Uncertainty Analyses in the Finite-Difference Time-Domain Method

Providing estimates of the uncertainty in results obtained by Computational Electromagnetic (CEM) simulations is essential when determining the acceptability of the results. The Monte Carlo method (MCM) has been previously used to quantify the uncertainty in CEM simulations. Other computationally efficient methods have been investigated more recently, such as the polynomial chaos method (PCM) and the method of moments (MoM). This paper introduces a novel implementation of the PCM and the MoM into the finite-difference time -domain method. The PCM and the MoM are found to be computationally more efficient than the MCM, but can provide poorer estimates of the uncertainty in resonant electromagnetic compatibility data

A simple model of EMI-induced timing jitter in digital circuits, its statistical distribution and its effect on circuit performance

A simple model has been developed to characterize electromagnetic interference induced timing variations (jitter) in digital circuits. The model is based on measurable switching parameters of logic gates, and requires no knowledge of the internal workings of a device. It correctly predicts not only the dependence of jitter on the amplitude, modulation depth and frequency of the interfering signal, but also its statistical distribution. The model has been used to calculate the immunity level and bit error rate of a synchronous digital circuit subjected to radio frequency interference, and to compare the electromagnetic compatibility performance of fast and slow logic devices in such a circuit

Reduction of radiated emissions from apertures in resonant enclosures by the use absorptive materials

Preliminary results are presented which show that the radiation from non-resonant (i.e. electrically small) apertures in metallic enclosures is enhanced at the closure resonances. It is shown that the levels of radiation at resonance can be significantly reduced by the use of ferrite absorbing tiles or carbon loaded dielectric absorbers to damp the enclosure resonances. A simple equivalent circuit model has been developed which allows prediction of the effects of absorber and slot placement for first order waveguide modes. It is believed that the model can be extended to higher order mode

A wide-band hybrid antenna for use in reverberation chambers

This paper describes the design and performance of a wide-band hybrid antenna suitable for use in reverberation chambers. The antenna is characterised over the frequency range 100 MHz to 25 GHz showing that it performs well above 200 MHz although its ultimate highest operating frequency has not been established

Electromagnetic Monitoring of Semiconductor Ageing

AbstractThis paper reports on the outcomes of the project “Electromagnetic Monitoring of Semiconductor Ageing” funded through the EPSRC Centre for Innovative Manufacturing in Through-life Engineering Services. The basis of the feasibility study reported in this paper is that all active devices exhibit non-linear behaviour and the behaviour of those devices will change as they age. As a result, the radiation or re-radiation of intermodulation products will change as the device ages. The goal of the project is to verify that this change in non-linear behaviour could be identified in a way that does not require modification of existing circuitry, thus allowing through-life and non-destructive monitoring of devices for signs of early deterioration. Results obtained from this work have been very encouraging and have set the scene for further development of the techniques to include degradation fingerprinting and system health monitoring

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 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

Electromagnetic coupling to an enclosure via a wire penetration

Abstract: The paper presents results which demonstrate that radiated emissions from heatsinks are reduced by an amount that depends upon the distribution and impedance of the grounding structure. Results are also presented which show the effect on radiated emissions of the presence of conductors (e.g. PCB tracks) passing under the heatsink. The presence of conductors reduces the effectiveness of the heatsink grounding but, in most case, emissions at high frequencies do not exceed those without conductors attached