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EMC analysis workflow
Antonio Ciccomancini Scogna, CST of America –
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
Antonio Ciccomancini Scogna, CST of America –
EMC/EMI Applications
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
Emissions Susceptibility E3
Typical Emissions Issues
1 2
Image courtesy of Johnson Controls Inc.
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Coupling between heat sink
and connector bypasses signal
path through PCB
Coupling through
vent in enclosure
1Slots in ground plane
radiate onto cable, DM to
CM current conversion
� EMC design involves minimizing the noise, absorbing the noise, containing the noise (shielding) and diverting/filtering the
noise.
� Stray fields/couplings/radiation are critical in EMC/EMI. Capturing these effects accurately often requires full system-level
simulation.
USB Channel Application
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� USB differential pair with intended differential mode
signals and unintended common mode signals
� Several potential coupling paths that may lead to
emissions effects
USB cable
3 meter radiated emissions
results
Emissions Workflow: USB Channel
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Import PCB layout into CST PCB STUDIO and run CST BOARDCHECK to identify critical nets
Perform detailed analysis of critical nets using CST Microwave STUDIO and compute transient CM voltage
Use transient CM voltage to simulate radiation from USB
cable
Cascading approach is only valid if the system can be decoupled
CST BOARDCHECK1. Deal with a new PCB layout
2. Analyze PCB in EMC rule checker
5. Obtain EMC rules for layout engineers Design
Cycle
EMC Rules Checking for PCB Designs
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3. Decide which structures need simulation
4. Perform simulations and analyze results
EMC Rule Checking Workflow
• Altium (ODB++), Cadence, Mentor Graphics, Zuken
Import PCB Design
• Categories: Signal reference, Wiring/Crosstalk, Decoupling, Placement
Select EMC Rules
Select Nets
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• Tag critical nets, differential pairs, or power and ground nets
Select Nets
• Tag ICs, clock drivers, stitching or decoupling capacitors, or connectors
Select Components
• Press one button and wait for the EMC violations to be listed
Start EMC Rule Check
CST BOARDCHECK: Rules
EMC rules SI rules
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EMC Rule Check Violations
Critical Net Near Edge of Reference Plane
Critical Net Near I/O NetCritical Differential Net Length Matching and Spacing
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Partitioning of the Model / USB Channel
choke to
connector pinsCM
choke
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driver to
choke
CM Signals in Channel
11
22
Source of CM voltage at connector?
1. DM to CM coupling in line
2. coupling via neighbouring line
DM to CM coupling
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frequency in GHz
DM to CM coupling
S21in dB
in line -25 dB
via neighbouring line -55 dB
CM Signals in Channel
Without CM choke With CM choke
11DM DM ��������CMCM
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time in ns
CM voltage in V 1.5 V
80 mV
Driver output skew set to 100ps
Non perfect balanced lice increases skew and CM conversion
Radiated Emissions Prediction (I)
Convolution of impulse response with
Without CM choke63 dBµV/m
Cable
shield
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Convolution of impulse response with
periodic CM noise
3 meter emissions scan
With CM choke34 dBµV/m
System Assembly and Modeling
Chassis
Schematic View Assembly View
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PCB Vented
Panel
Heat sinks
PCB – Near Field Source ModelingPortion of chassis
modeled to capture
reflections
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Chassis EmissionsBaseline Case
Heat sinks
Near field source (automatically
positioned based on PCB location)
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Heat sinks
Included
Heat sink
Clone block
Vented Panel OptimizationVented Panel Plane wave
excitation
Parametric Sweep
Task to determine
optimum hole
dimensions
Chassis including
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Chassis including
Vented Panel Optimized vented panel
positioned behind fans
Vented Panel Optimization
Without Vented Panel With Vented Panel
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Surface Current distribution @ 5GHz
CST BOARDCHECK
• Identify critical nets
Integrated workflows
• PCB + connector + cable
Transient co-simulation
Key Features for Emissions Workflows
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• Broadband response, field/circuit coupling (CM chokes etc.)
Efficient cable and aperture modeling
• CS complex cable bundles, TLM compact aperture models
Simulation of EMC test setup
• External ground plane, far-field probes, cylinder scan
System Assembly and Modeling (SAM)
• System-level simulation of design variants
Typical Susceptibility Issues
1
3
4
x
5
Source Victim
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Power Line (or other interconnecting cables)
235
Failure criteria depends on the testA No degradation in performance, operates as intended at all timesB Degradation allowed during the test, full performance must be restored
following the test, without user interventionC Degradation allowed during the test, and after the test, provided that
full performance can be restored automatically or by user intervention
ESD Generator ModelThe motivation for developing a detailed full
3D model of the generator is to correctly
simulate the asymmetric fields generated by
the discharge and their coupling to the system.
