Staircasing of surfaces is a known and well documented source of error in FDTD models on orthogon... more Staircasing of surfaces is a known and well documented source of error in FDTD models on orthogonal structured meshes; however, very little work focuses on such errors in simulations of electromagnetic cavities. This work examines the different errors that arise as a direct result of using an orthogonal approximation of a hollow spherical shell. The spherical shell used has a radius of 1 m and is constructed of a simple material with a conductivity σ = 1000 S/m and a thickness h = 1 mm. This material was represented using a thin boundary SIBC model allowing a mesh size much larger than the thickness of the material. The orthogonally meshed sphere was illuminated using a planewave and the electric field measured at the centre allowing the shielding effectiveness (SE) to be calculated.
The averaged absorption cross section (ACS) of a lossy object characterises its ability to captur... more The averaged absorption cross section (ACS) of a lossy object characterises its ability to capture power from diffused electromagnetic waves. The averaged ACS is very important in many EMC research areas such as indoor wireless channel modelling and human safety exposure study. The measurement of averaged ACS in a reverberation chamber can be achieved by measuring the rate of power loss in the time domain, however this technique requires dense frequency sampling for taking the inverse Fourier transform, which is very time consuming. A new scenario which accelerates the measurement speed is presented in this paper. It combines the technique of non-linear curve fitting to the power delay profile, segmented frequency sweeping and continuous mode stirring. The scenario was validated by measuring the averaged ACS of a hollow plastic sphere filled with deionized water in an EMC reverberation chamber. Measurement results showed a good accordance with the simulations and the measurement unc...
The indirect two-port reflection method for measuring antenna impedances is reviewed using scatte... more The indirect two-port reflection method for measuring antenna impedances is reviewed using scattering parameter techniques and developed into a more accurate low perturbation optically coupled transmission measurement. This transmission measurement infers the antenna impedance by measuring the voltage induced in a number of loads connected to the antenna port with reference to the antenna used for illumination. Both these techniques have proved to be very versatile: applications to a typically electromagnetic compatibility problem, consisting of a box and wire above a ground plane, and to the design of a challenging multi-band Digital Audio Broadcast antenna are presented. INTRODUCTION In this paper we propose to present our latest results to illustrate the flexibility of the technique. The first application is a classical box-wire-box system, where the radiation impedance is solved by measuring the reflection coefficient from the probe antenna. The second application is an antenna ...
A new broad-band antenna structure specifically designed for antenna position stirring in a rever... more A new broad-band antenna structure specifically designed for antenna position stirring in a reverberation chamber is described. The antenna features a reactive rotating source coupler that overcomes the problems of cable and connector reliability and stability often encountered in antenna source stirring due to cable movement. The stirring performance of the new antenna is evaluated by observation of the reduction in Rician K-factor facilitated by the antenna.
2017 International Conference on Electromagnetics in Advanced Applications (ICEAA), Sep 1, 2017
Diffusion equation based modeling has been proposed for mapping the reverberant component of th... more Diffusion equation based modeling has been proposed for mapping the reverberant component of the electromagnetic field in enclosures at high frequencies. Preliminary evaluation of the electromagnetic diffusion model using a dimensional reduction approach showed promising results compared to measurements. Here we develop a full three-dimensional diffusion model of the experimental canonical test cases considered in the preliminary evaluation and obtain finite element method solutions. The results are compared to those of the two-dimensional models. We find that the two-and three-dimensional models are generally in excellent agreement for the pseudo two-dimensional test-cases considered. Some deviations between the two-and threedimensional models are observed due to the fact the point source must be effectively represented by a line source in the reduced model. The three-dimensional model is still highly efficient compared to other applicable techniques, offering the prospect of a radical reduction in the resources required for simulating reverberant fields in electrically large structures.
