EMC Back to Basics
Matthew Carter
EMC Product Support Engineer
Agilent Technologies Inc.
April 16, 2014
© Agilent Technologies, Inc. 2014
Agenda – EMC Back to Basics
• Overview
• What is Electromagnetic Compatibility?
• Which equipment?
• Pre-compliance vs. Compliance
• Which standards?
• EMI Receiver Architecture
• Specifications: Which are important and why?
• Making an Emissions Measurement
• Other equipment considerations
• Q&A
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Sources of Electromagnetic Interference
•Natural Sources
-Lightning
-Sun Spots
•Unintentional emitting products
-Power lines
-Motors (mixers, hair dryers etc)
-Lighting, appliances
•Devices that intentionally emit signals
-Most computers
-Hand held communication devices
-Radar, transceivers, broadcast equipment etc
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Basic Definitions
Electromagnetic Compatibility (EMC):
The ability for electrical devices to operating in the same environment
without interfering with one another
Electromagnetic Interference (EMI):
Electromagnetic energy emissions from one device causing reduced or
degraded performance in another device
Electromagnetic Compliance
A product is considered to be in Electromagnetic Compliance when it
meets all applicable electromagnetic regulations.
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EMC Market Overview
Global market, mandatory regulation
− Vendors test in order to be able to sell their products
– Electronic “Smog testing”
Commercial Standards determined
by International Committee
− Slow moving, political
Adaptive
− Adapt techniques and measurements
to meet the needs of rapidly changing products
– Eg: IT, Cellular, Wireless, Multimedia
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EMC Market Segmentation
Measurement
Type:
Application:
Sub-segments:
Emissions
Immunity
Radiated & Conducted
Radiated & Conducted
- Compliance
- Pre-Compliance
Compliance
Commercial
Military
- Product Type
- Product Class
- Country
-
.
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Definitions: Emissions, Susceptibility, Immunity
Radiated
Emissions
Radiated
Susceptibility
(or Immunity)
Conducted
Emissions
Conducted
Susceptibility
(or Immunity)
EMC Back to Basics 2014
Measurement Equipment – Emissions
Radiated
Emissions
EUT
EUT
transducer
Conducted
Emissions
Mains
Equipment
Compliance receivers
Spectrum Analyzers
Preamps
Antennas
Measurement SW
Towers
Turntables
Control SW
Artificial Mains Networks
LISN (line impedance stabilization network)
Conducted Transducers
Measurement SW
Open Sites
Anechoic Chambers
Semi-Anechoic Chambers
TEM cells
Reverberation chambers
EMC Back to Basics 2014
Compliance vs. Precompliance Measurements
Full Compliance
- Pass/Fail final regulatory testing
- Requires specific equipment and test site
-
must comply to specific Mil or Comm’l standards
MXE
- Expensive and time consuming
Precompliance Measurements
- “Unofficial” performance estimate done prior
to Full Compliance test
- Typically done with SA on available location
X-Series w/
N6141A
- Purpose is to minimize chance of failure at
Compliance test.
EMC Back to Basics 2014
Radiated
Immunity
~
EUT
Conducted
Immunity
EUT
~
transducer
ESD source
Measurement Equipment – Immunity
AMN
transducer
Equipment
RF Sources
Power meters
Power amps
Antennas
Measurement SW
Control SW
LISN
Coupling Transducers
- clamps, etc.
ESD sources
Screen rooms
TEM cells
GTEM cells
EMC Back to Basics 2014
Segmentation
Measurement
Type:
Application:
Sub-segments:
Emissions
Immunity
Radiated & Conducted
Radiated & Conducted
- Compliance
- Pre-Compliance
Compliance
Commercial
Military
- Product Type
- Product Class
- Country
-
.
EMC Back to Basics 2014
CISPR Recommends Commercial Limits,
Measuring Equipment and Methodologies
CISPR (Special International Committee on Radio Interference)
• a sub committee of the IEC (International Electrotechnical Commission)
• determines and recommends required emissions and immunity:
- limits for products sold in the worldwide commercial
market
- test equipment requirements
- test procedures/methodologies
EMC Back to Basics 2014
CISPR Product Groups
CISPR 11 - Industrial, Scientific, and Medical (ISM) Radio-Frequency Equipment
CISPR 12 - Vehicles, Motorboats, and Spark-Ignited Engine-Driven Devices
CISPR 13 - Sound and Television Broadcast Receivers and Associated Equipment
CISPR 14 - Household Appliances, Electric Tools, and Similar Apparatus
CISPR 15 - Electrical Lighting and Similar Equipment.
CISPR 17 - Suppression Characteristics of Passive Radio Interference Filters and
Suppression Components.