Discharge current
at gun tip
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Full wave model for simulating Noiseken ESD Generator
Dazhao Liu; Nandy, A.; Pommerenke, D.; Soon Jae Kwon;
Ki Hyuk Kim; IEEE Symposium on EMC,17-21 Aug. 2009
Induced voltage in
semi-circular loop
Time animation confirms the asymmetric
field distribution. This may affect the
coupling to the system under test
ESD to Enclosure with Cable EntryExternal Cable
Screen Bonded to
Enclosure
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Bi-Directional co-simulation
between the 3D field, cable
and circuit simulations allows
the effect of cable entry to
be considered
External
Cable Screen
not Bonded
to Enclosure
ESD Transient co-simulation
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Modeling details/ports
Port 1Ports 3,4
(diodes)
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Port 2
(diodes)Reader_p
Reader_n
tag_n
tag_p
Results/currents
Reader_n
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tag_n
Surface current
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Hybrid Cable EMI
Load
SMPS
Sensor
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Programmable switch mode power supply driving an intelligent
sensor with high speed RS485 communications
IGBT switching is used to generate Pulse Width Modulation
waveforms to supply the sensor
Interference between Power and Control circuits
Import measured screen
transfer impedance
RS485
screen
Cable Parameter Extraction
C+,- = 0.0021pF/m
Analysis of mutual
capacitance between Vpos
and Vneg phase wires
Vpos
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C+,- = 0.0021pF/m Vpos
Vneg
CST EMS can used to design cable cross section and extract parasitic values
CST CS uses an internal 2D field solver to extract parasitic values for TL analysis
New curved tetrahedral elements in EMS electrostatic solver
Interference AnalysisCST CS used to investigate CM noise for
different SMPS waveforms, cable
lengths, cable screens and terminations
Cable/circuit co-simulation
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Input SMPS
PWM voltage
CM Current in
RS485 line
Typical E3 Issues
200kA peak
1.5µs rise, 88 µs fall 50 kV/m peak1ns rise, 25 ns fall
I (A) E (V/m)
tt
300 V/m CW field 10 KHz to 40 GHz
EMP
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Lightning Strike Electromagnetic Pulse
Lightning and EMP are transient effects: peak fields and dissipated energy are critical
HIRF requires analysis over an extremely wide spectrum (10 KHz to 40 GHz)
Lightning channel
High Intensity Radiated Fields
HIRF
Field/Cable Co-Sim.Plane Wave Transient EMP
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Simulation of incident EMP and effect of cable shield connection to enclosure
Good cable screen to chassis connection
Poor cable screen to chassis connection
Internal probe
Rotorcraft EMP SimulationFree standing curves for slots/seams
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Huge difference in scale!
500nm ITO thickness vs. airframe dimensions
Rotorcraft EMP Simulation
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ITO coated canopy reduces peak electric field inside cockpit from 8 KV/m to 800 V/m
Solve time 200m on 8-core CPU / 4.3 GB RAM
EMP Protection AssessmentTrue transient co-simulationReal world cable modeling
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Non-linear transient protection
devices modeled by true transient
co-simulation
Solid and braided screens can be
added to cable model to
investigate shielding
Cosite AnalysisPowerful workflows for antenna co-site and RADHAZ analysis
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Near Field Source
� Model exchange thru S-parameter and
touchstone standard
� Fully automated Saber model export
approach in CST Studio Suite
CST STUDIO to Saber Link
Structural Component Model
S-Parameter Computation
CST Studio Suite
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approach in CST Studio Suite
� Easy external model integration in Saber
thru drag & drop
� Full support for transient & frequency
analysis in Saber
Touchstone Exchange Format
S-Parameter Model Block
TR or AC Analysis
CST Studio Suite
Saber
Common Mode Choke Example
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Matching the Inductance
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Typical mue value for the ferrite was chosenNumber of windings was adjusted to match inductance given in datasheet
Fine tuning - Common Mode Impedance
1e5
Wire Resistance
Inter wire capacitance
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1000
2000
Export into Synopsys Saber
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Drag and Drop the created files
into the Saber library.
Frequency Analysis in Saber
Place into Saber
Schematic
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common mode +1V / +1V
differential mode +1V / -1V
Hybrid Cable Example
Load
SMPS
Sensor
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Programmable switch mode power supply driving an intelligent sensor with high speed RS485 communications
Import measured screen
transfer impedance into
CST Cable Studio
RS485
screen
S Parameters for Saber Export
Broadband S parameter output to
cover power harmonic spectrum
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Cable screens groundedPorts placed on power and RS485 pins for coupling analysis
Transient Analysis in Saber
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Place into Saber
Schematic
Export Circuit to Synopsys Saber
In addition to S parameter link, CABLE STUDIO can directly generate an
equivalent circuit model for Saber…
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Equivalent circuit derived from 2D cross section field solver and TL solver
Powerful solutions for analyzing broad range of Emissions Susceptibility and E3problems
� Coupling, shielding, ESD, lightning, EMP, HIRF…
Transient solver� Direct time-domain analysis of transients such as ESD, EMP and lightning
Co-simulation� MWS+CS+DS co-simulation enables coupling between fields, cables and circuits
Conclusions
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� MWS+CS+DS co-simulation enables coupling between fields, cables and circuits
Compact models� Thin conducting panels, slots/gaps, joints/seams and ventilation panels
Realistic cable models� Twisted conductors, screens, connections to 3D structure
New links between CST STUDIO SUITE and Synopsys Saber providesmooth workflow for system-level analysis