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EMC Back to Basics
Matthew Carter
EMC Product Support Engineer
Agilent Technologies Inc.
April 16, 2014
© Agilent Technologies, Inc. 2014
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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
EMC Back to Basics 2014
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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
EMC Back to Basics 2014
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EMC Back to Basics 2014
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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 Back to Basics 2014
7
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 Back to Basics 2014
8
EMC Market Segmentation
Emissions Radiated & Conducted - Compliance
- Pre-Compliance
Immunity Radiated & Conducted
Compliance
Measurement
Type:
Commercial Military Application:
- Product Type
- Product Class
- Country - .
Sub-segments:
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Definitions: Emissions, Susceptibility, Immunity
Radiated
Emissions
Conducted
Emissions
Conducted
Susceptibility
(or Immunity)
Radiated
Susceptibility
(or Immunity)
EMC Back to Basics 2014
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Measurement Equipment – Emissions
EUT EUT Mains
tran
sd
ucer
Radiated
Emissions
Compliance receivers
Spectrum Analyzers
Preamps
Antennas
Measurement SW
Towers
Turntables
Control SW
Open Sites
Anechoic Chambers
Semi-Anechoic Chambers
TEM cells
Reverberation chambers
Artificial Mains Networks
LISN - (line impedance stabilization network)
Conducted Transducers
Measurement SW
Equipment
Conducted
Emissions
EMC Back to Basics 2014
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Compliance vs. Precompliance Measurements
Precompliance Measurements
- “Unofficial” performance estimate done prior
to Full Compliance test
- Typically done with SA on available location
- Purpose is to minimize chance of failure at
Compliance test.
Full Compliance
- Pass/Fail final regulatory testing
- Requires specific equipment and test site - must comply to specific Mil or Comm’l standards
- Expensive and time consuming
MXE
X-Series w/
N6141A
EMC Back to Basics 2014
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Measurement Equipment – Immunity
EUT EUT AMN
tran
sd
ucer
Radiated
Immunity
Equipment
Conducted
Immunity
~
~
transducer
ES
D s
ourc
e
Screen rooms
TEM cells
GTEM cells
RF Sources
Power meters
Power amps
Antennas
Measurement SW
Control SW
LISN
Coupling Transducers
- clamps, etc.
ESD sources
EMC Back to Basics 2014
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Segmentation
Emissions Radiated & Conducted - Compliance
- Pre-Compliance
Immunity Radiated & Conducted
Compliance
Measurement
Type:
Commercial Military Application:
- Product Type
- Product Class
- Country - .
Sub-segments:
EMC Back to Basics 2014
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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
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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
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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
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IEC/CISPR Measurement Std. – CISPR 16
Equipment Std. – CISPR 16
Product Std. - CISPR 11-15, etc.
IEC 61XXX
GB
ANSI
FCC
CENELEC
EN
VCCI
Commercial Regulations
EMC Back to Basics 2014
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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
Canada CSA ICES xxx
Australia/NZ AS/NZS AS/NZS CISPR xx
Japan VCCI J550xx
China (Mainland)
CCC, MoD GB xxxx- xxxx
GJB xxx- xx (equivalent to Mil-STD)
Korea MIC Equivalent to EN 550xx
Taiwan BSMI CNS xxxx
EMC Back to Basics 2014
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Segmentation
Emissions Radiated & Conducted - Compliance
- Pre-Compliance
Immunity Radiated & Conducted
Compliance
Measurement
Type:
Commercial Military Application:
- Product Type
- Product Class
- Country - .
