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EMC seminar Page 1 Misure di compatibilita’ Elettromagnetica Roberto Sacchi Electronic Measurements Group Agilent Technologies
EMC seminar
Page 1
Misure di compatibilita’
Elettromagnetica
Roberto Sacchi
Electronic Measurements GroupAgilent Technologies
EMC seminar
Agenda Introduzione alle misure EMI
Terminologia;
Sistema di misura (antenna, LISN, ricevitore, etc.);
Detectors;
Normative europee ed internazionali
Misure di compatibilita’ elettromagnetica Misure di emissioni radiate
Misure di emissioni condotte
Misure di immunita’ (EMS)
Setup di misura
Camere anecoiche vs. OATS (Open Area Test Site)
Soluzioni Agilent Introduzione al nuovo ricevitore EMI Full Compliance Agilent MXE
Uso degli analizzatori Agilent della Serie-X per misure EMI pre-compliance.
Sorgenti per i test di immunita’
Software applicativo
Soluzioni complete tramite i nostri partners
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Pre-compliance vs. Full compliance measurements
Page 3
Pre-compliance measurementsEvaluate the conducted and radiated
emissions of a device using correct
detectors and bandwidths before going
to a test house for compliance testing
Full Compliance measurementsFull compliance testing requires a receiver
that meets all the requirements of CISPR
16-1-1 (response to a CISPR pulse gen), a
qualified open area test site or semi
anechoic chamber and an antenna tower
and turntable to maximize EUT signals.
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What is EMC?
Electromagnetic Compatibility (EMC): The ability of equipment to function
satisfactorily in its electromagnetic environment without introducing intolerable
disturbances into that environment or into other equipment.
Combination of Interference and Immunity.
Electromagnetic Interference (EMI):Electromagnetic energy emanating from one device which causes another device to
have degraded performance.
Electromagnetic Immunity (Susceptibility, EMS): Tolerance in the presence
of electromagnetic energy (Performance degradation due to electromagnetic energy).
Compliance measurements require a receiver that meets the requirements of
CISPR part 16 (for commercial) or MIL-STD-461 (for military).
All EMI receivers require a pre-selector at lower frequencies to limit the input energy
and maintain sufficient dynamic range to meet the CISPR 16 requirements.
EMC seminar
Definitions
EMC –
ElectroMagnetic Compatibility
EMI –
ElectroMagnetic
Interference
EMS –
ElectroMagnetic
Susceptibility
(aka Immunity)
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EMI measurement system
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Compliance EMI receiver requirements
A CISPR 16-1-1 receiver must have the following functionality in
the range 9 kHz - 18 GHz:
A normal +/- 2 dB absolute accuracy
CISPR-specified resolution bandwidths (-6 dB)
Peak, quasi-peak, EMI average, and RMS average detectors
Specified input impedance with a nominal value of 50 ohms; deviations
specified as VSWR
Be able to pass product immunity in a 3 V/m field
Be able to pass the CISPR pulse test (implies pre-selector below 1 GHz)
Other specific harmonic and intermodulation requirements
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Receiver requirements above 1 GHz
Above 1 GHz regulations require:
1 MHz bandwidth for measurements
No quasi-peak detector
No CISPR pulse test, meaning no additional pre-selector required
excellent sensitivity
According to current FCC regulations, the maximum test frequency is the
fifth harmonic of the highest clock frequency for an “unintentional radiator”
(for example, computers without wireless connectivity) and the tenth
harmonic for an intentional radiator (such as a cellular phone or wireless
LAN).
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What is an EMI Receiver?Let’s begin with a spectrum analyzer
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•Display and measure amplitude versus frequency for RF & MW signals
•Separate or demodulate complex signals into their base components (sine waves)
Spectrum Analysis
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OverviewTypes of Tests Made
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Modulation
Noise
Distortion
EMC
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Architecture of Modern Spectrum/Signal Analyzers
What does “Modern” mean?