CISPR 18 - Overhead Power Lines and High-Voltage Equipment
CISPR 20 - Sound and Television Broadcast Receivers and Associated Equipment
CISPR 21 - Interference to Mobile Radio communications
CISPR 22 - Information Technology Equipment–Radio Disturbance Characteristics
CISPR 24 - Information Technology Equipment–Immunity Characteristics
CISPR 25 - Receivers Used on Board Vehicles, Boats, and on
CISPR 32 – Multimedia devices emission testing (under development)
CISPR 35 – Multimedia devices immunity testing (under development)
EMC Back to Basics 2014
Commercial requirements for EMI receivers
• What is CISPR 16-1-1 ?
Specifies the characteristics and performance of equipment
for the measurement of radio disturbance in the frequency
range 9 kHz to 18 GHz for commercial devices.
• CISPR 16 Equipment Requirements
•
•
•
•
•
•
Detectors (Peak, Quasi-peak, EMI-avg, etc)
Reference BW (aka. RBW filter)
Amplitude Accuracy
Input Impedance
Ability to pass the CISPR pulse test
And more…
EMC Back to Basics 2014
Commercial Regulations
IEC/CISPR
Measurement Std. – CISPR 16
Equipment Std. – CISPR 16
Product Std. - CISPR 11-15, etc.
IEC 61XXX
GB
VCCI
ANSI
FCC
CENELEC
EN
EMC Back to Basics 2014
Commercial EMC Standards - Examples
Country
/Organization
Entity
Standards
US
FCC, DoD
FCC Part xx, MIL-STD. xxx
IEC
CISPR
CISPR Pub. xx
IEC
TC77
IEC 6xxxx
EC
CENELEC
EN 550xx
CSA
ICES xxx
AS/NZS
AS/NZS CISPR xx
VCCI
J550xx
CCC, MoD
GB xxxx- xxxx
GJB xxx- xx (equivalent to Mil-STD)
Korea
MIC
Equivalent to EN 550xx
Taiwan
BSMI
CNS xxxx
Canada
Australia/NZ
Japan
China
(Mainland)
EMC Back to Basics 2014
Segmentation
Measurement
Type:
Application:
Sub-segments:
Emissions
Immunity
Radiated & Conducted
Radiated & Conducted
- Compliance
- Pre-Compliance
Compliance
Commercial
Military
- Product Type
- Product Class
- Country
-
.
EMC Back to Basics 2014
Country-Specific Military Regulations
Tend to be based on
US MIL STD 461…..
Current version: 461F (2007)
… but many include unique
emissions and immunity tests
EMC Back to Basics 2014
MIL-STD 461 Receiver Requirements
• U.S. military standard
• Published by the Department of Defense
• MIL-STD-461 Section 4.3.10
• Receiver Requirements
• Peak detector
• Sensitivity
• Amplitude accuracy
• Frequency accuracy
• Specified dwell times
EMC Back to Basics 2014
Agenda – EMC Back to Basics
• Overview
• EMI Receiver Architecture
• Specifications: Which are important and why?
• Making an Emissions Measurement
• Other equipment considerations
• Q&A
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EMI Receiver Block Diagram
Pre-amp
Input 2
MXE
Transient
Limiter
Attenuation
Input 1
RF Preselector
Digital IF
Filter
Digital Detectors
FFT
Analog IF
Filter
Swept vs . FFT
Digital Log Amp
ADC
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RF Preselector Bands
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RF Pre-selection (RF input filtering)
 Purpose of RF pre-selection
• Help to prevent overload by reducing total energy at input mixer
• RF preselector tracks the center frequency of the EMI receiver
• The bandwidth of the RF preselector is wider than the widest RBW used
 Useful in measuring broadband signals
 Types of filters used in RF pre-selectors
•
Low-pass, Band-pass and High-pass
•
Fixed and Tracking
Narrow
band
signals
Broadband
signals
RF Preselector
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EMI Receiver Block Diagram
Pre-amp
Input 2
MXE
Transient
Limiter
Attenuation
Input 1
RF Preselector
Digital IF
Filter
Digital Detectors
FFT
Analog IF
Filter
Swept vs . FFT
Digital Log Amp
ADC
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Methods to EMI Scanning
• Stepped Scan
• Slowest method
• LO moves for every bin
• Must re-tune LO each time
• Swept Scan
• Slow (slightly faster than Stepped)
• LO re-tunes once each sweep
FFT
• Time Domain Scan (TDS)
• Very fast
• Highly overlapped FFT (>90%)
• Alternate scan method allowed by CISPR 16
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How Time Domain Sweep Saves Time
Only have to dwell for each
FFT BW (multiple RBWs)
Have to dwell at
each RBW
Receiver
FFT BW
amplitude
amplitude
Receiver
Resolution BW
frequency
Swept or Stepped
Frequency Scan
frequency
Time Domain
Frequency Scan
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Agenda – EMC Back to Basics
• Overview
• EMI Receiver Architecture
• Specifications: Which are important and why?
