High frequency radiated field synthetic environment (HIRF SE)

image-left Funder: ERC
Date: December 2008 - July 2012
Web pages: CORDIS
My roles: Test-case leader, task leader, researcher

Air vehicles operate in an increasingly complex electromagnetic environment, with developing threats arising outside the air vehicle and the demand from passengers to operate increasing numbers of diverse personal electronic devices within the cabin in flight. Modern airframe design is also exploiting new developments in materials and structures to construct ever more efficient air vehicles that impacts on the electromagnetic performance of the vehicle.

Qualifying an air vehicle for its electromagnetic environment has traditionally been focussed on expensive and time consuming tests once prototypes are available, risking considerable remedial costs if problems are found. The HIRF SE project provided the European aeronautics industry with a computational framework to enable electromagnetic aspects of the airframe design to be accounted for at an early stage of the design process, offering the prospects of substantial economic benefits and a considerable reduction in the number of certification and qualification tests required.

placeholder image 1 — A selection of images from my work on the project

placeholder image 2 — A selection of images from my work on the project

The HIRF SE onsortium consistent of over 30 partners including Dassault Aviaition, Aleina Aeronautica, BAE Systems, Thales, Computer simulation technology, IDS, ONERA, University of York, Universidad de Granada, University of Nottingham, Universiteit Twente, Technische Universitaet Hamburg-Harburg and Universitat Politecnica de Catalunya.

As part of the UOY research effort on the project I contributed to:

Developing new models for the efficient representation of composite materials in finite-difference time-domain solvers using surface-impedance bounary conditions (Flintoft et al., 2018; Dawson et al., 2017; Flintoft et al., 2013);
A hybrid method of modelling electromagnetic penetration through fine-scale apertures in the fuselage, taking measured characteristics of the features and incorporating them into large scale computational models of the whole aircraft (Xia et al., 2013; Flintoft et al., 2012; Xia et al., 2012; Xia, Flintoft and Dawson, 2011; Xia et al., 2011);
Measurements and models of human body absorption characteristics within airframes for use in determining the effect of passengers on electromagnetic fields in vehicles and the diffuse electromagntic exposure of the passengers from those fields (Flintoft et al., 2015; Flintoft et al., 2014; Melia, Flintoft and Robinson, 2012; Melia, Robinson and Flintoft, 2012; Melia, Robinson and Flintoft, 2011; Robinson, Flintoft and Melia, 2011; Melia, Robinson and Flintoft, 2011);
The creation of validation test-suites for computational electromagnetic solvers devise specifically for electromagnetic compatibility applications (Flintoft et al., 2017; Flintoft et al., 2013; Tallini et al., 2011).

References

Flintoft, I.D., Bourke, S.A., Alvarez, J., Dawson, J.F., Cabello, M.R., Robinson, M.P. and Garcia, S.G., 2018. Face centered anisotropic surface impedance boundary conditions in FDTD. IEEE Transactions on Microwave Theory and Techniques, 66(2), pp.643–650.

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.
```
@article{Flintoft2018,
  author = {Flintoft, I. D. and Bourke, S. A. and Alvarez, J. and Dawson, J. F. and Cabello, M. R. and Robinson, M. P. and Garcia, S. G.},
  title = {Face centered anisotropic surface impedance boundary conditions in FDTD},
  journal = {IEEE Transactions on Microwave Theory and Techniques},
  year = {2018},
  volume = {66},
  number = {2},
  pages = {643-650},
  month = feb,
  doi = {10.1109/TMTT.2017.2778059},
  file = {:pdfs/TMTT66-Flintoft-643.pdf:PDF},
  keywords = {Finite-difference time-domain, impedance network boundary condition, surface-impedance boundary condition},
  postprint = {https://pure.york.ac.uk/portal/files/53616541/TMT_SIBC_postprint.pdf}
}
```
Flintoft, I.D., Dawson, J.F., Dawson, L., Marvin, A.C., Alvarez, J. and Garcia, S.G., 2017. A modular testsuite for the validation and verification of electromagnetic solvers in electromagnetic compatibility applications. IEEE Transactions on Electromagnetic Compatibility, 59(1), pp.111–118.

