overview of feko for efficiently solving emc problems with ... · pdf fileoverview of feko for...

Overview of FEKO for Efficiently Solving EMC Problems with Numerical Simulations

Dr. Markus Schick, Director Electromagnetic Solutions – EMEA

3rd September 2015

Introduction and FEKO Technology

Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.

3EMC Türkiye 2015, Istanbul, 3rd September 2015

Introduction: What is FEKO?

• FEKO is a global leading electromagnetic simulation software suite that uses

multiple frequency and time domain techniques with true hybridization to analyse

and solve a broad spectrum of problems



Introduction: Applications

Electromagnetic Compatibility (EMC)

Multiphysics Analysis and Optimization

Antenna Design Others ScatteringAntenna Placement



FEKO Applications Antenna Design, Placement and RCS

scattering

antenna design

antenna arrays

antenna placement

Antennas for wireless

communication devices and

systems (FM, GPS, 3G, TV, LTE,

MIMO and many others), reflector

antennas, antennas for radars,

antennas with radomes, ….

Arrays of microstrip patches,

waveguide-based elements, reflect

arrays, …

Placement of antennas on vehicles,

aircraft, satellites, ships, cellular

base-stations, towers, buildings,

including radiation patterns, co-site

interference and RADHAZ analysis,

…

RCS analysis and studies for aircraft,

vehicles (e.g. tanks), ships, buildings

and wind turbines …



EMC analysis

cable coupling

FEKO Applications EMC and Cable Coupling

• EMS and EMI analysis and design cases, which involve cables, which

either radiate through imperfect shields and cause coupling into other

cables, devices or antennas, or which receive (irradiation) external

electromagnetic fields (radiated from antennas or leaked through other

devices) and then cause disturbance voltages and currents potentially

resulting in a malfunctioning of the system.

• Electric and magnetic shielding for metallic or dielectric enclosures of

arbitrary shape with arbitrary opening cuts into them.

• Near fields for radiating hazard analysis.

• Elecromagnetic pulses (EMP), lightning effects and High Intensitivy

Radiated Fields (HIRF).



Introduction: Main industries

Aerospace

Automotive

Defense

Communications Consumer Electronics

Energy

Healthcare



Solvers in FEKO – Simulation Map

EL

EC

TR

ICA

L S

IZE

COMPLEXITY OF MATERIALS

FDTD

FEM

MLFMM

MoM

UTD

PO/RL-GO

Full-wave

Methods

(physicallyrigorous solution)

Asymptotic

Methods

(high-frequencyapproximation)

Hybridization to solve large and

complex problems

General study Cycle



General study cycle

Circuit Design Antenna Design

Cables analysisPCB or circuit connection

Antenna Integration

Antenna Placement and RCS analysis

EMC aspects: HIRF, Lightning,

Interferences,…Radiation Hazards Radiation Hazards

Solution Scaling with Frequency



Solution Scaling: SAAB JAS-39 Gripen

14,6 m

8,23 m

3,37 m

Aircraft model used for the benchmark

• Doubling the solution frequency,

requires that the triangle mesh size is

halved

• This increases the number of mesh

elements, resulting in an increase in

the computational requirements

• This benchmark illustrates how

computational resources scale with

frequency, comparing requirements

for MLFMM and PO methods



Electrical Size of the Aircraft

Frequency Electrical Size of Aircraft

Length Wing span

300 MHz 15 λ 9 λ

600 MHz 30 λ 17 λ

1.2 GHz 61 λ 34 λ

2 GHz 101 λ 57 λ

10 GHz 504 λ 284 λ

20 GHz 1009 λ 568 λ

300 MHz 600 MHz 1.2 GHz



Computation Resource Scaling

• Memory and runtime scaling for the SAAB JAS-39 Gripen:• The results are normalized (300 MHz, MLFMM = 1) to highlight the factor increase in

requirements as a function of increasing frequency• Furthermore, the graphs highlight the difference between requirements in the MLFMM and PO

methods: PO can solve the problem at 20 GHz where the plane is 1000λ long

Solution time scalingMemory scaling

2x Quad core Intel Xeon E5606 CPU, 2.13 GHz (8 processes total), 72 GB RAMMulti-threaded parallel processing was used on all 8 cores