Digitize the IF output, not detector output
FFT and swept capability (neither one is optimum for everything)
Data output available
Connectivity
Automated measurement features
Ability to use new features and duplicate or expand necessary old ones
Complete spectrum analyzer & vector signal analyzer
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Theory of OperationSwept Spectrum Analyzer Block Diagram
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Pre-Selector
Or Low Pass
Input Filter
Crystal
Reference
Oscillator
Log
Amp
RF input
attenuator
mixer
IF filter
(RBW)envelope
detector
video
filterlocal
oscillator
sweep
generator
IF gain
Input
signal
ADC, Display
& Video
Processing
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Traditional Spectrum Analyzer
Scalar analysis
Digitizing the video signal
Classic superheterodyne swept spectrum analyzer
Product detector
loss of phase
information
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Digital IF Spectrum/Signal Analyzer
Vector data CAN be preserved (mag/phase or I/Q)
Digitizing the IF Signal
Some troublesome operations
and conversions are now
fast, accurate DSP
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OverviewDifferent Types of Analyzers
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Parallel filters measured
simultaneouslyA
ff1 f2
FFT Analyzer
A
ff1 f2
Filter 'sweeps' over
range of interest
Swept Analyzer
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SpecificationsResolution: RBW Type Determines Sweep Time
280 sec
134 sec
13.5 sec
8563E Analog RBW
PSA Digital RBW
PSA FFT RBW
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Speed Improvements
Useful comparisons highly specific, many factors
PXA mode switching typically faster than PSA
Where speed is critical, consider modifying measurement routines to
include features such as list sweep
Benchmark PXA PSASpeed
improvement
Preset (*RST) 28 ms 168 ms 6x
Marker peak search 6.5 ms 78 ms 12x
Local Update 13 ms 17 ms 1.3x
CF Tune and Transfer (4 - 5GHz) 109 ms 186 ms 1.7x
Remote sweep and trace transfer 18 ms 30 ms 1.67x
Nominal speed comparison, PSA example:
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Modern spectrum analyzer
Resolution BW Selectivity or Shape Factor
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3 dB
60 dB
60 dBBW
60 dB BW
3 dB BW
3 dB BW
Selectivity =
Determines resolvability of unequal amplitude signals
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Specifications
Resolution: RBW Type and Selectivity
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DIGITAL FILTER
ANALOG FILTER
SPAN 3 kHzRES BW 100 Hz
Typical
Selectivity
Analog 15:1
Digital ≤5:1
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Digital Filter Shape
Better shape factor, biggest selectivity benefit for different signal levels
Equivalent selectivity at a wider, faster-sweeping RBW
digital filters swept an additional 3-4x faster
30 kHz Digital Filter
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CISPR Bandwidth Requirements
Measurement Range CISPR Band CISPR Bandwidth
9 KHz – 150KHz A 200 Hz
150 KHz – 30 MHz B 9 KHz
30 MHz – 1 GHz C/D 120 KHz
> 1GHz E 1 MHz
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Bandwidth -6dB
-20dB
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MIL-STD-461 Bandwidth Requirements
Measurement Range -6dB Bandwidth
30Hz - 1 KHz 10 Hz
1 KHz -10 KHz 100 Hz
10 KHz - 150 KHz 1 KHz
150 KHz - 30MHz 10 KHz
30 MHz - GHz 100 KHz
> 1GHz 1 MHz
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Some modern analyzers approach accuracy of power meter + sensor
• Even better for low-level signals, with narrower noise bandwidth and
the benefit of frequency selectivity
Some factors determining uncertainty:
• Input connector (mismatch)
• RF input attenuator
• Mixer and input filter (flatness)
• IF gain/attenuation (reference level)
• RBW filters
• Display scale fidelity
• Calibrator
Modern Spectrum Analyzer Accuracy
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Modern Spectrum Analyzer Accuracy Examples
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Line Impedance Stabilization Networks (LISN)
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Purpose of a LISN:
1. Isolates the power mains from the
equipment under test. The power
supplied to the EUT must be as clean as
possible. Any noise on the line will be
coupled to the X-Series signal analyzer
and interpreted as noise generated by
the EUT.
2. Isolates any noise generated by the EUT
from being coupled to the power mains.
Excess noise on the power mains can
cause interference with the proper
operation of other devices on the line.
3. The signals generated by the EUT are
coupled to the X-Series analyzer using a
high-pass filter, which is part of the LISN.
Signals that are in the pass band of the
high-pass filter see a 50-Ω load.
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LISN
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LISN
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@ Electrical Network Frequency
@ 150 kHz to 30 MHz
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Transient Limiter
The purpose of the limiter is to protect the input of the EMC analyzer from
large transients when connected to a LISN. Switching EUT power on or off
can cause large spikes generated in the LISN.
The Agilent 11947A transient limiter incorporates a limiter, high-pass filter,
and an attenuator. It can withstand 10 kW for 10 μsec and has a frequency
range of 9 kHz to 200 MHz. The high-pass filter reduces the line frequencies
coupled to the EMC analyzer.
