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Forum De L’Electronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de l’électronique 2006 David P. Johns (Flomerics Inc) Yannis Braux (Flomerics
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Page 1: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum De L’Electronique 2006

Taking the Guesswork out of EMC/EMI Design!

Flomerics

Forum de l’électronique 2006

David P. Johns (Flomerics Inc)

Yannis Braux (Flomerics France)

Page 2: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

EMC Design

• EMC/EMI Design has been far from an exact science.

• Engineers have not been able to say:– “Do it like this and it will work…”.

• Instead, Engineers have said: – “Do it like this and it may work”,

– or,

– “This is more likely to work, but at a higher cost!”

• Considerable guesswork is involved.

Page 3: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

EMC Design

• EMC/EMI Design is a moving target!• The EM environment is flooding:

– proliferation of wireless communications devices – products emitting higher frequencies (faster switching)

• Below GHz, Radiated Emissions launch mechanisms are relatively well understood

• Above GHz…a different story!• Design rules that worked in the past may not

work in the future.

Page 4: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

EMC Design

• EM Design tools have matured considerably over the last 5 years

• Tremendous opportunity for EMC/EMI Engineers to:– work more effectively with greater confidence– identify problems earlier in Design– Be more definite and accurate in their

recommendations– minimize the test, fix, re-test cycle– pass compliance and enter the market quicker

Page 5: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

SE: EMC Corp Test Box

Vertical slots

(1.5 x 0.25 in.)

Horizontal slots

(1.5 x 0.25 in.)

Overlapping Lid

(1cm overlap)

Corner seams

(4 in. x 10 mil)

Aluminum Box

(6 x 6 x 4 in.)

Noise Source

(106.25 MHz clock)

Page 6: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

FLO/EMC Simulation Model

Wire loops combined with monopole for noise source

Shapes assigned electrical properties of air to model large apertures

Equivalent model for air-vent (perforated plate)

Seams drawn on enclosure

Page 7: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

3D TLM Analysis

Large apertures are meshed

Seams are sub-cell

Wires and circuits are sub-cell

Fine cells are recombined away from geometry – reduces cell count from 412k to 60k

Grid uses graded density mesh

E and H fields calculated in each cell

Page 8: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

From Time to Frequency

Impulse Response Frequency Response

Fourier Transform applied to Impulse Response…

Page 9: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Emissions Cylinder Scans

Vertical Polarization

Horizontal Polarization

Emissions vary with angle around the box

SE calculation must take this into account

Page 10: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Delta Test for SE

SE (dB) = E REF (dB) – ESHIELDED (dB)

Page 11: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

SE of EMC Test Box

Page 12: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Surface Current

530 MHz 954 MHz

Page 13: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Surface Current

1590 MHz 1590 MHz1908 MHz

Page 14: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Guesswork Design

• Try closing the 8 horizontal slots to improve the shielding…

• It may work!

Page 15: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

SE with Apertures Taped

Page 16: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Electromagnetic Interference - EMI

• NATO definition;– “An electromagnetic

disturbance which interrupts, obstructs, or otherwise degrades the effective performance of electronic or electrical equipment”

Page 17: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Sources of EMI

1 KHz 1 MHz 10 MHz

100 MHz

1 GHz 10 GHz 100 GHz

Lightning

Nuclear EMP

HIRF

Radar

Digital Electronics

Page 18: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Lightning Analysis

• MIL-STD-464 defines a current component A that represents a severe lightning stroke

• The component can be modeled by a double exponential waveform

• TLM is a time-domain technique and the lightning waveform can be applied as a transient source i(t) = Io(e-t/ – e-t/)

Io = 218,810 A = 88.07 s =1.545 s

Page 19: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Current Diffusion

• Lightning is a low-frequency phenomenon (1 Hz to 10 MHz)

• At low frequencies, metals are not good magnetic shields;– Consider an Aluminum

panel of thickness 1.2mm– Current will diffuse

through the metal according to the skin depth

Page 20: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Lightning Test Problem

• 13.2m sized metal box with interchangeable lid and front panel;– Side walls are perfect

electrical conductors (PEC)

– Top can be PEC or 1.2mm thick Aluminum

– Front panel can be closed or contain a slot

– Lightning current driven into conductor

– Magnetic field calculated inside the box

Lightning conductor

Slot aperture (12 x 0.01)

PML

M. Sarto, IEEE trans. On EMC, Vol. 43, No. 3, August 2001

Page 21: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Simulated Magnetic Field

Diffusion through walls slows responseLightning waveform (source)

Hz

Hx

Hy

Current in conductor Al box

Page 22: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Simulated Magnetic Field

Faster response with slot presentMagnetic field reduced with PEC side walls

Hz

Hx

HyHz

Hx

Hy

PEC side walls, Al lid PEC side walls, Al lid, slotted front panel

Page 23: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Current Distribution

100 KHz

10 MHz

Diffusion dominates Slot leakage dominates

Page 24: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Electromagnetic Pulse (EMP)

• Gamma rays from a nuclear burst collide with air molecules producing Compton electrons

• The Compton electrons interact with the earth's magnetic field, producing an intense electromagnetic pulse (EMP) that propagates downward to the earth's surface

• If a weapon were to be detonated 250 miles above the US, nearly the entire nation would be affected

• Peak electric fields can reach tens of thousands of volts per meter

Page 25: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

EMP Analysis

• MIL-STD-464 defines an Electric field transient that represents a high altitude EMP (HEMP)

• Transient is modeled by a double exponential waveform

• EMP spectrum ranges from 1 MHz to 1 GHz

E(t) = k Eo(e-t/ – e-t/)Eo = 50,000 V/mK = 1.3 = 25 nS = 1.67 nS

Page 26: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

EMP Test Problem

Carbon fiber reinforced front panel

Incident EMP wave 50 KV/m, 5ns rise time and 200ns fall time

70cm size box

Page 27: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

H Field Simulation & Test Results

TLM prediction measured

M. D’Amore et. al, IEEE trans. On EMC, Vol. 42, No. 1, February 2000

Page 28: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

E Field Simulation & Test Results

TLM prediction measured

Page 29: Forum De LElectronique 2006 Taking the Guesswork out of EMC/EMI Design! Flomerics Forum de lélectronique 2006 David P. Johns (Flomerics Inc) Yannis Braux.

Forum de l’électronique 2006

Summary

• EM Simulation has come a long way over the last 5 years

• Simulation enables EMC/EMI Engineers to be more scientific in their approach to Design

• Analysis helps Engineers justify Design changes

• Engineers can Design with greater confidence and certainty

Many thanks to Boris Shusterman and EMC Corp for contributing applications and test results to the presentation…


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