Comparison of Results: MLFMM and PO

1.2 GHz 2.0 GHz

Aerospace



Simulating Composite Material Airframes

• F5 aircraft with carbon fibre construction• Fibre:

• Conductivity = 4x104 S/m• Relative permittivity = 3.4

• Epoxy: (orthogonal to fibre)

• Conductivity = 50 S/m• Relative permittivity = 3.4

• Compute:• Monostatic RCS

• Surface current distribution

• Excitation:• Linearly polarised

plane wave

Metallic

Carbon fibrealignment

Metallic

Incident wave polarisation



Simulating Composite Material Airframes

Elevation RCS at 50 MHz Surface current distribution

Azimuth RCS at 50 MHz

Carbon fibre Metallic

Surface current distribution

Carbon fibre Metallic

EMCLightning Incident on an Aircraft



Why FEKO for lightning?

• Frequency-domain analysis• Time-domain codes need too many time steps

due to the low frequency components of the

lightning spectrum

• Exceptionally low noise floor• Inherent stability of MoM formulation

• Ability to simulate reliably down to a few Hz

• Efficient analysis of cable bundles

• Schematic capability• Add sources, components, terminations

and probes

• Time-analysis capability in POSTFEKO



Cables in aircraft

Initially cables are just modelled as conductors easy to reproduce in measurement



Currents with and without shielding

Important to know how much shielding is enough.

Don’t want to add too much weight and don’t want to lose flexibility.

Up to 1400 mA for unshielded cables

Up to 21 mA for shielded cables

Lightning‐induced currents observed at the shorted ends of the three unshielded cables

Helicopter Study



Study: interference between HF and VOR system

VOR RX 1

VOR RX 2

2 channels



VOR antenna

VOR RX 1

VOR RX 2

Interference betweenHF and VOR system

Interferences on the VOR system when the HF

antenna is used

Study: interference between HF and VOR system



2 Coaxial channelsVOR 1 & VOR 2

VOR 1

VOR 2

VOR RX 1

VOR RX 2

Study: Cable analysis

VOR 1

VOR 2

HF antenna



Spurious currents induced on the VOR cables


VOR 1VOR 2



2 Coaxial channelsVOR 1 & VOR 2

VOR 1

VOR 2

VOR RX 1

VOR RX 2

VOR 1

VOR 2

VOR 1

VOR 2

Adding shieldsaround the coaxial

bundle





Spurious currents levelattenuated

VOR 1VOR 1




Spurious currents levelattenuated

VOR 2VOR 2



- Interferences was noticed between HF and VORsystem

- Cable analysis was performed to identify theinterference phenomenon

- Strong spurious currents are induced on the coaxialVOR cables.

- Additional shield around VOR coaxial cablesreduced significantly the spurious currents (morethan 15x)

Study summary:

Study: Summary



Perspectives: Lighting strike on Helicopter platform

Strikepoint

Exitpoint




Strikepoint

Exitpoint

• Lightning strikes aircraft

• Investigate:– Antenna coupling

– Coupling to cables in aircraft

• Impressed current sources for strike and exit points

• Broad-band characterisation of frequency response of platform

– 1 kHz to 1 MHz in current example

– Double exponential pulse form

– Fast computation using AFS technology in FEKO

– Surface meshing efficiency using MoM / MLFMM




Strikepoint

Exitpoint

• Lightning strikes aircraft

• Investigate:– Antenna coupling

– Coupling to cables in aircraft

• Impressed current sources for strike and exit points

• Broad-band characterisation of frequency response of platform

– 1 kHz to 1 MHz in current example

– Double exponential pulse form

– Fast computation using AFS technology in FEKO

– Surface meshing efficiency using MoM / MLFMM



• Special shielding materials can be specified in FEKO

– E.g. carbon fibre, low conductivity composites

• Such materials can be arbitrarily applied to any body panel

• Perspectives:

Comparative simulation runs will test whether such materials improve shielding performance.

Study of different cable shield configurations


Vehicles



Antenna Placement on Vehicles

• Evaluate communication blind spots

for vehicle antennas.

• Radiation hazard studies for

personnel next to or inside vehicle.