IEEE Transactions on Microwave Theory and Techniques
Thin sheet models are essential to allow shielding effectiveness of composite enclosures and vehi... more Thin sheet models are essential to allow shielding effectiveness of composite enclosures and vehicles to be modelled. Thin dispersive sheets are often modeled using surface impedance models in finite-difference time-domain (FDTD) codes in order to deal efficiently with the multi-scale nature of the overall structure. Such boundary conditions must be applied to collocated tangential electric and magnetic fields on either side of the surface; this is usually done on the edges of the FDTD mesh cells at the electric field sampling points. However, these edge based schemes are difficult to implement accurately on staircased surfaces. Here we present a novel face centered approach to the collocation of the fields for the application of the boundary condition. This approach naturally deals with the ambiguities in the surface normal that arise at the edges on stair-cased surfaces, allowing a simpler implementation. The accuracy of the new scheme is compared to edge based and conformal approaches using both planar sheet and spherical shell canonical test cases. Stair-casing effects are quantified and the new face-centered scheme is shown have up to 3 dB lower error than the edge based approach in the cases considered, without the complexity and computational cost of conformal techniques.
This paper reports on the outcomes of the project "Electromagnetic Monitoring of Semiconductor Ag... more This 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.
IEEE Transactions on Microwave Theory and Techniques
The inclusion of thin lossy, material layers, such as carbon based composites, is essential for m... more The inclusion of thin lossy, material layers, such as carbon based composites, is essential for many practical applications modeling the propagation of electromagnetic energy through composite structures such as those found in vehicles and electronic equipment enclosures. Many existing schemes suffer problems of late time instability, inaccuracy at low frequency, and/or large computational costs. This work presents a novel technique for the modeling of thin-layer lossy materials in FDTD schemes which overcomes the instability problem at low computational cost. For this, a 1D-subgrid is used for the spatial discretization of the thin layer material. To overcome the additional time-step constraint posed by the reduction in the spatial cell size, a Crank-Nicolson time-integration scheme is used locally in the subgridded zone, and hybridized with the usual 3D Yee-FDTD method, which is used for the rest of the computational domain. Several numerical experiments demonstrating the accuracy of this approach are shown and discussed. Results comparing the proposed technique with classical alternatives based on impedance boundary condition approaches are also presented. The new technique is shown to have better accuracy at low frequencies, and late time stability than existing techniques with low computational cost.
IEEE Transactions on Electromagnetic Compatibility, 2016
Computational solvers are increasingly used to solve complex electromagnetic compatibility (EMC) ... more Computational solvers are increasingly used to solve complex electromagnetic compatibility (EMC) problems in research, product design, and manufacturing. The reliability of these simulation tools must be demonstrated in order to give confidence in their results. Standards prescribe a range of techniques for the validation, verification, and calibration of computational electromagnetics solvers including external references based on measurement or for cross-validation with other models. We have developed a modular test-suite based on an enclosure to provide the EMC community with a complex external reference for model validation. We show how the test-suite can be used to validate a range of electromagnetic solvers. The emphasis of the test-suite is on the features of interest for EMC applications, such as apertures and coupling to cables. We have fabricated a hardware implementation of many of the test-cases and measured them in an anechoic chamber over the frequency range to 1-6 GHz to provide a measurement reference for validation over this range. The test-suite has already been used extensively in two major aeronautical research programs and is openly available for use and future development by the community.
This article describes a cuboid structured mesh generator suitable for 3D numerical modelling usi... more This article describes a cuboid structured mesh generator suitable for 3D numerical modelling using techniques such as finite-difference time-domain (FDTD) and transmission-line matrix (TLM). The mesh generator takes as its input an unstructured triangular surface mesh such as is available from many CAD systems, determines a suitable variable mesh discretisation and generates solid and surface meshes in a format suitable for import by the numerical solver. The mesher is implemented in the MATLAB language and is available as open source software.
IEEE Transactions on Electromagnetic Compatibility, 2016
The contents of an equipment enclosure, particularly printed circuit boards (PCBs), affect the en... more The contents of an equipment enclosure, particularly printed circuit boards (PCBs), affect the enclosure's shielding performance. At high frequencies this absorption can be quantified using the angle of arrival and polarization averaged absorption cross-section (ACS). However, there is no available data on the high-frequency absorption characteristics of modern PCBs. In this study we apply a reverberation chamber to the determination of the average ACS of a large number of printed circuit boards taken from contemporary information and communication technology (ICT) equipment to provide a unique and comprehensive data-set. The ACS was found to range from 4×10-4-10-2 m 2 from 2-20 GHz and different classes of PCB could be identified according to their surface characteristics. The-shadowing effect‖ of densely packed PCBs was also quantified for a subset of the PCBs. It was found that the ACS of a PCB in the stack was reduced by 20 %-40 % compared to its value when isolated. By way of a review of the general power balance analysis of an electrically large populated equipment enclosure in an external environment we show how the acquired data will be useful for future qualification methodologies for ICT enclosures and PCBs.