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.
```
@article{Flintoft2017,
  author = {Flintoft, I. D. and Dawson, J. F. and Dawson, L. and Marvin, A. C. and Alvarez, J. and Garcia, S. G.},
  title = {A modular testsuite for the validation and verification of electromagnetic solvers in electromagnetic compatibility applications},
  journal = {IEEE Transactions on Electromagnetic Compatibility},
  year = {2017},
  volume = {59},
  number = {1},
  pages = {111-118},
  month = feb,
  issn = {0018-9375},
  note = {Date of acceptance: 31/07/2016. © 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.},
  doi = {10.1109/TEMC.2016.2599004},
  file = {:pdfs/TEMC59-Flintoft-111.pdf:PDF},
  keywords = {computational electromagnetics, validation, verification, benchmark problems},
  postprint = {https://pure.york.ac.uk/portal/files/50264571/TEMC59_Flintoft_111_postprint.pdf},
  publisher = {IEEE}
}
```
Dawson, J.F., Flintoft, I.D., Bourke, S.A., Robinson, M.P., Cabello, M.R., Garcia, S.G. and Alvarez, J., 2017. Face centered anisotropic surface impedance boundary conditions in FDTD: Improved performance of staircased mesh for shielding problems. In: 2017 International Conference on Numerical Electromagnetic and Multiphysics Modeling and Optimization (NEMO). Sevilla, Spain, pp.260–262.

We present a new face centered approach to the collocation of the fields for the application of a surface impedance boundary condition (SIBC). This approach deals with the ambiguities in the surface normal that arise at the edges on stair-cased surfaces.. The accuracy of the new scheme is compared to edge based and conformal approaches using both planar sheet and spherical shell test cases. Stair-casing effects are evaluated and the face-centered scheme exhibits significantly less error than the edge based approach.
```
@inproceedings{Dawson2017,
  booktitle = {2017 International Conference on Numerical Electromagnetic and Multiphysics Modeling and Optimization (NEMO)},
  month = {17-19 May},
  address = {Sevilla, Spain},
  author = {Dawson, J. F. and Flintoft, I. D. and Bourke, S. A. and Robinson, M. P. and Cabello, M. R. and Garcia, S. G. and Alvarez, J.},
  title = {Face centered anisotropic surface impedance boundary conditions in FDTD: Improved performance of staircased mesh for shielding problems},
  year = {2017},
  pages = {260-262},
  doi = {10.1109/NEMO.2017.7964253},
  file = {:pdfs/NEMO2017-Dawson-260.pdf:PDF},
  keywords = {computational electromagnetics, electromagnetic shielding, thin boundary},
  postprint = {https://pure.york.ac.uk/portal/files/51985597/UoY_NEMO17_SIBC_v6_CR_Postprint.pdf}
}
```
Flintoft, I.D., Melia, G.C.R., Robinson, M.P., Dawson, J.F. and Marvin, A.C., 2015. Rapid and accurate broadband absorption cross-section measurement of human bodies in a reverberation chamber. Measurement Science and Technology, 26(6), p.065701.

A measurement methodology for polarisation and angle of incidence averaged electromagnetic absorption cross-section using a reverberation chamber is presented. The method is optimised for simultaneous rapid and accurate determination of average absorption cross-section over the frequency range 1 to 15 GHz, making it suitable for use in human absorption and exposure studies. The typical measurement time of the subject is about eight minutes with a corresponding statistical uncertainty of about 3% in the measured absorption cross-section. The method is validated by comparing measurements on a spherical phantom with Mie Series calculations. The efficacy of the method is demonstrated with measurements of the posture dependence of the absorption cross-section of a human subject and an investigation of the effects of clothing on the measured absorption which are important considerations for the practical design of experiments for studies on human subjects.
```
@article{Flintoft2015a,
  author = {Flintoft, I. D. and Melia, G. C. R. and Robinson, M. P. and Dawson, J. F. and Marvin, A. C.},
  title = {Rapid and accurate broadband absorption cross-section measurement of human bodies in a reverberation chamber},
  journal = {Measurement Science and Technology},
  year = {2015},
  volume = {26},
  number = {6},
  pages = {065701},
  month = jun,
  issn = {0957-0233},
  note = {© 2015 IOP Publishing. This is an author created, uncopyedited version of an article accepted for publication in IOP Measurement Science and Technology. The publisher is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at 10.1088/0957-0233/26/6/065701.},
  doi = {10.1088/0957-0233/26/6/065701},
  file = {:pdfs/MST26-Flintoft-065701.pdf:PDF},
  keywords = {absorption cross-section, reverberation chamber, specific absorption rate},
  owner = {idf1},
  postprint = {https://pure.york.ac.uk/portal/files/43360130/MST26_Flintoft_et_al_065701_postprint.pdf},
  timestamp = {2016.10.12}
}
```
Flintoft, I.D., Robinson, M.P., Melia, G.C.R., Marvin, A.C. and Dawson, J.F., 2014. Average absorption cross-section of the human body measured at 1-12 GHz in a reverberant chamber: results of a human volunteer study. Physics in Medicine and Biology, 59(13), pp.3297–3317.