• Antenna coupling



Radiation Hazards of Multiple Transmitters (1)

• FEKO example (3 x monopole mounted on vehicle):• Compute radiation levels for each transmitter

• POSTFEKO Lua scripting:• Compute percentage contributions for each monopole

• Sum percentage contributions

• Render isosurfaces of maximum exposure boundaries

• Render field planes where colouring represents exposure levels

100 MHz 150 MHz 300 MHz



Radiation Hazards of Multiple Transmitters (2)

• Combined radiation hazard: 3 transmitters simultaneously transmitting

Percentage exposure levels (red = 100%)

Combined maximum exposure isosurfaces



ICNIRP Radiation Hazard Zones

• ICNIRP radiation hazard zones for TETRA vehicle mounted radio

• Yellow - Public safety zone

• Red - Occupational safety zone

Naval



Naval Antenna Placement

Effect of slanting

Effect of shielding-disc size

Antenna mounting options

Determine effect (patterns and isolation) of positional changes

PCB Level EMI



PCB Board Level EMI – Noise Coupling Analysis

Complex PCB geometries (ODB++ or Gerber formats) can be imported into

FEKO for board level analysis, including:

• Noise interference with antenna feeds and sensitive components

• Coupling between traces and layers

• Component placing and shielding analysis

Case study related to board level noise coupling

• The goal of the study was to investigate noise coupling

from various noise sources to the antenna feed port

• CMA was chosen due to the insight obtained

through modal analysis and modal currents

• A modification was purposed which successfully

reduced the coupling issue

multilayer PCB geometry for the study



basic more detailed with traces with antenna

mod

e #1

mod

e #3

mod

e #2

Incremental Detail Effect on Modal Current

The dominant modal behaviour is determined by the larger details on the board, and the antenna, the incremental detail

has a negligible effect on the modal current distribution



Reduced Coupling on Modified Design

Modal current, mode #3, 1.7 GHz - original geometry Modal current, mode #3, 1.7 GHz – modified geometry

S12_partial coupling mode #3 - original geometry S12_partial coupling mode #3 – modified geometry



S-parameter Coupling Verification

After problematic noise coupling was identified at 1.7 GHz, a design modification to the problematic area alleviates the interference.

The CMA investigation was verified with an S-parameter simulation: the coupling between the noise sources and the

antenna feed was calculated. The S-parameter data also verifies that the design modification will reduce the coupling.

Shielding Effectiveness




Shielding effectiveness for a PC tower • The goal of this study is to investigate the shielding

effectiveness for a PC tower

• The tower is radiated from the front at different

frequencies and the field leakage into the tower is

studied

• Although the tower is electrically large at higher

frequencies, the detailed geometry and holes of the

shielding make it suitable to solve with FDTD

combined with GPU acceleration; furthermore a

single FDTD run can capture the behavior at across

the broad frequency spectrum

• Field results are compared at different frequencies

to understand the effectiveness of the tower

shielding

Cut plane through the center of the tower geometry: the tower is 44x90x136 cm




Around 1 GHz the spacing between the boards acts like a cavity causing standing wave patterns in the tower where some areas inside are better shielded than other areas. At higher frequencies more field leaks into the tower and the field spreads more evenly through the tower.

1 GHz 6.5 GHz 12 GHz

Implant Antenna Design and Safety



Pacemaker Antenna Design

• Initial antenna performance simulated with homogeneous flat

phantom• the device is positioned 5mm below the surface and simulated with

MoM solver

• The performance is then verified using an anatomical model

(humanbodymodels.com) • the pacer is positioned accordingly in the phantom and simulated with

the FDTD solver

• The link budget shows that device telemetry will be possible up to

10m for -31dB antenna source power

[1] Design of an Implanted Compact Antenna for an Artificial Cardiac Pacemaker System, S. Lee, et al, IEICE Electronics Express,Vol. 8, No. 24, 2112-2117

low profile, high gain PIFA design for ISM band(400 MHz) [1]

generic pacemaker can and antenna housing volume ~ 40mm x 40mm x 8mm

total gain

surface currents



Antenna Design for Implanted Pacemaker

• Comparison of 2 different antenna designs

at 2 different operating frequencies

• Design #1: monopole design at 900 MHz

• Design #2: PIFA design at 400 MHz offers

superior gain performance than design #1



Pacemaker Antenna SAR Compliance

1g cube (IEEE Standards)