Sub-segments:
EMC Back to Basics 2014
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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
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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
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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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EMI Receiver Block Diagram
23
Input 1
Input 2
Attenuation
Transient
Limiter
RF Preselector
Analog IF
Filter
Pre-amp
ADC
Digital IF
Filter
Digital Log Amp
Digital Detectors
FFT
Swept vs . FFT
EMC Back to Basics 2014
MXE
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EMC Back to Basics 2014
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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
EMC Back to Basics 2014
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Broadband
signals
Narrow
band
signals
RF Preselector
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EMI Receiver Block Diagram
26
Input 1
Input 2
Attenuation
Transient
Limiter
RF Preselector
Analog IF
Filter
Pre-amp
ADC
Digital IF
Filter
Digital Log Amp
Digital Detectors
FFT
Swept vs . FFT
EMC Back to Basics 2014
MXE
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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
• Time Domain Scan (TDS)
• Very fast
• Highly overlapped FFT (>90%)
• Alternate scan method allowed by CISPR 16
EMC Back to Basics 2014
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FFT
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How Time Domain Sweep Saves Time
frequency
am
plit
ude
frequency
am
plit
ude
Receiver
FFT BW
Receiver
Resolution BW
Swept or Stepped
Frequency Scan Time Domain
Frequency Scan
28
Have to dwell at
each RBW
Only have to dwell for each
FFT BW (multiple RBWs)
EMC Back to Basics 2014
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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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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.
EMC Back to Basics 2014
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Key Specifications for EMI
• Sensitivity
• Amplitude Accuracy
• Scan Speed
• Others?
31
EMC Back to Basics 2014
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Signal
Equals
Noise
Sensitivity is the Smallest Signal That Can Be
Measured
2.2 dB
EMC Back to Basics 2014
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Specifications: Sensitivity/DANL
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10 dB
Attenuation = 10 dB Attenuation = 20 dB
signal level
Effective Level of Displayed Noise is a Function
of RF Input Attenuation
Signal To Noise Ratio Decreases as
RF Input Attenuation is Increased
EMC Back to Basics 2014
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Specifications: Sensitivity/DANL
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Decreased BW = Decreased Noise
100 kHz RBW
10 kHz RBW
1 kHz RBW
10 dB
10 dB
Displayed Noise is a Function of IF Filter
Bandwidth
EMC Back to Basics 2014
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Sensitivity/DANL: IF Filter (RBW)
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Sensitivity/DANL: Summary
Narrowest Resolution BW allowed
Minimum RF Input Attenuation
Sufficient Averaging (video or trace - if allowed)
Using the Preamp also improves sensitivity
Noise Floor Extension
For Best Sensitivity Use:
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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)
EMC Back to Basics 2014
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FFT
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Digital IF Improves Amplitude Accuracy
Input
Connector
Down-
conversion
IF
Gain
IF
Filter
Log
Amp Video
Filter
RF Input
Attenuator 2 dB Steps Pre-selector
Log ADC
ADC DSP
• Input connector (mismatch)
• Calibrator
• RF input attenuator
− flatness and switching
• Mixer and input filter
− frequency response
Digital IF improves Amplitude Accuracy:
• Ref Level switching uncertainty (IF gain)
− Level correction digitally synthesized
• RBW filter switching uncertainty
− RBWs all digitally synthesized
• Display scale fidelity (Log Amp)
− Log response & display scaling digitally
synthesized
Frequency
Dependent Frequency
Independent
EMC Back to Basics 2014
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Digital IF Improves Amplitude Accuracy
Input
Connector
Down-
conversion
IF
Gain
IF
Filter
Log
Amp Video
Filter
RF Input
Attenuator 2 dB Steps Pre-selector
Log ADC
ADC DSP
Digital IF improves Amplitude Accuracy:
• Ref Level switching uncertainty (IF gain)
− Level correction digitally synthesized
• RBW filter switching uncertainty
− RBWs all digitally synthesized
• Display scale fidelity (Log Amp)
− Log response & display scaling digitally
synthesized
Frequency
Dependent Frequency
Independent
Amplitude
Uncertainty
N9038A
Receiver Analog IF
(older receivers)
Ref Level
Switching 0dB <= +/- 1dB
RBW
Switching +/- .05dB <= +/- .5dB
Display Scale
Fidelity +/- .15dB <= +/- .85dB
