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

Introduction Modeling Strategy FDTD models Validation Setup Results Conclusions OUTLINE

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

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

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

Wire Probes P1P2P3P4P5P6P7P8P9 Simulation (V/m) Measurement (V/m) V/m0 V/m SINGLE WIRE 100 MHz INTRODUCTION

Results Summary Source Wire 1 Coupling wiresMeasured (mV) Simulated (mV) C1C2C3C4C5 W W W SIMPLE HARNESS 100 MHz Wire 4 Wire 3 Wire 1 Wire 2 SUBMESHED REGIONS INTRODUCTION Wires modelled implementing the following techniques: 1.Thin wire model. 2.Thin wire magnetic field correction. 3.Sub cell technique. 4.Sub cell technique + centering technique. 5.Sub cell technique + centering technique + FDTD out-code mesh optimization.

INTRODUCTION GSM 900 SAR INSIDE VEHICLE

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

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

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

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

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

Coarse Region Transition Region Sensitive Region Non Physical Refraction Sub meshing FDTD LARGE SCALE RULES MODELING STRATEGY

FDTD MODELS Human CAD model edit

FDTD MODELS DXF FDTD

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. FDTD MODELS Practical information

FDTD MODELS COARSE TRANSITION (T) T T T T T T T FREE SPACE LATERAL VIEW FREE SPACE UPPER VIEW SS SS SOURCEPROBES

VALIDATION Tx Rx HI-6005 Anechoic Chamber 0.25 m

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

RESULTS dBV/mFSVHV P1P2P1P2P1P2 FSP P VP P HVP P

E-Field plane probe RESULTS 0 1 FS V HV

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. radiation and coupling problems inside a vehicle. Numerical methods can be applied to both radiation and coupling problems 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 the uncertainty of the measurements is taken into account for the comparison.