10g cube (ICNIRP Guidelines, CENELEC Procedures)

StandardBasic Restriction

[W/kg]

Factor below

Standard (%)

IEEE (North America)

2W/kg 1g cube 1.3%

ICNIRP (Europe) 2W/kg 10g cube 0.367%



Implant Safety for MRI - Transfer Function

• Implants need to be certified for safe usage

in MRI systems (SAR, temperature)

• Simulating the full simulation MRI + human +

implant is too complex when the implant lead

is consider, and must be solved in steps:• the implant and lead are simulated in a

homogeneous liquid with properties similar to

muscle tissue

• a transfer function for the lead is derived to

determine the response for a 1 V/m tangential

piecewise, excitation along the length of the lead

• with the knowledge of the transfer function and

incident field, the SAR and heating due to the RF

MRI field can be estimated at the lead tip

[1] Calculation of MRI-Induced Heating of an Implanted Medical Lead Wire With an Electric Field Transfer Function, Sung-Min Park, et al.



Generic Lead Transfer Functions – 64MHz

Wire geometries- bare wire (left) radius = 1.6mm

- uncapped wire (center) radius = 1.6mm, insulation radius = 2.5mm, 1cm of insulation removed on both ends

- capped wire (right) radius = 1.6mm, insulation radius = 2.5mm, 1cm of insulation removed on one end

bare wire uncapped wire capped wire

pu

bli

shed

res

ult

s [1

]F

EK

O s

imu

lati

on

res

ult

s



Implant Safety for MRI – Lead Geometry Simulation

• Despite the stepwise approach to estimate

implant safety, the simulations are still

complex when considering realistic

models • typically the leads used for the implants have

significant detail < 1mm

• multiple conductors run along the length of the

leads and are often twisted in helical

configurations to allow for flex in the lead

• FEKO’s MoM solver is well suited to this

problem: wires can be resolved with segments

reducing the computational requirements

• this can be considerably faster than e.g.

solving the problem with FDTD where many

time steps will be required due to the small

geometric detail

mrisurescan.com

cardiac pacing defibrillation and resynchronization



MRI Compatibility of a Hip Replacement

• The setup is for assessing

compliance of a hip implant in a 3T

volume coil:• at 124 MHz λmuscle ~ 30cm: could be

resonant effects• an ASTM (2009) rectangular phantom

is used for the setup• filled with muscle tissue simulating

liquid• the implant is positioned in the

phantom at a location where large field gradients occur

• field interactions, SAR distribution, and spatial peak averaged SAR values are calculated

• the temperature increase can also be calculated

ASTM phantomfilled with muscle simulating liquid

SAR distribution in the phantom showing hotspots at the tips: the peak SAR = 0.9 W/kg (0.5uT @ phantom center)

hip replacementin the phantom

length ~ 15cm λ/2 “resonance” can be seen in field distribution



Thermal Analysis in FEKO

• Lua script based implementation of the Pennes Bioheat equation, including

• SAR - metabolic processes adds heat

• Thermal conductivity - spreads heat

• Blood perfusion - removes heat (amount is temperature dependent)

• Air convection - removes heat

• Thermal radiation - removes heathttp://www.feko.info/support/lua-scripts/thermal-analysis

temperature increase near the implant tip

SAR distribution, 64 MHz temperature distribution after 10 min

40 W

20 W



Injectable Implant – 2.45 GHz

• In [1] a design is proposed at

the ISM band (2.45 GHz)• the diameter of the implant in

small enough that it can be

injected into the skin (without

surgery)

• Link budget requires antenna

gain GTX > -17dB for short range

communication < 20m

[1] Design of a Helical Folded Dipole Antenna for Biomedical Implants, Mizuno, et al.; EUCAP 2011

Ø 1mm 17.7mm

glass insulation dual folded dipole, ends terminated with a short

fat (2mm)

muscle (58mm)

-16.27 dBpeak gain

implant locationat skin muscle boundary

skin (2mm)



Thank you!

www.altairhyperworks.com/feko

overview of feko for efficiently solving emc problems with ... · pdf fileoverview of feko for...

Documents