1. Electromagnetic Interference (EMI)
Eric Mitchell
Phil Zanotti
Kasra Dabiran
Leon Voskov
Ross Schwarz

2. Overview Introduction Examples Prevention and Mitigations Techniques
Wireless Devices
Natural Interferences
Switching Circuits
Radio Frequency
Electromagnetic warfare
Prevention and Mitigations Techniques
Standards and Regulations
Summary

3. Background
What is EMI?
Electromagnetic Interference is disturbance that affects an electrical circuit
Caused by induction or outside radiation
Can temporary and permanently disrupt circuit components
Big design issue for new products

4. How does EMI work? Causes Effects
Electric fields radiating from currents
Switching circuits, clocks, natural fields, ect.
Coupling of electric fields into circuits and components
Unintentional and intentional
Effects
Causes problems for electronics
Loss and disruption of data
Growing problem with more advanced devices

5. Examples of EMI

6. Solar Interference 2012 Solar Maximum Solar Storm of 1859
11 year solar cycles
Flight routes over north pole changed
Solar Storm of 1859
March 1989 Solar Storm
X-class solar flare
Power outage in Quebec
Communications with some satellites disrupted for hours
Other potential issues
Spacecraft communication
Induced currents on underground piping
HF radio interference

7. Interference at 2.4 GHz Why use 2.4GHz?
Part of the ISM Band
No license needed to design devices in this range
FCC originally designated GHz band for microwave ovens
Devices and protocols that operate in this band
Cordless telephones
Baby monitors
Bluetooth
Wi-Fi b and g wireless devices (most routers)
Wireless cameras and controllers

8. Cellular Device Interference
Airplanes
No proven scientific basis for banning cell phone use on airplanes
FAA, FCC, and aircraft OEMs are unwilling to spend money to do testing
Ban on cell phone use errs on the side of caution
Medical Equipment
2007 Mayo Clinic study showed that phones have no negative effect on medical equipment
FDA has developed standards for pacemaker OEMs to ensure safety

9. Power Converters Capacitive, Inductive, and Resistive loads
Caused by sudden load changes
Found in many household items
Computers, phone chargers, TVs, etc.
Minimal or no EMI effect created

10. Electromagnetic Pulse
Intense surge of electromagnetic radiation
Created using high-energy explosion (i.e. nuclear)
Gamma rays trap high-energy electrons in earth’s magnetic field
Destroys all power electronics connected to affected power grid

11. Radio Frequency Interference
Two way transmitters, radio stations, amateur radio broadcast
Interrupted signal before reaching receiver
Results in signal masking and distortion

12. Prevention and Mitigation

13. EMI Filters and Chokes Coil of wire wound around magnetic core
Blocks high-frequency AC in a circuit
Passive inductor
Impedance is proportional to frequency
Simple and inexpensive
Energy
Reflected back up the cable
Absorbed resistively within ferrite core (heat)
Audio vs. Radio

14. Electromagnetic Shielding
Shields
Examples
Enclosure formed by conducting material
Isolates electrical devices and blocks external electric fields
Often known as Faraday Cage (invented in 1836)
Amount of reduction depends
Material and its thickness
Size of shielded volume
Frequency of fields
Cables
MRI scan room
Microwave oven
Electronic devices

15. Mitigation Software and Techniques
EMI Analyst is a tool used for meeting EMI requirements set by regulatory agencies
Combines all four areas of EMI analysis
Conducted Emissions
Radiated Emissions
Conducted Susceptibility
Radiated Susceptibility
Money Saving Tool
Reduction of circuit design area

16. Final Emissions Screenshot

17. Standards and Regulations

18. EMI Testing Procedure

19. Regulation Committees
FCC
CISPR
Federal Communications Commission
United States
Modems, Printers, and other I/O devices
The International Special Committee on Radio Frequency Interference
International
House hold appliances, Ignition systems, fluorescent lamps

20. Classes of Regulations
Class A
Class B
“A computing device that is marketed for use in a commercial, industrial, or business environment; exclusive of a device which is marketed for use by the general public, or which is intended to be used in the home.”
“A computing device that is marketed for use in a residential environment notwithstanding use in a commercial, business, and environmental environments.”

21. FCC and CISPR Class A

22. FCC and CISPR Class B

23. Other types of standards
MIL-STD-416D
CE - Conformité Européenne
Department of Defense
Even harder-to-meet standards than FCC and CISPR
Dependent on reliability of electronic and communication equipment
European Conformity
Identifies that a product or machine is compliant with all safety requirements
Requirement not a voluntary process

24. Conclusion Introduction and Background
Examples of Electromagnetic Interference
Prevention and Mitigation Techniques
Laws and Regulations
Questions?