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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.