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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
Pre-scan
Data Reduction
Maximization
Final Measurement
Report Generation
• Recommended by CISPR
• Measurement methodology
found in CISPR 16-2-3
• Fastest way to make the
measurement
• MIL Measurements*
EMC Back to Basics 2014
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• Preview spectrum
using “Peak” detector
• Measurement Parameters
– Frequency range
– Limit lines
– Margins
– Antenna Factors
– Scan Type
• Scan Types
– Stepped
– Swept
– Time Domain
Pre-Scan
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Pre-scan Data Reduction Maximization Final
Measurement Report
Generation
Prescan
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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
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Pre-scan Data Reduction Maximization Final
Measurement Report
Generation
Signal List
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Maximization Techniques Maximize signal amplitude before final measurement
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Pre-scan Data Reduction Maximization Final
Measurement Report
Generation
• Monitor Spectrum
– Simultaneous spectrum and meter measurements
– Access to signal (suspect) list
– Meter max hold
• Spectrum Analyzer mode
– Switch between EMI receiver and SA
modes using global center frequency
– Powerful analyzer mode
Receiver mode
Spectrum Analyzer Mode
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Final Measurement
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Pre-scan Data Reduction Maximization Final
Measurement Report
Generation
• Signals in list are
automatically
measured
• Measure suspect signals
with Quasi-peak, EMI
average detector, etc.
• Suspect signals still
failing? Start
troubleshooting?
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Report Generation
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Pre-scan Data Reduction Maximization Final
Measurement Report
Generation
• Report Generator
– Settings
– Screenshots
– Tables Report Format: PDF or HTML
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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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Transducers for EMI measurements
• Near Field Probe
• Near Field Scanner
• Line Impedance Stabilization Network (LISN)
• Antennas
• Other devices?
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“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
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Near Field Probes – E & H Field
• Use Cases
– Pre-compliance
– Diagnostics
• Characteristics
– Frequency Range
– Spatial Resolution
– Sensitivity
• Measure or Generate Fields
– Emissions or Susceptibility
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E Field Probe
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
Power Mains
EUT
No Transient
Limiter Required
LISN
MXE Receiver
Types of LISNs
• V-LISN
• Delta LISN
• T-LISN
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EMI Broadband Antenna Examples
Double ridged horn
Hybrid Log Periodic
Biconical
Log Periodic Hybrid Log Periodic
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“Ratio of the electric field to the
voltage out of the antenna”
AF = 𝐸𝑖𝑛
𝑉𝑜𝑢𝑡
Understanding Antenna Factors
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AF = Antenna Factor (1/m)
E = Electric Field units (V/m)
V = Voltage output from antenna (V)
Log Units
Linear Units
AF(dB/m) = E(dBµV/m) –V(dBµV)
Typical biconical antenna factors
Ante
nna F
acto
r (d
B/m
)
Frequency (MHz) 20 150 300
20
10
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Antenna Factors on a Typical Display
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Corrected
for a
broadband
antenna
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Examples of Test Facilities
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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.
*Anechoic material is made
of carbon impregnated
rubberized cones or ferrite
tiles or both
Origin
Anechoic
an- “not” + echoic (echo)
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Examples of Test Facilities
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Open Area Test Site (OATS)
• Useful in low ambient signal
environments
GHz Transverse Electro Magnetic Cell
(GTEM Cell)
• Used for smaller devices. Can be
used for immunity and emissions.
Reverberation Chamber
• Uses a mode stirring tuner to
generate a uniform field (no
absorption material on the walls)
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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
Chamber Control
Room • Automation software typically
communicates with the receiver
over LAN or GPIB
• Uses SCPI commands
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Questions? Please type them in the chat box now
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N9038A MXE EMI Receiver X-Series Signal/Spectrum Analyzers
www.agilent.com/find/mxe
www.agilent.com/find/x-series