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DUT
LimiterLISN
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Field Strength Unit
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Radiated EMI emissions measurements measure the
electric field. The field strength is calibrated in dBμV/m.
Pt = total power radiated from an isotropic radiator
Pd = the power density at a distance from the isotropic radiator
(far field >λ/2π)
24 r
PP t
d
120R
R
EPd
2
2
2
4 r
P
R
E t
r
PE
t 30 [V/m]
[ohm]
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Field Strength and Antenna factors
Radiated EMI emissions tests measure the electric field. The
field strength is calibrated in dBμV/m.
Antenna factors is the ratio of the electric field (V/m) present
at the plane of the antenna versus the voltage out of the
antenna connector.
Log units:
AF(dB/m) = E(dBμV/m) - V(dBμV)
E(dBμV/m) = V(dBμV) + AF(dB/m)
Notes:
Antenna factors are not the same as antenna gain.
dBμV = dBm + 107
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Antennas used in EMI emission measurements
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Detectors: Convert IF Samples to Display Bins or
“Buckets”
Multiple simultaneous detectors
Screen Shot “Detector 3types”
Time
Volts
Peak
Neg Peak
Sample
Display points or
buckets
Normal, Average, Neg Peak
Peak, Neg Peak, Sample
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Detectors
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Most radiated and conducted limits are based on quasi-peak
detection mode.
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Peak vs. Quasi-peak vs. Average
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time
VPeak Detection
Quasi-Peak Detection
Average Detection
time
VPeak Detection
Quasi-Peak DetectionAverage Detection
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Peak ≧ QP ≧AveragePeak Detector
• Initially used
• Faster than QP and Average modes
• If all signals fall below the limit, then the product passes and no future
testing is needed.
QP
• For CW signal, Peak = QP
• Much slower by 2 or 3 order magnitude compared to using Peak detector
• Charge rate much faster than discharge rate
– the higher repetition rate of the signal, the higher QP reading
Average
• Radiated emissions measurements above 1 GHz are performed using
average detection
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Close field probe
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Measures the magnetic field H strength at the center
of its sense loop. The plane of the probe tip loops
must be perpendicular to the radiating magnetic field
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Test example
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International emissions regulations (summary)
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CISPR changes…
RMS-Average
Preselector-less testing: enables use of spectrum analyzer for specific
test cases.(no emissions with PRF < 20 Hz)
CISPR 22 to 6 GHz
Time Domain: sometimes required for the automotive market
APD: soon to be required by CISPR11
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European Norms example
EN55014 (CISPR 14)
This standard applies to electric motor-operated and thermal
appliances for household and similar purposes, electric tools
and electric apparatus.
Limit line use depends upon the power rating of the item.
EN55014 distinguishes between household appliances, motors
less than 700W, less than 1000W and greater than 1000W.
Limits for conducted emissions are 150 kHz to 30 MHz, and
limits for radiated emissions are 30 MHz to 300 MHz.
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The compliance measurement process
Before making measurements on your product, some
preliminary questions must be answered.
1. Where will the product be sold (for example, Europe, United
States, Japan)?
2. What is the classification of the product?a. Information technology equipment (ITE)
b. Industrial, scientific or medical equipment (ISM)
c. Automotive or communication
d. Generic (equipment not found in other standards)
3. Where will the product be used (for example home,
commercial, light industry or heavy industry)?
With the answers to these questions, you can determine
which standard your product must be tested against.
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General Process for Making EMI Measurements
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Determine the country or countries in which the product
will be sold which in turn identifies the regulator agency.
Select the limit lines to be tested to (conducted/radiated).
Select the band to be used.
Correct for transducer loses and amplifiers gains.
Identify signals above the limit that must be evaluated.
Zoom in on failed signal and perform quasi-peak or
average measurements.
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Conducted Emissions Measurements
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1. Connect DUT to the test system
2. Set the proper frequency range
3. Load limit lines and correction factors for LISN and limiter
4. View the ambient emissions with DUT OFF
5. Switch on the DUT and find signals above limits by using peak detector
6. Measure all signals above limits with quasi-peak and average detectors
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Radiated Emissions are difficult to
measure because of multiple
dimensions (five) and the use of
quasi-peak detection below 1GHz
41.2563MHz
218.120MHz
1500.260MHz
1 - Azimuth
2 - Antenna Height
3 - Field Strength
4 - Frequency
5 -Time
The challenge of measuring radiated emissions
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Radiated Emissions Measurements
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1. Connect the antenna
to the EMI receiver and
separate the antenna from
the DUT as specified by the
regulation requirements
2. Set the proper frequency
range and bandwidth
3. Load limit lines and
correction factors for
antenna and cable.
