56 research outputs found
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
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Glass Furnace Combustion and Melting Research Facility.
The need for a Combustion and Melting Research Facility focused on the solution of glass manufacturing problems common to all segments of the glass industry was given high priority in the earliest version of the Glass Industry Technology Roadmap (Eisenhauer et al., 1997). Visteon Glass Systems and, later, PPG Industries proposed to meet this requirement, in partnership with the DOE/OIT Glass Program and Sandia National Laboratories, by designing and building a research furnace equipped with state-of-the-art diagnostics in the DOE Combustion Research Facility located at the Sandia site in Livermore, CA. Input on the configuration and objectives of the facility was sought from the entire industry by a variety of routes: (1) through a survey distributed to industry leaders by GMIC, (2) by conducting an open workshop following the OIT Glass Industry Project Review in September 1999, (3) from discussions with numerous glass engineers, scientists, and executives, and (4) during visits to glass manufacturing plants and research centers. The recommendations from industry were that the melting tank be made large enough to reproduce the essential processes and features of industrial furnaces yet flexible enough to be operated in as many as possible of the configurations found in industry as well as in ways never before attempted in practice. Realization of these objectives, while still providing access to the glass bath and combustion space for optical diagnostics and measurements using conventional probes, was the principal challenge in the development of the tank furnace design. The present report describes a facility having the requirements identified as important by members of the glass industry and equipped to do the work that the industry recommended should be the focus of research. The intent is that the laboratory would be available to U.S. glass manufacturers for collaboration with Sandia scientists and engineers on both precompetitive basic research and the solution of proprietary glass production problems. As a consequence of the substantial increase in scale and scope of the initial furnace concept in response to industry recommendations, constraints on funding of industrial programs by DOE, and reorientation of the Department's priorities, the OIT Glass Program is unable to provide the support for construction of such a facility. However, it is the present investigators' hope that a group of industry partners will emerge to carry the project forward, taking advantage of the detailed furnace design presented in this report. The engineering, including complete construction drawings, bill of materials, and equipment specifications, is complete. The project is ready to begin construction as soon as the quotations are updated. The design of the research melter closely follows the most advanced industrial practice, firing by natural gas with oxygen. The melting area is 13 ft x 6 ft, with a glass depth of 3 ft and an average height in the combustion space of 3 ft. The maximum pull rate is 25 tons/day, ranging from 100% batch to 100% cullet, continuously fed, with variable batch composition, particle size distribution, and raft configuration. The tank is equipped with bubblers to control glass circulation. The furnace can be fired in three modes: (1) using a single large burner mounted on the front wall, (2) by six burners in a staggered/opposed arrangement, three in each breast wall, and (3) by down-fired burners mounted in the crown in any combination with the front wall or breast-wall-mounted burners. Horizontal slots are provided between the tank blocks and tuck stones and between the breast wall and skewback blocks, running the entire length of the furnace on both sides, to permit access to the combustion space and the surface of the glass for optical measurements and sampling probes. Vertical slots in the breast walls provide additional access for measurements and sampling. The furnace and tank are to be fully instrumented with standard measuring equipment, such as flow meters, thermocouples, continuous gas composition analyzers, optical pyrometers, and a video camera. The output from the instruments is to be continuously recorded and simultaneously made available to other researchers via the Internet. A unique aspect of the research facility would be its access to the expertise in optical measurements in flames and high temperature reacting flows residing in the Sandia Combustion Research Facility. Development of new techniques for monitoring and control of glass melting would be a major focus of the work. The lab would be equipped with conventional and laser light sources and detectors for optical measurements of gas temperature, velocity, and gaseous species and, using new techniques to be developed in the Research Facility itself, glass temperature and glass composition
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