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FEKO – moderne effiziente

Softwarelösungen für EMV-

Problemstellungen

Dipl.-Ing.Torben Voigt, Application Engineer

7th March 2016

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

2

Introducing FEKO

FEKO is a global leading state of the art computer code that uses

various frequency and time domain techniques to analyse a broad

spectrum of electromagnetic problems.


3

Real-World EM Problems

Antenna Research and Development


4


Antenna Analysis in Complex Environment


5


EMC Analysis (Radiation, Coupling, Shielding)


6

Solvers in FEKO – Simulation MapE

LE

CT

RIC

AL

SIZ

E

COMPLEXITY OF MATERIALS

FDTD

FEM

MLFMM

MoM

UTD

PO/RL-GO

Full-wave

Methods

(physically

rigorous solution)

Asymptotic

Methods

(high-frequency

approximation)

Hybridization to

solve large and

complex

problems


7

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 …


8

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.

• Electromagnetic pulses (EMP), lightning effects and High Intensity

Radiated Fields (HIRF).


9

Industry Sectors

Immunity and Emissions


11

EMC Testing: Immunity Tests

DUT

EMC Antenna


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EMC – PCB Emissions on a High Level System

Source: http://www.apag-elektronik.com/products/automotive-electronics.html

Courtesy of Cadence Design Systems


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Importing PCB Near Fields into FEKO

• Simulated near fields of the PCB are imported into FEKO as an equivalent source

for a high level simulation, which includes an antenna and a cable harness in a

car

Cable Harness

Windscreen

Antenna


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Coupling from PCB on back left light to DAB antenna feed

Shielding Effectiveness


16

Susceptibility Example – With Enclosure


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Results Comparison: Currents vs Frequency

Plate and wire

Enclosure with wire

Frequency

Curr

ents


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Shielding Effectiveness

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

Cable Coupling


20

Cable Modelling – Interconnections and Terminations

• 3D harness projected onto a 2D plane (XY, XZ or YZ plane)

• Components can be added at each connector


21

Cable Modelling: Cable Types

Shield types supported; computation of

transfer impedance (ZT) and admittance

(YT)

• Schelkunoff (solid) model – ZT

• Kley (braided) formulas – ZT and YT

Interpolation of user imported data

• ZT and YT

Measured data for > 20 popular coaxial

cable types included in FEKO

m = 24, n = 8,

d = 0.1 mm, = 25.7

Kley, K., “Optimized Single-Braided Cable Shields”,

IEEE Trans. On Electromagnetic Compatibility, Vol.

35, No. 1, pp. 1-9, Feb 1993


22

RG58 Coax Cable above Ground Plane with Gap

• Radiation problem

• Two different ground plane arrangements

• Common ground between source at CC_Port1 and load at CC_Last

• Separate grounds (2 cm apart) between cable source and load leaving a gap

• Separate grounds structures restricts usage of standard MTL

techniques

• Output: S21 from coax cable to nearby antenna


23

RG58 Coax Cable above Ground Plane with Gap (II)

(a) (b)

Automotive Cable Coupling

Case Study


25

Induced voltage at antenna terminal

E-field radiated

by cable

Currents induced

on body

Computation results: RadiationCable signals coupling to antenna terminal


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Computation results: Irradiation3G antenna coupling to cable terminals

Induced voltage at tail light

E-field near

cable path

Current

distribution

Source

Examples Related to Electric

and Hybrid Cars


28

Wireless Charging for Electrical and Plug-in Hybrid Cars

• Wireless charging for electric and plug-in hybrid cars is a topic of

interest today so to develop automatic electrical charge systems on the

road or at home in the near future. For such systems, efficiency,

distance, standarizations, and other aspects are now under discussion /

development.

• FEKO is being used for the analysis and design of the antennas for such

wireless charging systems.

Radiation Hazard


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Antenna Performance Verification and Compliance

FEKO is used to predict the integrated antenna

performance and compliance investigations,

reducing the risk of noncompliance for the

final product

• Typical real-world test environments: against the

head, hand effect, different grips, inside a

vehicle, etc.

• Spatial peak averaged SAR (IEEE 1528)

• CTIA over-the-air OTA parameters including

efficiency and TRP

Antenna performance verification

SAR compliance testing

SAR distribution in the head

phantom, the red cube shows the

location of the spatial peak averaged

1g SAR = 0.854 W/kg


31

FEKO for RF Safety/ Radiation Hazard

What is radiation hazard?

• Transmitters mounted on or in vehicles may need to be certified to ensure that the

EM fields absorbed in passengers comply with the relevant standards, depending

on the operational frequency and power levels

• Standards (e.g. ICNIRP, FCC) use peak field levels and specific absorption rate

(SAR) as a measure to quantify safety

• IEEE 1528.2 is deals with vehicle mounted antennas and absorption for

passengers and bystanders


32

Radiation Hazard for Multiple Transmitters

• RF safety certification for multiple vehicle

mounted transmitters

• The goal of this study was to investigate RF safe

zones for 3 vehicle mounted antennas

• The safe zones are determined by the field levels

being below the levels required by the standards

• Each transmitter contributes to cumulative

radiation levels

• ICNIRP radiation hazard standard:

• Compute percentage of radiation limit at transmit

frequency for each contribution

• Sum percentage contributions for all transmitters

• Evaluate “combined” radiation levels against

standard:

e.g. 10% (100 MHz) + 15% (150 MHz) + 20% (300

MHz) = 45% of maximum exposure level

• Determine general public and occupational safe

zones


33

ICNIRP Radiation Hazard Zones

• ICNIRP radiation hazard zones for TETRA vehicle mounted radio

• Yellow - Public safety zone

• Red - Occupational safety zone

EMC

Lightning Incident on an Aircraft


35

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


36

Cables in aircraft

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


37

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

Naval Applications


39

Naval Antenna Placement

Effect of

slanting

Effect of shielding-disc size

Antenna mounting options

Determine effect (patterns and isolation)

of positional changes


40

Optimal Antenna Layout

• Investigate pattern change w.r.t. antenna position.

• Compare models: top mast section only vs. top mast

and top decks

• How is the quality of a radiation pattern determined?

Implant Antenna

Design and Safety


42

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


43

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


44

Pacemaker Antenna SAR Compliance

1g cube (IEEE Standards)

10g cube (ICNIRP Guidelines, CENELEC Procedures)

Standard

Basic Restriction

[W/kg]

Factor below

Standard (%)

IEEE (North

America)

2W/kg 1g cube 1.3%

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


45

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


46

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 phantom

filled 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 replacement

in the phantom

length ~ 15cm λ/2

“resonance” can be

seen in field

distribution


47

Changes in FEKO 14


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Changes in FEKO 14


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Changes in FEKO 14


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Changes in FEKO 14


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Changes in FEKO 14


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Thank you!

www.altairhyperworks.com/feko

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