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 SETUPS INTERIOR 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

9 8 7

123

4 5 6

Wire

Probes

P1 P2 P3 P4 P5 P6 P7 P8 P9

Simulation (V/m) 1.04 1.66 1.02 3.86 4.08 3.09 0.19 0.64 0.72

Measurement (V/m) 0.9 1.5 0.9 3.5 3.8 2.86 0.17 0.56 0.67

5 V/m

0 V/m

SINGLE WIRE RADIATION @ 100 MHz

INTRODUCTION

Results Summary

Source Wire 1

Coupling wires Measured (mV)Simulated (mV)

C1 C2 C3 C4 C5

W 2 182 75 94 209 198 189

W 3 89 36 46 102 97 91

W4 71 29 36 65 77 73

SIMPLE HARNESS COUPLING @ 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

PDABluetooth 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 Final Electromagnetic Electromagnetic

ModelModel

MODELING STRATEGY

* ** 0º 45º , 54º

2p p

avg

v vv

/10, /20 or more over the interest region

CentringCentring

Selective Grid ResolutionSelective 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

COARSE

COARSE

COARSE

COARSE

COARSE

COARSE

COARSE

TRANSITION (T)

T

T

T

TT

T

T

FREE SPACE LATERAL VIEW

FREE SPACE UPPER VIEW

S

S

SOURCE PROBES

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/m FS V HV

P1 P2 P1 P2 P1 P2

FS P1 0 3.02 4.03 3.24 0.98 8.66

P2 -3.02 0 1.00 0.21 -2.04 5.63

V P1 -4.03 -1.00 0 -0.78 -3.04 4.63

P2 -3.24 -0.21 0.78 0 -2.25 5.42

HV P1 -0.98 2.04 3.04 2.25 0 7.67

P2 -8.66 -5.63 -4.63 -5.42 -7.67 0

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.

Numerical methods can be applied to both radiation and couplingradiation and coupling problems problems inside a vehicleinside 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.