Using FEKO for Electromagnetic Simulations in the Automotive Environment Dr. Ulrich Jakobus and Dr. Markus Schick EM Software & Systems GmbH, Germany www.emss.de
Using FEKO forElectromagnetic Simulations
in the Automotive Environment
Dr. Ulrich Jakobus and Dr. Markus Schick
EM Software & Systems GmbH, Germanywww.emss.de
www.feko.infoEHTC 2008, Strasbourg, 30.09.2008
Contents
• Introduction– Electromagnetic environment
• Computational methods– Overview– Method of Moments (MoM)– Multi-Level Fast Multipole Method (MLFMM)
• Application Example
• Summary and Conclusion
www.feko.infoEHTC 2008, Strasbourg, 30.09.2008
Real-World EM Problems
• Antenna analysis in complex environments.
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Complexity of Materials
UTD
PO/GO
MOM
FEM
MLFMM
Ele
ctrica
l Siz
e3D EM Simulation Map
www.feko.infoEHTC 2008, Strasbourg, 30.09.2008
• CAD geometry model created.
• Surface mesh created.• Equivalence principle
applies, i.e. electric and magnetic currents on mesh is assumed to be unknown.
• RWG basis functions forms linear set of equations:
Z I = V• Linear set of equations
solved to find vector magnitude of currents on each mesh triangle.
MoM solution process:
Method of Moments in the Frequency Domain
Geometry Surface mesh
Linear basis functions on wire segments.
RWG basis functions on triangles.
www.feko.infoEHTC 2008, Strasbourg, 30.09.2008
Method of Moments in the Frequency Domain
• Near- and far-fields• Input impedance• S-parameters
Radiation characteristics derived from surface currents:
Surface currents Near fields Radiation patterns
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Fast multipole method (FMM)
• Multilevel implementation:– Divide space into boxes– Aggregation A– Translation T– Disaggregation D
Source region Observer region
A DT
www.feko.infoEHTC 2008, Strasbourg, 30.09.2008
Multilevel Fast Multipole Method (MLFMM)
• Memory requirement O(N2)
• CPU-time O(N3)
• Memory requirement O(N log N)• CPU-time O(N log2 N)
N N
Two levels
Conventional MoM MLFMMvs.
HUGEMemory & Runtime
Savings
• The MLFMM is as accurate as the MoM.• More generally applicable than asymptotic high frequency techniques PO and UTD.• For very large or electrically huge problems MLFMM might still be insufficient and PO or UTD required.
www.feko.infoEHTC 2008, Strasbourg, 30.09.2008
MLFMM application example: Mobile phone in a car
• Memory requirement:MLFMM 1.17 GByteMoM 209.08 GByte
• Run-time (P4 1.8 GHz):MLFMM 4 hoursMoM not solved
Mobile phone analysis in a car model at 1878 MHz
N=118 452 unknowns
www.feko.infoEHTC 2008, Strasbourg, 30.09.2008
Fender Antenna for VW Beetle
Creation of a computational model from the CAD data:• Which details are necessary (e.g. door handle)?• Transition resistances at hinges and door locks.• Lossy dielectric ground (wet, dry)• Plastic parts (e.g. bumper, seat)• Glass windscreen
www.feko.infoEHTC 2008, Strasbourg, 30.09.2008
Fender Antenna for VW Beetle
Creation of a computationalmodel from the CAD data:• Which details are
necessary (e.g. door handle)?
• Transition resistances at hinges and door locks.
• Lossy dielectric ground (wet, dry).
• Plastic parts (bumper, seats).
• Glass windscreen.
Surface current distribution(transmitting case using
reciprocity)
Horizontalfar-fieldpattern
www.feko.infoEHTC 2008, Strasbourg, 30.09.2008
Complex Antennas: Integrated into Windshield
• TV, FM, GSM antenna integrated into multilayered glass.
• Too complex to do a full 3D analysis (i.e. cannot discretise the wire strips, glass and car).
• Solution: Use coated wire equivalents.
• Solution caters for the effect of:– Multiple glass layers– Curvature of windscreen– 3D car body (important for
far- and near-field computations)
Equiv. FEKO model of a metallic wire with dielectric coating.
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Effect of Conducting Windows
• Conductive layer for thermal protection
• Effect modelled using thin dielectric sheet formulation
Far Field Gain vs Angle
Phi [Deg] at Theta = 90.00 [Deg]
With windows No Windows
0º 345º330º
315º
300º
285º
270º
255º
240º
225º210º
195º180º165º150º
135º
120º
105º
90º
75º
60º
45º30º
15º 0º0
-2
-4
-6
-8
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ICNIRP Compliance for TETRA Radio System
Low current density
High current density Maximum localised SAR
High E-field values
Low E-field values
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Tyre Pressure Sensor Radiation Analysis
Front tire antenna excitation Rear tire antenna excitation
Opposite side -53.8 dBV/m
True side -49.7 dBV/m
Opposite side -61 dBV/m
True side -55 dBV/m
Y. Yamada, K. Tanoshita, K. Nakatani, S. Horiuchi, “FEKO Simulations and Measurements of Electrical Field Distributions around a Car,” ACES 2007, Verona, Italy, March 2007
www.feko.infoEHTC 2008, Strasbourg, 30.09.2008
Optical Controller
Spectrum Analyser
Field Distributions Inside a Vehicle - VerificationM
easu
red
Sim
ula
ted
Y. Yamada, K. Tanoshita, K. Nakatani, S. Horiuchi, “FEKO Simulations and Measurements of Electrical Field Distributions around a Car,” ACES 2007, Verona, Italy, March 2007
www.feko.infoEHTC 2008, Strasbourg, 30.09.2008
EMC Coupling Problem (Exhaust Pipe)
Coupling between engine area and the receiving antenna at the rear of vehicle (resonance on exhaust at 24 MHz).
f = 24 MHz
f = 27 MHz
www.feko.infoEHTC 2008, Strasbourg, 30.09.2008
Summary and Conclusion
• Introduction– Antenna Design– Electromagnetic Environment
• Computational methods– Overview– Method of Moments (MoM)– Acceleration with Multi-Level Fast Multipole Method (MLFMM)
• Application Example– Different Antennas– Tyre Pressure System– EMC Applications