2010 IEEE International Symposium on Electromagnetic Compatibility, 2010
This is a repository copy of Double-Weibull distributions of the re-emission spectra from a non-l... more This is a repository copy of Double-Weibull distributions of the re-emission spectra from a non-linear device in a mode-stirred chamber.
10Th International Symposium on Electromagnetic Compatibility, 2011
ABSTRACT This paper details development of human body models for use in simulations for EMC certi... more ABSTRACT This paper details development of human body models for use in simulations for EMC certification and testing of aircraft. Current models are reviewed and their unsuitabilities for the task in hand are highlighted, which chiefly arise from inappropriate levels of complexity resulting in unfeasible computational loads. Tissue layering close to the body's surface is investigated, as are the frequency-dependent properties of the relevant tissues, to give a model of human interaction with EM fields over a broadband frequency range. For a preliminary model, lossy dielectric spheres are simulated loading a cavity, and results are compared. These are found to be inadequate and a new model is developed, using layered dielectric cylinders to give a better fit to the body's EM characteristics while still maintaining relative simplicity compared to the anatomically correct models previously reviewed.
2014 International Symposium on Electromagnetic Compatibility, 2014
ABSTRACT This paper describes the effect of high temperature ageing on the electromagnetic emissi... more ABSTRACT This paper describes the effect of high temperature ageing on the electromagnetic emissions of a number of PIC microcontrollers. The aged devices show a measureable shift in the frequency of emissions. Shift in the voltage-current characteristics of the device output pins has also been observed.
Staircasing of surfaces is a known and well documented source of error in FDTD models on orthogon... more Staircasing of surfaces is a known and well documented source of error in FDTD models on orthogonal structured meshes; however, very little work focuses on such errors in simulations of electromagnetic cavities. This work examines the different errors that arise as a direct result of using an orthogonal approximation of a hollow spherical shell. The spherical shell used has a radius of 1 m and is constructed of a simple material with a conductivity σ = 1000 S/m and a thickness h = 1 mm. This material was represented using a thin boundary SIBC model allowing a mesh size much larger than the thickness of the material. The orthogonally meshed sphere was illuminated using a planewave and the electric field measured at the centre allowing the shielding effectiveness (SE) to be calculated.
The averaged absorption cross section (ACS) of a lossy object characterises its ability to captur... more The averaged absorption cross section (ACS) of a lossy object characterises its ability to capture power from diffused electromagnetic waves. The averaged ACS is very important in many EMC research areas such as indoor wireless channel modelling and human safety exposure study. The measurement of averaged ACS in a reverberation chamber can be achieved by measuring the rate of power loss in the time domain, however this technique requires dense frequency sampling for taking the inverse Fourier transform, which is very time consuming. A new scenario which accelerates the measurement speed is presented in this paper. It combines the technique of non-linear curve fitting to the power delay profile, segmented frequency sweeping and continuous mode stirring. The scenario was validated by measuring the averaged ACS of a hollow plastic sphere filled with deionized water in an EMC reverberation chamber. Measurement results showed a good accordance with the simulations and the measurement unc...
The indirect two-port reflection method for measuring antenna impedances is reviewed using scatte... more The indirect two-port reflection method for measuring antenna impedances is reviewed using scattering parameter techniques and developed into a more accurate low perturbation optically coupled transmission measurement. This transmission measurement infers the antenna impedance by measuring the voltage induced in a number of loads connected to the antenna port with reference to the antenna used for illumination. Both these techniques have proved to be very versatile: applications to a typically electromagnetic compatibility problem, consisting of a box and wire above a ground plane, and to the design of a challenging multi-band Digital Audio Broadcast antenna are presented. INTRODUCTION In this paper we propose to present our latest results to illustrate the flexibility of the technique. The first application is a classical box-wire-box system, where the radiation impedance is solved by measuring the reflection coefficient from the probe antenna. The second application is an antenna ...
