as two-port transmission-line links using the TLM method. The TLM links enable the circuits connected by the links to be decoupled and simulated as individual circuits, resulting in smaller system matrices, possibility of parallel computation and reduction in computing time. Interaction between these linked circuits can be realised by exchanging the incident pulses at both ends of the transmission-line links. Computer simulations of an AC to DC converter used in a laboratory confirms the simplicity of the TLM decoupled simulation approach. >

The use of Unscented Transforms for statistical analysis in EMC

The use of unscented transforms UT for the statistical analysis of nonlinear linear problems is described. The UT methodology is then applied to the analysis of wire coupling within an enclosure which is a typical problem encountered in EMC studies. The UT results are compared with the more traditional Monte Carlo approach. It is demonstrated that UT is a powerful technique that can greatly improve the computation of the uncertainty encountered in many EMC studies.

Effect of logic family on radiated emissions from digital circuits

Radiated emissions were measured for simple digital circuits designed to operate with various logic families. Emissions in the near and far field were found to depend both on the circuit layout and the choice of logic family. However, the difference in peak emissions between any two logic families was found to be independent of the circuit layout. The greatest difference in peak emissions was between high-speed 74ACT logic and low-speed 4000 CMOS logic devices, with a mean value of approximately 20 dB. Emissions from a more complex circuit were compared with the measurements on simple loop circuits. Test circuits were used to measure the propagation delay, the rise and fall times, the maximum operating frequency and the transient switching currents between two successive logic gates for each logic family. Empirical formulas have been derived that relate relative peak emissions to these switching parameters. It is hoped that these will assist designers to assess the effect of choice of logic family on electromagnetic compatibility.

Analytical and experimental study of the shielding effectiveness of a metallic enclosure with off-centered apertures

An analytical formulation has been developed for the shielding effectiveness of a rectangular enclosure with off-centered apertures. The present analytical formulation has been extended to include modes higher than TE10. The electric shielding may be calculated as a function of frequency, enclosure dimensions, aperture dimensions and position within the enclosure. Measurements conducted in a Gigahertz transverse electromagnetic (GTEM) cell show good agreement with theoretical values

The opportunities and challenges associated with wireless interconnects in aircraft

Abstract Utilizing wireless data buses in aircraft has the potential to increase reliability, reduce weight, and improve flexibility and adaptability. In this article, the implementation of wirelessly connected interconnects in aircraft is introduced from a broad perspective, considering the issues of radio systems, propagation, antennas, and applications. Existing avionics systems are discussed briefly in order to understand the requirements placed on a wireless system and the specification it must meet. A review of existing wireless protocols and commercial off the shelf systems is provided, explaining where systems including ZigBee and IEEE 802.11 are suitable and unsuitable for a wireless aircraft application, and it is found that no existing system can be used exclusively. It is shown quantitatively that the propagation environment is expected to have high delay spreads and the negative impact of this on system reliability is shown through simulation and measurements. The application and benefits of a direct write, in-situ, metallic deposition procedure are discussed for the placement of antennas, sensors, and their associated electronics. By writing electronics onto a surface, fitting and retrofitting are made much easier without the need to affect the aircraft structure, and this enables a more flexible wireless system. The opportunities, advantages and challenges for such a technology within the wireless aircraft are discussed.

Comparison of simulated and recorded transients for travelling wave fault location

In order to assist in the location of EHV transmission line faults using travelling wave transients a program has been devised where the transients are simulated and compared with those recorded. The simulation scheme is based on the well-known ATP program, which has been found to be satisfactory for sample step times of 800 ns. The fault transients have been recorded at a 800 ns sample rate via a current probe attached to the secondary circuit of the current transformers. An offline analysis program has been written in Matlab/spl trade/ which then converts the simulated transients into a form that allows direct comparison with the recorded transients and also provides extra analysis routines. This greatly improves the confidence in a given fault location estimate. Example faults recorded on the ScottishPower EHV transmission system are given which demonstrate the utility of this scheme.

A genetic algorithm based method for modeling equivalent emission sources of printed circuits from near-field measurements

A method for modeling electromagnetic emissions from printed circuits with equivalent dipole sources is presented. An optimization procedure based on the genetic algorithm is used to determine the number of equivalent dipoles and their parameters by fitting to the measured near fields. Prediction of emissions from the PCB can then be obtained by computing from the equivalent model without reference to the details of the PCB.

Electromagnetic coupling to an enclosure via a wire penetration

This paper presents an efficient model, which can be computed in seconds, for the coupling of external electromagnetic fields to the contents of an enclosure via wire penetrations. The coupling path accounts for the coupling of an external electric field to a wire penetration that establishes an internal electric field via the connect and internal wire segment. The internal electric field then couples onto another victim wire segment, inside the box. The accuracy of the model is demonstrated by the good agreement obtained between predicted induced voltage on the victim wire segment, and experimental measurements.

Experimental verification of predicted electromagnetic fields radiated by straight interconnect cables carrying high-frequency currents

This paper provides an experimental verification of analytical expressions for predicting radiated electromagnetic fields from straight interconnect cables carrying high-frequency currents. These analytical expressions are derived through two different models. The former model is based on the assumption that a radiating two-wire transmission line can be considered as two Hertzian dipoles, while in the latter one each radiating wire is treated as a chain of short radiating dipoles. The radiated field is calculated and measured at selected locations and the results are compared in order to verify the agreement among them. Different configurations (two parallel cables at various distances from a conducting ground plane) are considered.