4. With DUT OFF, measure the ambient emissions and store them
5. Switch on the DUT and find signals above limits by using peak detector (only those
not present during the ambient scan). Rotate the DUT to maximize the emissions.
6. Measure all signals above limits with quasi-peak and average detectors
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Open Area Test Site (OATS)
EUTs are measured in an open area test site (OATS) or anechoic chamber.
ANSI C63.4 and CISPR 16-1-1 specify the requirements for an OATS, including:
Preferred measurement distances
of 3, 10, and 30 meters
Antenna positioning at 1 to 4 meter
Heights
An area called the “CISPR ellipse”
of major diameter 2X and minor
diameter √3 • X, where X is the
measurement distance; the ellipse
must be free of any reflecting objects
A metal ground plane for the measurement area
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Note: 10 meter anechoic chambers and GTEM cells can also be used for radiated
compliance measurements.
EMC seminar
1. Select the measurement range
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2. Load Corrections factors
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Amplitude at
point circled
Amplitude
referenced to
blue line
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3. Load Limit line
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Circle indicates
the position of
the amplitude
frequency pair
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4. Scan for signals above the limits with peak detector
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5. Quasi-peak and average measurements
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Troubleshooting
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Use the close-field probe to locate the sources of the radiated signals
exceeding the limit lines
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Immunity test setup
Conducted Immunity
100 kHz – 1 GHz
Amplifiers
HF-Switch
Radiated Immunity
30 MHz – 18 GHz
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Agilent Solutions
Page 55
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What is a CISPR 16-1-1 Compliant Receiver
CISPR 16-1-1 is the document that defines the
functionality of an EMI receiver
Detectors
N9038A MXE EMI receiver is CISPR 16-1-1 2010 Compliant
Frequency
response
CISPR is a subcommittee of the IEC
EMC seminar
X-Series
signal
analyzer
CISPR 16
compliant
EMI receiver
What is the MXE EMI Receiver?
The Agilent MXE is more than a CISPR 16-1-1 compliant EMI
receiver
It is also an X-Series signal analyzer that can run a variety of
measurement applications
The MXE can evolve as technology changes
20 Hz to 1 GHz for
Conducted Emissions
(built-in limiter)
20 Hz to 26.5
GHz for
Radiated
Emissions
Compliant
Preselection 20 Hz
to 3.6 GHz in both
EMI Receiver
Mode and SA
Mode on
Both Inputs
CISPR 16-1-1 2010
Compliant EMI Receiver
N9038A MXE EMI Receiver
in 30 seconds
Run X-Series
applications
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LB
CFB
RFB
INB
DDS
Noise Source
20 Hz -1GHz
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Agilent X-Series Signal Analyzers
Multiple instruments in one box: Swept spectrum analyzer;
FFT analyzer;
RF and Baseband Vector Signal analyzer;
Noise Figure analyzer.
Fastest signal analysis measurements
Broadest set of applications and demodulation capabilities
Upgradeable HW
Most advanced user interface & world-class connectivity
Instrument ArchitectureModern Spectrum Analyzers Architecture (PSA, X-Series)
RF Section IF Section BB Section
•Attenuation
•Filtering
•Downconversion• RBW Filtering
• Envelope Detection
• Log Conversion
• VBW Filtering
• Peak/sample/rms
detection
• Averaging
ADCIF/BB Section
on ASIC
“All Digital” IF Architecture
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Modern Spectrum Analyzer Block Diagram
YIG ADC
Analog IF
FilterDigital IF Filter
Digital Log Amp
Digital Detectors
FFT
Swept vs. FFTAttenuation
Pre-amp
Replaced
by
“All Digital IF” Advantages
RF Section ADCIF/BB Section
on ASIC
Flexibility:
RBW filtering in 10% steps
Filters with better selectivity
Multiple operation modes (Swept, FFT, VSA, NFA)
Accuracy:
Log conversion practically ideal
No drift errors; increased repeatability
Speed:
When Swept mode is slow, go FFT
FFT
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Techniques for Reducing DANL, Improving Dynamic
Range
Reduce attenuation
Add preamp
Reduce RBW
Add external filtering
Better/shorter cables, connectors
Move analyzer closer
Time averaging (where possible, not measurement avg.)