The electromagnetic absorption cross-section (ACS) averaged over polarization and angle-of-incidence of 60 ungrounded adult subjects was measured at microwave frequencies of 1–12 GHz in a reverberation chamber. Average ACS is important in non-ionizing dosimetry and exposure studies, and is closely related to the whole-body averaged specific absorption rate (WBSAR). The average ACS was measured with a statistical uncertainty of less than 3% and high frequency resolution for individuals with a range of body shapes and sizes allowing the statistical distribution of WBSAR over a real population with individual internal and external morphologies to be determined. The average ACS of all subjects was found to vary from 0.15 to 0.4 m 2 ; for an individual subject it falls with frequency over 1–6 GHz, and then rises slowly over the 6–12 GHz range in which few other studies have been conducted. Average ACS and WBSAR are then used as a surrogate for worst-case ACS/WBSAR, in order to study their variability across a real population compared to literature results from simulations using numerical phantoms with a limited range of anatomies. Correlations with body morphological parameters such as height, mass and waist circumference have been investigated: the strongest correlation is with body surface area (BSA) at all frequencies above 1 GHz, however direct proportionality to BSA is not established until above 5 GHz. When the average ACS is normalized to the BSA, the resulting absorption efficiency shows a negative correlation with the estimated thickness of subcutaneous body fat. Surrogate models and statistical analysis of the measurement data are presented and compared to similar models from the literature. The overall dispersion of measured average WBSAR of the sample of the UK population studied is consistent with the dispersion of simulated worst-case WBSAR across multiple numerical phantom families. The statistical results obtained allow the calibration of human exposure assessments made with particular phantoms to a population with a range of individual morphologies.
```
@article{Flintoft2014,
  author = {Flintoft, I. D. and Robinson, M. P. and Melia, G. C. R. and Marvin, A. C. and Dawson, J. F.},
  title = {Average absorption cross-section of the human body measured at 1-12 GHz in a reverberant chamber: results of a human volunteer study},
  journal = {Physics in Medicine and Biology},
  year = {2014},
  volume = {59},
  number = {13},
  pages = {3297--3317},
  month = may,
  issn = {0031-9155},
  note = {Date of acceptance: 06/05/2014. This is an author created, uncopyedited version of an article accepted for publication in IOP Physics in Medicine. The publisher is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at 10.1088/0031-9155/59/13/3297.},
  doi = {10.1088/0031-9155/59/13/3297},
  file = {:pdfs/PMB59-Flintoft-3297.pdf:PDF},
  owner = {idf1},
  postprint = {https://pure.york.ac.uk/portal/files/43360156/PMB59_Flintoft_et_al_postprint.pdf},
  timestamp = {2016.10.12}
}
```

Flintoft, I.D., Dawson, J.F., Marvin, A.C. and Porter, S.J., 2013. Anisotropic material surface model. In: HIRF SE Stakeholder Event. Torino, Italy.

Xia, R., Dawson, J.F., Flintoft, I.D., Marvin, A.C. and Porter, S.J., 2013. Surface joint/feature macro-model. In: HIRF SE Stakeholder Event. Torino, Italy.

Flintoft, I.D., Dawson, J.F., Dawson, L. and Marvin, A.C., 2013. A modular test-case for validation of electromagnetic solvers in electromagnetic compatibility applications. In: Computational Electromagnetics for EMC 2013 (CEMEMC’13). Granada, Spain.