A new broad-band antenna structure specifically designed for antenna position stirring in a rever... more A new broad-band antenna structure specifically designed for antenna position stirring in a reverberation chamber is described. The antenna features a reactive rotating source coupler that overcomes the problems of cable and connector reliability and stability often encountered in antenna source stirring due to cable movement. The stirring performance of the new antenna is evaluated by observation of the reduction in Rician K-factor facilitated by the antenna.
2017 International Conference on Electromagnetics in Advanced Applications (ICEAA), Sep 1, 2017
Diffusion equation based modeling has been proposed for mapping the reverberant component of th... more Diffusion equation based modeling has been proposed for mapping the reverberant component of the electromagnetic field in enclosures at high frequencies. Preliminary evaluation of the electromagnetic diffusion model using a dimensional reduction approach showed promising results compared to measurements. Here we develop a full three-dimensional diffusion model of the experimental canonical test cases considered in the preliminary evaluation and obtain finite element method solutions. The results are compared to those of the two-dimensional models. We find that the two-and three-dimensional models are generally in excellent agreement for the pseudo two-dimensional test-cases considered. Some deviations between the two-and threedimensional models are observed due to the fact the point source must be effectively represented by a line source in the reduced model. The three-dimensional model is still highly efficient compared to other applicable techniques, offering the prospect of a radical reduction in the resources required for simulating reverberant fields in electrically large structures.
IEEE Transactions on Microwave Theory and Techniques
Thin sheet models are essential to allow shielding effectiveness of composite enclosures and vehi... more Thin sheet models are essential to allow shielding effectiveness of composite enclosures and vehicles to be modelled. Thin dispersive sheets are often modeled using surface impedance models in finite-difference time-domain (FDTD) codes in order to deal efficiently with the multi-scale nature of the overall structure. Such boundary conditions must be applied to collocated tangential electric and magnetic fields on either side of the surface; this is usually done on the edges of the FDTD mesh cells at the electric field sampling points. However, these edge based schemes are difficult to implement accurately on staircased surfaces. Here we present a novel face centered approach to the collocation of the fields for the application of the boundary condition. This approach naturally deals with the ambiguities in the surface normal that arise at the edges on stair-cased surfaces, allowing a simpler implementation. The accuracy of the new scheme is compared to edge based and conformal approaches using both planar sheet and spherical shell canonical test cases. Stair-casing effects are quantified and the new face-centered scheme is shown have up to 3 dB lower error than the edge based approach in the cases considered, without the complexity and computational cost of conformal techniques.
This paper reports on the outcomes of the project "Electromagnetic Monitoring of Semiconductor Ag... more This 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.
IEEE Transactions on Microwave Theory and Techniques
The inclusion of thin lossy, material layers, such as carbon based composites, is essential for m... more The inclusion of thin lossy, material layers, such as carbon based composites, is essential for many practical applications modeling the propagation of electromagnetic energy through composite structures such as those found in vehicles and electronic equipment enclosures. Many existing schemes suffer problems of late time instability, inaccuracy at low frequency, and/or large computational costs. This work presents a novel technique for the modeling of thin-layer lossy materials in FDTD schemes which overcomes the instability problem at low computational cost. For this, a 1D-subgrid is used for the spatial discretization of the thin layer material. To overcome the additional time-step constraint posed by the reduction in the spatial cell size, a Crank-Nicolson time-integration scheme is used locally in the subgridded zone, and hybridized with the usual 3D Yee-FDTD method, which is used for the rest of the computational domain. Several numerical experiments demonstrating the accuracy of this approach are shown and discussed. Results comparing the proposed technique with classical alternatives based on impedance boundary condition approaches are also presented. The new technique is shown to have better accuracy at low frequencies, and late time stability than existing techniques with low computational cost.