Measurement processing (take advantage of Moore’s Law)
• Noise power subtraction/noise correction/NNC
• Noise floor extension (NFE) leverages deep knowledge of
analyzer/circuit behavior
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CW Signal Measured Near Analyzer Noise Floor
Actual S/N
Displayed
S/N
CW Signal
Apparent
Signal
This is
fundamental, and
often missedAmpl & Freq
Axes Expanded
Example: No noise subtraction or near noise correction
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Noise Floor Subtraction
Analyzer noise adds incoherently to any signal to be measured
Power calculations are performed on a linear power scale
(watts, not dBm) and results typically are shown in dBm
PobsS+N = PobsN + PS
PS = PobsS+N − PobsN
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Noise Subtraction, “Noise Floor Extension”
New technique “NFE” improves D.A.N.L.
analyzer noise power calculated/subtracted real time
3 dB error
without NFE
“No” error
Improved noise floor
or displayed average
noise level
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Analyzer Noise Floor with NFE
Source still off, green trace shows analyzer noise level with NFE
Other measurement conditions unchanged
Note high variance result from subtraction of small, noisy numbers
Analyzer DANL now far enough below source for minimal(0.2 - 0.4 dB) error
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A Closer Look
Pink trace adds to blue trace; result is yellow trace (NFE not used)
Green trace is included in blue trace but resulting error very small
Source noise Level, no NFE
Source Noise Level, with NFE
Analyzer Noise, no NFE
Analyzer Noise with NFE
EMI Roadmap
6/28/2011Page 70
EMC Features standard in all X-Series Spectrum
analyzers
• Limit Lines (2000 pts)
• Amplitude correction (2000 pts)
• 40001 sweep points
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Option EMC in X-Series spectrum analyzer
CISPR 16-1-1 detectors
(to latest spec)
Quasi Peak
EMI Average (“CISPR-AVG”)
RMS Average (“CISPR-RMS”)
EMI Bandwidths (CISPR & MIL STD)
EMI Presets
Tune & Listen
Measure at Marker
EMI Peak, EMI Average, and
Quasi Peak measurements
displayed together
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Full Featured Pre-compliance Application
Available in all X-Series models
W/N6141A EMC measurement application
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Log Display
Peak List
Auto-detect peaks
Limit Delta
Realtime
Meters
with any 3
Simultaneous
Detectors
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N6141A measurement: Frequency Scan with Log Display
- same functionality as E7400 Signal List
Meters tune
to selected
signal
EMI Roadmap
6/28/2011Page 77
N6141A measurement: Strip Chart
• Time record
of zero span
data scrolls
to left
• Up to three
different
detectors
• Can be used
to make
“click”
measure-
ments
Click measurements are made on home appliances
Patent
Applied
For
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Option EDP (Enhanced Display Package) for the SA
• Spectrogram
• Trace Zoom
• Zone Span
Group/Presentation Title
Agilent Restricted
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Pre-compliance
Compliance
N6141A EMI Measurement Application
PXA
MXA
CXAAgilent MXE N9038A
EXA
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Agilent products for Immunity test (EMS)
Signal
generator9 kHz – 3 GHz, AM, FM, Phase, Pulse IQ Modulator,
40 MHz Mod.-BW
Signal
generator
N5182, N5182, N5183
100 kHz- 1,3, 6, 20, 40 GHz, AM, FM, Phase, Pulse,
optional vector, 120 MHz Mod.-BW, step , sweep,
USB-Power meter included
Power meter/
Power sensors
E441x, E191x, N8262, U200x
100 kHz – 40 GHz
single channel, dual channel, USB, peak, envelope,
pulse
Accessories Directional Couplers, cables, Adapters, Switches etc.
EMC seminar
Solution partners for EMC
Complete solution:
1. Automation software
2. Chambers
3. GTEM
4. Antennas
5. Power amplifiers
6. Accessories
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Per documentazione su prodotti ed applicazioni EMI/EMC visitare il sito
http://www.agilent.com/find/EMC
Contatti:
Agilent Technologies ItaliaRoberto SacchiApplication EngineerE-mail: [email protected]
Giuseppe SavoiaSignal Analysis and Generation Sales SpecialistE-mail: [email protected]
Agilent Contact CenterE-mail: [email protected]: 02 9260 8484