Melia, G.C.R., Flintoft, I.D. and Robinson, M.P., 2012. Absorption cross-section of the human body in a reverberant environment. In: EMC Europe 2012, 11th International Symposium on Electromagnetic Compatibility. [online] Rome, Italy: IEEE, pp.1–6.

Xia, R., Dawson, J.F., Flintoft, I.D., Marvin, A.C. and Porter, S.J., 2012. Use of a genetic algorithm in modelling small structures in airframes: Characterising and modelling joints, seams, and apertures. In: EMC Europe 2012, 11th International Symposium on Electromagnetic Compatibility. [online] Rome, Italy: IEEE, pp.1–5.

Flintoft, I.D., Dawson, J.F., Xia, R., Porter, S.J. and Marvin, A.C., 2012. Simulation of materials and joints in FDTD using digital filter macro-models. In: Proceedings of the 9th Ultra-Wideband, Short-Pulse Electromagnetics Conference at the European Electromagnetics Smposium (EuroEM 2008). Lausanne, Switzerland.

Melia, G.C.R., Robinson, M.P. and Flintoft, I.D., 2012. Measuring the absorption cross section of the human body. In: 3rd UK URSI Festival of Radio Science. Durham, UK.

Melia, G.C.R., Robinson, M.P. and Flintoft, I.D., 2011. Development of a layered broadband model of biological materials for aerospace applications. In: 2011 International Symposium on Electromagnetic Compatibility (EMC EUROPE 2011), 10th International Symposium on Electromagnetic Compatibility. [online] York, UK, pp.84–89.

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.
```
@inproceedings{Melia2011,
  issn = {2325-0356},
  isbn = {978-1-4577-1709-3},
  booktitle = {2011 International Symposium on Electromagnetic Compatibility (EMC EUROPE 2011)},
  month = {26-30 September},
  address = {York, UK},
  series = {10th International Symposium on Electromagnetic Compatibility},
  author = {Melia, G. C. R. and Robinson, M. P. and Flintoft, I. D.},
  title = {Development of a layered broadband model of biological materials for aerospace applications},
  year = {2011},
  pages = {84--89},
  file = {:pdfs/EMCE2011-Melia-84.pdf:PDF},
  keywords = {aircraft testing;biological effects of fields;biological tissues;electromagnetic compatibility;EM fields;EMC certification;aerospace applications;aircraft testing;biological materials;body surface;dielectric cylinders;frequency-dependent properties;human body model;human interaction;layered broadband model;lossy dielectric spheres;tissue layering;Aircraft;Atmospheric modeling;Biological system modeling;Electromagnetic compatibility;Muscles;Phantoms;Solid modeling},
  owner = {idf1},
  timestamp = {2013.09.17},
  url = {http://ieeexplore.ieee.org/document/6078495}
}
```

Robinson, M.P., Flintoft, I.D. and Melia, G.C.R., 2011. People and planes: Development of broadband EMC models of biological materials in aircraft. In: Proceedings of the XXXIInd General Assembly and Scientific Symposium of the International Union of Radio Science. Montreal, Canada, pp.1–4.

Tallini, D., Dawson, J.F., Flintoft, I.D., Kunze, M. and Munteanu, I., 2011. Virtual HIRF tests in CST STUDIO SUITE;. A reverberant environment application. In: Proceedings of the 2011 International Conference on Electromagnetics in Advanced Applications, ICEAA2011. Torino, Italy, pp.849–852.

Xia, R., Dawson, J.F., Flintoft, I.D., Marvin, A.C., Porter, S.J. and Marschke, I., 2011. Building electromagnetic macro models for small structures on aircraft; Characterising and modelling joints, seams, and apertures. In: 2011 International Symposium on Electromagnetic Compatibility (EMC EUROPE 2011), 10th International Symposium on Electromagnetic Compatibility. [online] York, UK, pp.575–580.

Melia, G.C.R., Robinson, M.P. and Flintoft, I.D., 2011. EMC and people on planes: Development of a layered broadband model of biological materials for aerospace applications. In: 2nd UK URSI Festival of Radio Science. Leicester, UK.

Xia, R., Flintoft, I.D. and Dawson, J.F., 2011. Building electromagnetic models for small structures on aircraft. In: 2nd UK URSI Festival of Radio Science. Leicester, UK.