Gabriel Anzaldi, Marcos Quilez, Pere J. Riu, Ferran Silva

1. FDTD Analysis of the Human Body Influence on a Bluetooth Link Inside a Vehicle Gabriel Anzaldi, Marcos Quilez, Pere J. Riu, Ferran Silva Electromagnetic Compatibility Group (GCEM) Technical University of Catalonia (UPC), Barcelona, Spain

2. OUTLINE • Introduction • Modeling Strategy • FDTD models • Validation Setup • Results • Conclusions

3. INTRODUCTION • Why electromagnetic numerical simulation? • Low computational cost, is it possible? • Why real car representation? • Vehicle interior scenario

4. 6.5V/m 140V/m 140V/m P7 41V/m P7 EXTERIOR SETUPS INTERIOR SETUPS INTRODUCTION GSM 1800 RADIATION BEHAVIOR Near Field Simulation Results

5. INTRODUCTION GSM-PCS 1.8 GHz RADIATION BEHAVIOR Far Field Simulation Results Exterior Source Interior Source

6. 4 5 6 1 2 3 Wire 8 9 7 INTRODUCTION SINGLE WIRE RADIATION @ 100 MHz 5 V/m 0 V/m

7. Wire 1 Wire 2 Wire 3 SUBMESHED REGIONS Wire 4 INTRODUCTION SIMPLE HARNESS COUPLING @ 100 MHz • Wires modelled implementing the following techniques: • Thin wire model. • Thin wire magnetic field correction. • Sub cell technique. • Sub cell technique + centering technique. • Sub cell technique + centering technique + FDTD out-code mesh optimization. Results Summary

8. INTRODUCTION GSM 900 SAR INSIDE VEHICLE

9. GPS Bluetooth link PDA GPS Rx INTRODUCTION BLUETOOTH RF CHANNEL WITH HUMAN PRESENCE INSIDE DE VEHICLE

10. MODELING STRATEGY MCD Optimization FDTD Model Optimization FDTD rules for large scale simulation.

11. MODELING STRATEGY CAD MODELS • DXF CAD from Crash edited and completed • Simplified as function of the specific case of study • DXF Blocks according to mesh size

12. MODELING STRATEGY FDTD MODEL Model Obtained after the import process Model Cleaned Spurious Cells Final Electromagnetic Model

13. MODELING STRATEGY FDTD LARGE SCALE RULES Centring scaling the free space values of 0 and 0 + Selective Grid Resolution Sub meshing /10, /20 or more over the interest region

14. CoarseRegion TransitionRegion SensitiveRegion MODELING STRATEGY FDTD LARGE SCALE RULES Sub meshing Non Physical Refraction

15. FDTD MODELS Human CAD model edit

16. FDTD MODELS DXF FDTD

17. FDTD MODELS Practicalinformation • Code: LC, freely distributed by Cray Research Inc. • Workstation: Dual Pro. 2.2 GHz i686 (P-III Xeon) 2 Gbytes RAM • Operating system: SMP Linux Red Hat 7.3 • The overall computational space [4.644x2.16x1.764] m3 • Simulation space truncated using MUR ABCs. • Maximum memory required was 1791 Mbytes • maximum simulation time: 5/10 hours at 300 MFlops • convergence was checked for all cases (5000/10000 t) • c=36mm, 1=18mm, 2=9mm and s=3mm.

18. FREE SPACE UPPER VIEW COARSE COARSE T TRANSITION (T) S T COARSE T COARSE SOURCE PROBES FREE SPACE LATERAL VIEW COARSE T COARSE T T S COARSE COARSE T FDTD MODELS

19. VALIDATION Anechoic Chamber 0.25 m HI-6005 Tx Rx

20. PROBE 1 PROBE 2 SOURCE RESULTS Free Space (FS) Human-Vehicle (HV) Vehicle (V)

21. RESULTS

22. E-Field plane probe RESULTS FS HV V 1 0

23. CONCLUSIONS • Electromagnetic simulations in (large) automotive environments, using low cost computational tools are practically possible. • The agreement between calculations and measurements is satisfactory • Electric field intensity varies a lot depending on source location and environment conditions for interior sources where multipath propagation, reflections and scattering are present. • Numerical methods can be applied to both radiation and couplingproblems inside a vehicle. Computation of voltages induced on wires or transmission lines produced by electromagnetic sources in the near field of the receiving wire and under the singular conditions of an almost-closed structure are possible. • Any FDTD code can produce useful results, that can be compared to experimental measurements, if simple rules are used for the modelling and theuncertaintyof the measurements is taken into account for the comparison.