This three-day course is designed for technicians, operators, and engineers who need an understanding of all facets of grounding and shielding at the circuit, PCB, box or equipment level, cable-interconnected boxes (subsystem), system and building, facilities or vehicle levels. The course offers a discussion of the qualitative techniques for EMI control through grounding and shielding at all levels. It provides for selection of EMI suppression methods via math modeling and graphics of grounding and shielding parameters. Our instructor will use computer software to provide real world examples and case histories. The computer software simulates and demonstrates various concepts and helps bridge the gap between theory and the real world. The computer software will be made available to the attendees. One of the computer programs is used to design interconnecting equipments. This program demonstrates the impact of various grounding schemes and different "fixes" that are applied. Another computer program is used to design a shielded enclosure. The program considers the box material; seams and gaskets; cooling and viewing apertures; and various "fixes" that may be used for aperture protection. . There are also hardware demonstrations of the effect of various compromises and resulting "fixes" on the shielding effectiveness of an enclosure. The compromises that are demonstrated are seam leakage, and a conductor penetrating the enclosure. The hardware demonstrations also include incorporating various "fixes" and illustrating their impact.

1. Professional Development Short Course On:
Grounding and Shielding for EMC
Instructor:
Dr. William G. Duff (Bill)
ATI Course Schedule: http://www.ATIcourses.com/schedule.htm
http://www.aticourses.com/intro_to_grounding_shielding.htm
ATI's Grounding and Shielding for EMC:

2. www.ATIcourses.com
Boost Your Skills 349 Berkshire Drive
Riva, Maryland 21140
with On-Site Courses Telephone 1-888-501-2100 / (410) 965-8805
Tailored to Your Needs
Fax (410) 956-5785
Email: ATI@ATIcourses.com
The Applied Technology Institute specializes in training programs for technical professionals. Our courses keep you
current in the state-of-the-art technology that is essential to keep your company on the cutting edge in today’s highly
competitive marketplace. Since 1984, ATI has earned the trust of training departments nationwide, and has presented
on-site training at the major Navy, Air Force and NASA centers, and for a large number of contractors. Our training
increases effectiveness and productivity. Learn from the proven best.
For a Free On-Site Quote Visit Us At: http://www.ATIcourses.com/free_onsite_quote.asp
For Our Current Public Course Schedule Go To: http://www.ATIcourses.com/schedule.htm

3. What Is Ground?
• Earth Ground
• Power Ground
• Signal ground
• Safety Ground
• Return
• Reference Level

4. Ground Means any Reference
Conductor Used for a Common Return

5. Grounding Misuse and Myths
• Reasons for Grounding Are Not Clear
• The Word "Grounding" is Often Misused
when other Words are Meant, such as:
Connect to Bonding
Return Path Earthing
• Many Myths Exist, such as:
"Lower Impedance is Always Better"
"Use Grounds for Digital-Circuit Reference"
"Use Separate Safety, Instrument & System Gnd.
• Reasons for Grounding Are Not Clear

6. Grounding for EMC
• Ground Circuits, Equipments, Systems,
Cables, Shields
• Common Mode and Differential Mode
Coupling
• Avoid Ground Loops
• More Grounds are not Better

7. Interconnected Equipment Having 29
Questions = 229 = 500,000,000 Answers

8. Effects of Shared Ground
Impedance
• Common Source or Common Ground
Impedance Coupling
• EMI and signal use same impedance
• Shared impedance provides path for
EMI to couple from a source to a victim.
• Minimizing the shared ground
impedane will help mitigate the
problem.
• A single point ground may help.

9. Common Ground Impedance Common Mode EMI
CMC
Power Source Load
CMC
EMI EMI'
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
Metallic Structure
Figure 10. Common Ground Impedence Common Mode EMI

10. Illustration of Common Mode Currents
CMC 1
Power Source Load
CMC 2
CMC
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
Metallic Structure
Figure 4. Illustration of Common Mode Currents

11. Illustration of Differential Mode Currents
DCM1
Power Source Load
DCM2
Figure 3. Illustration of Differential Mode Currents

12. Illustration of Common and Differential Mode Currents
CMC 1 DMC 1
Power Source Load
CMC 2 DMC 2
CMC
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
Metallic Structure
Figure 5. Illustration of Common and Differential Mode Currents
Illustration of Common and Differential Mode Currents
Illustration of Common and Differential Mode Currents

13. PRINCIPAL RADIATION SOURCES ON
PRINTED CIRCUIT BOARD
Radiation from
IC dips
Logic families
clock rates
• Large single-layer board
• PCB card cage with back plane
• Multi-layer board
Radiation from
ribbon cables