• Making an Emissions Measurement
• Other equipment considerations
• Q&A
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Specifications?
A Definition
Specifications describe the performance of parameters covered by the product
warranty (temperature = 5 to 55°C, unless otherwise noted).
Typical values describe additional product performance information that is not
covered by the product warranty. It is performance beyond specification that 80
% of the units exhibit with a 95 % confidence level over the temperature range
20 to 30° C. Typical performance does not include measurement uncertainty.
Nominal values indicate expected performance, or describe product
performance that is useful in the application of the product, but is not covered by
the product warranty.
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Key Specifications for EMI
• Sensitivity
• Amplitude Accuracy
• Scan Speed
• Others?
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Specifications: Sensitivity/DANL
Sensitivity is the Smallest Signal That Can Be
Measured
Signal
Equals
Noise
2.2 dB
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Specifications: Sensitivity/DANL
Effective Level of Displayed Noise is a Function
of RF Input Attenuation
signal level
10 dB
Attenuation = 10 dB
Attenuation = 20 dB
Signal To Noise Ratio Decreases as
RF Input Attenuation is Increased
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Sensitivity/DANL: IF Filter (RBW)
Displayed Noise is a Function of IF Filter
Bandwidth
100 kHz RBW
10 dB
10 kHz RBW
10 dB
1 kHz RBW
Decreased BW = Decreased Noise
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Sensitivity/DANL: Summary
For Best Sensitivity Use:

Narrowest Resolution BW allowed

Minimum RF Input Attenuation

Sufficient Averaging (video or trace - if allowed)

Using the Preamp also improves sensitivity

Noise Floor Extension
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Specifications: Amplitude Accuracy
Components which contribute to uncertainty are:
• Input mismatch (VSWR)
• RF Input attenuator (Atten. switching uncertainty)
• Mixer and input filter (frequency response)
• IF gain/attenuation (reference level accuracy)
• RBW filters (RBW switching uncertainty)
• Log amp (display scale fidelity)
• Calibrator (amplitude accuracy)
FFT
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Digital IF Improves Amplitude Accuracy
Input
Connector
RF Input
Attenuator
2 dB Steps
Pre-selector
Downconversion
DSP
ADC
Frequency
Dependent
Frequency
Independent
Digital IF improves Amplitude Accuracy:
•
Input connector (mismatch)
•
Calibrator
•
RF input attenuator
−
•
Ref Level switching uncertainty (IF gain)
− Level correction digitally synthesized
•
flatness and switching
Mixer and input filter
−
•
RBW filter switching uncertainty
− RBWs all digitally synthesized
•
frequency response
Display scale fidelity (Log Amp)
− Log response & display scaling digitally
synthesized
IF
Filter
IF
Gain
Log
Amp
Log
Video
Filter
ADC
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Digital IF Improves Amplitude Accuracy
Input
Connector
RF Input
Attenuator
2 dB Steps
Pre-selector
Downconversion
DSP
ADC
Frequency
Dependent
Amplitude
Uncertainty
N9038A
Receiver
(older receivers)
Ref Level
Switching
0dB
<= +/- 1dB
RBW
Switching
+/- .05dB
<= +/- .5dB
Display Scale
Fidelity
+/- .15dB
Analog IF
Frequency
Independent
Digital IF improves Amplitude Accuracy:
•
Ref Level switching uncertainty (IF gain)
− Level correction digitally synthesized
•
RBW filter switching uncertainty
− RBWs all digitally synthesized
<= +/- .85dB
•
Display scale fidelity (Log Amp)
− Log response & display scaling digitally
synthesized
IF
Filter
IF
Gain
Log
Amp
Log
Video
Filter
ADC
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Specifications: Scan Speed
• Need for SPEED
– DUTs that require short measurement time (ex. motor starter)
– Test MORE devices
– Shorter turn-around-time
• Depends On:
– Scan type (Stepped, Swept, Time Domain)
– Resolution Bandwidth
– Dwell Time
– RF Preselector
– Other?
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Agenda – EMC Back to Basics
• Overview
• EMI Receiver Architecture
• Specifications: Which are important and why?