IEEE Transactions on Electromagnetic Compatibility, 2016
Computational solvers are increasingly used to solve complex electromagnetic compatibility (EMC) ... more Computational solvers are increasingly used to solve complex electromagnetic compatibility (EMC) problems in research, product design, and manufacturing. The reliability of these simulation tools must be demonstrated in order to give confidence in their results. Standards prescribe a range of techniques for the validation, verification, and calibration of computational electromagnetics solvers including external references based on measurement or for cross-validation with other models. We have developed a modular test-suite based on an enclosure to provide the EMC community with a complex external reference for model validation. We show how the test-suite can be used to validate a range of electromagnetic solvers. The emphasis of the test-suite is on the features of interest for EMC applications, such as apertures and coupling to cables. We have fabricated a hardware implementation of many of the test-cases and measured them in an anechoic chamber over the frequency range to 1-6 GHz to provide a measurement reference for validation over this range. The test-suite has already been used extensively in two major aeronautical research programs and is openly available for use and future development by the community.
This article describes a cuboid structured mesh generator suitable for 3D numerical modelling usi... more This article describes a cuboid structured mesh generator suitable for 3D numerical modelling using techniques such as finite-difference time-domain (FDTD) and transmission-line matrix (TLM). The mesh generator takes as its input an unstructured triangular surface mesh such as is available from many CAD systems, determines a suitable variable mesh discretisation and generates solid and surface meshes in a format suitable for import by the numerical solver. The mesher is implemented in the MATLAB language and is available as open source software.
IEEE Transactions on Electromagnetic Compatibility, 2016
The contents of an equipment enclosure, particularly printed circuit boards (PCBs), affect the en... more The contents of an equipment enclosure, particularly printed circuit boards (PCBs), affect the enclosure's shielding performance. At high frequencies this absorption can be quantified using the angle of arrival and polarization averaged absorption cross-section (ACS). However, there is no available data on the high-frequency absorption characteristics of modern PCBs. In this study we apply a reverberation chamber to the determination of the average ACS of a large number of printed circuit boards taken from contemporary information and communication technology (ICT) equipment to provide a unique and comprehensive data-set. The ACS was found to range from 4×10-4-10-2 m 2 from 2-20 GHz and different classes of PCB could be identified according to their surface characteristics. The-shadowing effect‖ of densely packed PCBs was also quantified for a subset of the PCBs. It was found that the ACS of a PCB in the stack was reduced by 20 %-40 % compared to its value when isolated. By way of a review of the general power balance analysis of an electrically large populated equipment enclosure in an external environment we show how the acquired data will be useful for future qualification methodologies for ICT enclosures and PCBs.
2010 IEEE International Symposium on Electromagnetic Compatibility, 2010
This is a repository copy of Double-Weibull distributions of the re-emission spectra from a non-l... more This is a repository copy of Double-Weibull distributions of the re-emission spectra from a non-linear device in a mode-stirred chamber.
10Th International Symposium on Electromagnetic Compatibility, 2011
ABSTRACT This paper details development of human body models for use in simulations for EMC certi... more ABSTRACT This paper details development of human body models for use in simulations for EMC certification and testing of aircraft. Current models are reviewed and their unsuitabilities for the task in hand are highlighted, which chiefly arise from inappropriate levels of complexity resulting in unfeasible computational loads. Tissue layering close to the body's surface is investigated, as are the frequency-dependent properties of the relevant tissues, to give a model of human interaction with EM fields over a broadband frequency range. For a preliminary model, lossy dielectric spheres are simulated loading a cavity, and results are compared. These are found to be inadequate and a new model is developed, using layered dielectric cylinders to give a better fit to the body's EM characteristics while still maintaining relative simplicity compared to the anatomically correct models previously reviewed.
2014 International Symposium on Electromagnetic Compatibility, 2014
ABSTRACT This paper describes the effect of high temperature ageing on the electromagnetic emissi... more ABSTRACT This paper describes the effect of high temperature ageing on the electromagnetic emissions of a number of PIC microcontrollers. The aged devices show a measureable shift in the frequency of emissions. Shift in the voltage-current characteristics of the device output pins has also been observed.
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Papers by Ian Flintoft