14. Common Mode Radiated EMI
Radiated EMI
CMC 1
Power Source Load
CMC 2
CMC
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
Metallic Structure
Figure 11. Common Mode Radiated EMI

16. Ground-Loop Coupling
Converts Common Mode Voltage
to Differential-Mode Voltage

17. Using Ferrites to Absorb
Common-Mode EMI

18. Added Feed-Thru Capacitors -
Help Reduce ESD and RF Susceptibility
Note: Max
Cap Value
Must
Support
Data
Bandwidth
C < 1/ωR

19. Coupling Rejection Offered by
Twisting Wire Pair

20. SHIELDING APPLIES TO ALL LEVELS
• Components • Systems
• Circuits • Cables
• Functional Stages • Platforms
• Equipments • Buildings

21. CONCEPTUAL ILLUSTRATION OF FIELD INTENSITIES VS.
SOURCE TYPE AND DISTANCE
High Current Corresponds to Low Current Corresponds to
Low Impedance High Impedance
High E Low E
Monopole Eθ Eθ
Loop
Hθ
Low H I High H Hθ
V
Near Far Near Far
Field Field V Field Field
High-Impedance Source Low - Impedance,
Electric-Field Source and Wave Magnetic - Field Source and Wave

22. FIELD IMPEDANCE AS A FUNCTION OF DISTANCE FROM
SOURCE

23. ELECTRIC FIELD VS SOURCE DISTANCE

24. SUMMARY
Near Field Far Field
Electric Fields Plane Waves
Are Generated for all
Z > 377 Ohms
Radiated From High Source Impedances for
Impedance Sources Distance Greater Than
Magnetic Fields Approximately
1/6 of a Wavelength
Z < 377 Ohms
Radiated from Low
Impedance Sources

25. REPRESENTATION OF SHIELDING PHENOMENA
FOR PLANE WAVES
Ey Inside of Enclosure
Hz
Incident WaveA Ey Transmitted Wave
Ey
B
H
Ey Attenuated
Hz Incident
Hz
Ey Hz
Reflected Wave
Wave Internal Reflecting
Outside World Metal Wave
Barrier

26. SHIELDING EFFECTIVENESS (SE)
SEdB = 20 log10(Eoutside/Einside)
SEdB = 20 log10(Houtside/Hinside)
where: E = Electric-field Strength
H = Magnetic-field Strength
SEdB = RdB + AdB
where:
RdB = Reflection Loss in dB
AdB = Absorption Loss in dB

27. REFLECTION LOSS
( K + 1)2 ZW
RdB = 20 log10 ,K = VSWR
4K Zb
 Zw 
≅ 20 log10  , K ≥ 10
 4 Zb 
Where :
E
Zw = wave impedance =
H
jω μ jω μ
Zb = barrier impedance = =
σ + jω ε σ
for ω ε < < σ

28. REFLECTION LOSS (RdB) OF PLANE WAVES VS FREQUENCY
3kHz 30kHz 300kHz 3MHz 30MHz 300MHz
200
200
150 150
Copper
100 100
Iron*
50 Hypernick* 50
0
1kHz 10kHz 100kHz 1MHz 10MHz 100MHz 0
Radio Frequency
Valid for thickness > 3 δ
δ = Skin Depth * Permeability assumed constant with frequency

29. ABSORPTION LOSS, A
Current Density
0.066
δ= mm
f MHz μ r σ r
δ
t
AdB = 8.68 t / δ = 131 t f MHz μ r σ r
where t = thickness in mm
f MHz = frequency in MHz
μ r = permeability relative to copper
σ r = conductivity relative to copper

30. ABSORPTION LOSS VS FREQUENCY

31. PRINCIPAL BOX SHIELDING COMPROMISES
Holes or Slots Screw Spacing
Cover Plate for Convection Cooling = Slot Radiation
for Access
Status
Indicator
Lamp
Forced Air
Cooling
Panel Meter
Potentiometer
Connectors
Fuse
Switch

32. SLOT AND APERTURE LEAKAGE
L
t
h

t << h Shield Material
SE (dB)
•

Log Frequency •λ / 2

33. Reducing Radiation Coupling
by Shielding Cable Wires

34. To learn more please attend ATI course
Grounding and Shielding for EMC
Please post your comments and questions to our blog:
http://www.aticourses.com/blog/
Sign-up for ATI's monthly Course Schedule Updates :
http://www.aticourses.com/email_signup_page.html