• Making an Emissions Measurement
• Other equipment considerations
• Q&A
EMC Back to Basics 2014
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Making an emissions measurement
• Recommended by CISPR
Pre-scan
• Measurement methodology
found in CISPR 16-2-3
• Fastest way to make the
measurement
• MIL Measurements*
Data Reduction
Maximization
Final Measurement
Report Generation
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Pre-Scan
•
Preview spectrum
using “Peak” detector
•
Measurement Parameters
•
–
Frequency range
–
Limit lines
–
Margins
–
Antenna Factors
–
Scan Type
Prescan
Scan Types
–
Stepped
–
Swept
–
Time Domain
Pre-scan
Data Reduction
Maximization
Final
Measurement
Report
Generation
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Data Reduction
•
•
Signals exceeding the
limit are automatically:
–
Marked in red
–
Peaks are marked with
white “X”
–
Added to signal list
Only do final
measurement on
signals exceeding the
limit and margin
–
Don’t measure
unnecessary signals
–
Saves time
Pre-scan
Data Reduction
Signal List
Maximization
Final
Measurement
Report
Generation
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Maximization Techniques
Maximize signal amplitude before final measurement
Receiver mode
Spectrum Analyzer Mode
•
Monitor Spectrum
–
Simultaneous spectrum and meter
measurements
–
Access to signal (suspect) list
–
Meter max hold
Pre-scan
Data Reduction
Maximization
•
Spectrum Analyzer mode
–
Switch between EMI receiver and SA
modes using global center frequency
–
Powerful analyzer mode
Final
Measurement
Report
Generation
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Final Measurement
• Signals in list are
automatically
measured
• Measure suspect signals
with Quasi-peak, EMI
average detector, etc.
• Suspect signals still
failing? Start
troubleshooting?
Pre-scan
Data Reduction
Maximization
Final
Measurement
Report
Generation
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Report Generation
•
Report Generator
–
Settings
–
Screenshots
–
Tables
Pre-scan
Data Reduction
Report Format: PDF or HTML
Maximization
Final
Measurement
Report
Generation
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Agenda – EMC Back to Basics
• Overview
• EMI Receiver Architecture
• Specifications: Which are important and why?
• Making an Emissions Measurement
• Other equipment considerations
• Q&A
EMC Back to Basics 2014
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Transducers for EMI measurements
“a device that receives a signal in the form of one type of energy
and converts it to a signal in another form”
-dictionary.com
• Near Field Probe
• Near Field Scanner
• Line Impedance Stabilization Network (LISN)
• Antennas
• Other devices?
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Near Field Probes – E & H Field
• Use Cases
– Pre-compliance
– Diagnostics
• Characteristics
E Field Probe
– Frequency Range
– Spatial Resolution
– Sensitivity
• Measure or Generate Fields
– Emissions or Susceptibility
H Field Probe
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Near Field Scanners
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LISN: Line Impedance Stabilization Network
• Typically used for conducted emission measurements
• Isolates the power mains from the EUT
• Isolates EUT from the power mains
• Powers the EUT and couples signals to EMI receiver
No Transient
Limiter Required
Power Mains
Types of LISNs
• V-LISN
MXE Receiver
EUT
• Delta LISN
LISN
• T-LISN
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EMI Broadband Antenna Examples
Double ridged horn
Log Periodic
Hybrid Log Periodic
Biconical
Hybrid Log Periodic
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Understanding Antenna Factors
“Ratio of the electric field to the
voltage out of the antenna”
Linear Units
𝐸𝑖𝑛
AF =
𝑉𝑜𝑢𝑡
AF = Antenna Factor (1/m)
E = Electric Field units (V/m)
V = Voltage output from antenna (V)
Log Units
Antenna Factor (dB/m)
Typical biconical antenna factors
20
10
20
150
Frequency (MHz)
300
AF(dB/m) = E(dBµV/m) –V(dBµV)
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Antenna Factors on a Typical Display
Corrected
for a
broadband
antenna
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Examples of Test Facilities
5 Meter Semi Anechoic* Chamber
(Located on the Agilent Santa Rosa site)
This chamber uses 2 antenna
towers, one for vertical and
one for horizontal polarization.
Origin
Anechoic
an- “not” + echoic (echo)
*Anechoic material is made
of carbon impregnated
rubberized cones or ferrite
tiles or both
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Examples of Test Facilities
Open Area Test Site (OATS)
• Useful in low ambient signal
environments
Reverberation Chamber
• Uses a mode stirring tuner to
generate a uniform field (no
absorption material on the walls)
GHz Transverse Electro Magnetic Cell
(GTEM Cell)
• Used for smaller devices. Can be
used for immunity and emissions.
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Automation Software
Reasons for Automation
-Supplement skill and knowledge of the tester
-Measurements repeatability
-Results are presented in a common format
-Reduce test time by automating setups
-Run turntables and antenna towers
Types of Automation
-Internally executed application such as N6141A EMI Application
-PC based applications
Software Available
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Automation Software
Receiver
Control
Room
• Automation software typically
communicates with the receiver
over LAN or GPIB
Chamber
• Uses SCPI commands
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Questions?
Please type them in the chat box now
N9038A MXE EMI Receiver
www.agilent.com/find/mxe
X-Series Signal/Spectrum Analyzers
www.agilent.com/find/x-series
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