Misure di compatibilita’
Elettromagnetica
Roberto Sacchi
Electronic Measurements Group
Agilent Technologies
EMC seminar
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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
EMC seminar
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Pre-compliance vs. Full compliance measurements
Pre-compliance measurements
Evaluate the conducted and radiated
emissions of a device using correct
detectors and bandwidths before going
to a test house for compliance testing
Full Compliance measurements
Full 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
Spectrum Analysis
•Display and measure amplitude versus frequency for RF & MW signals
•Separate or demodulate complex signals into their base components (sine waves)
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Overview
Types of Tests Made
Modulation
EMC
Noise
Distortion
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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)
Complete spectrum analyzer & vector signal analyzer



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Data output available
Connectivity
Automated measurement features
Ability to use new features and duplicate or expand necessary old ones
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Theory of Operation
Swept Spectrum Analyzer Block Diagram
RF input
attenuator
mixer
IF gain
IF filter
(RBW)
Input
signal
envelope
detector
Log
Amp
Pre-Selector
Or Low Pass
Input Filter
local
oscillator
video
filter
sweep
generator
Crystal
Reference
Oscillator
ADC, Display
& Video
Processing
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Traditional Spectrum Analyzer
Scalar analysis
Digitizing the video signal
Product detector
loss of phase
information
Classic superheterodyne swept spectrum analyzer
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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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Overview
Different Types of Analyzers
FFT Analyzer
A
Swept Analyzer
Parallel filters measured
simultaneously
f1
f2
A
f
Filter 'sweeps' over
range of interest
f1
f2
f
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Specifications
Resolution: RBW Type Determines Sweep Time
8563E Analog RBW
PSA Digital RBW
PSA FFT RBW
280 sec
134 sec
13.5 sec
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Speed Improvements
Nominal speed comparison, PSA example:
Benchmark
PXA
PSA
Speed
improvement
Preset (*RST)
Marker peak search
Local Update
CF Tune and Transfer (4 - 5GHz)
Remote sweep and trace transfer
28 ms
6.5 ms
13 ms
109 ms
18 ms
168 ms
78 ms
17 ms
186 ms
30 ms
6x
12x
1.3x
1.7x
1.67x
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
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Modern spectrum analyzer
Resolution BW Selectivity or Shape Factor
3 dB
3 dB BW
60 dB
60 dB
BW
Selectivity
=
60 dB BW
3 dB BW
Determines resolvability of unequal amplitude signals
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Specifications
Resolution: RBW Type and Selectivity
ANALOG FILTER
Typical
Selectivity
Analog 15:1
Digital ≤5:1
DIGITAL FILTER
RES BW 100 Hz
SPAN 3 kHz
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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
Bandwidth
-6dB
-20dB
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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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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Modern Spectrum Analyzer Accuracy
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
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Modern Spectrum Analyzer Accuracy Examples
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Line Impedance Stabilization Networks (LISN)
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
@ 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.
Limiter
LISN
DUT
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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Field Strength Unit
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)
Pt
Pd 
4   r 2
R 120  
E2
Pd 
R
Pt
E2

R 4   r 2
[ohm]
E
Pt  30
r
[V/m]
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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
Peak, Neg Peak, Sample
Normal, Average, Neg Peak
Display points or
buckets
Peak
Volts
Sample
Neg Peak
Screen Shot “Detector 3types”
Time
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Detectors
Most radiated and conducted limits are based on quasi-peak
detection mode.
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Peak vs. Quasi-peak vs. Average
V
Peak Detection
Quasi-Peak Detection
Average Detection
time
V
Peak Detection
time
Quasi-Peak Detection
Average Detection
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Peak ≧ QP ≧Average
Peak 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
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
EMC seminar
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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.
b.
c.
d.
Information technology equipment (ITE)
Industrial, scientific or medical equipment (ISM)
Automotive or communication
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

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
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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The challenge of measuring radiated emissions
Radiated Emissions are difficult to
measure because of multiple
dimensions (five) and the use of
quasi-peak detection below 1GHz
5 -Time
1 - Azimuth
2 - Antenna Height
3 - Field Strength
1500.260MHz
218.120MHz
4 - Frequency
41.2563MHz
Radiated Emissions Measurements
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
Note: 10 meter anechoic chambers and GTEM cells can also be used for radiated
compliance measurements.
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1. Select the measurement range
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2. Load Corrections factors
Amplitude at
point circled
Amplitude
referenced to
blue line
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3. Load Limit line
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
Use the close-field probe to locate the sources of the radiated signals
exceeding the limit lines
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Immunity test setup
Radiated Immunity
30 MHz – 18 GHz
Amplifiers
HF-Switch
Conducted Immunity
100 kHz – 1 GHz
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Agilent Solutions
EMC seminar
Page 55
What is a CISPR 16-1-1 Compliant Receiver
CISPR is a subcommittee of the IEC
CISPR 16-1-1 is the document that defines the
functionality of an EMI receiver
Detectors
Frequency
response
N9038A MXE EMI receiver is CISPR 16-1-1 2010 Compliant
EMC seminar
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
X-Series
signal
analyzer
CISPR 16
compliant
EMI receiver
EMC seminar
N9038A MXE EMI Receiver
in 30 seconds
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
20 Hz to 1 GHz for
Conducted Emissions
(built-in limiter)
Run X-Series
applications
20 Hz to 26.5
GHz for
Radiated
Emissions
LB
20 Hz -1GHz
CFB
INB
DDS
RFB
Noise Source
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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
EMC seminar
Instrument Architecture
Modern Spectrum Analyzers Architecture (PSA, X-Series)
RF Section
•Attenuation
•Filtering
•Downconversion
ADC
IF Section
BB Section
IF/BB Section
on ASIC
• RBW Filtering
• Envelope Detection
• Log Conversion
• VBW Filtering
• Peak/sample/rms
detection
• Averaging
“All Digital” IF Architecture
Modern Spectrum Analyzer Block Diagram
Analog IF
Filter
Pre-amp
Digital IF Filter Digital Detectors
FFT
Attenuation
Swept vs. FFT
YIG
Digital Log Amp
AD
C
Replaced
by
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“All Digital IF” Advantages
RF Section
ADC
FFT
IF/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
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
Example: No noise subtraction or near noise correction
Apparent
Signal
Displayed
S/N
Actual S/N
CW Signal
Ampl & Freq
Axes Expanded
This is
fundamental, and
often missed
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Noise Floor Subtraction
PobsS+N = PobsN + PS
PS = PobsS+N − PobsN
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
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Noise Subtraction, “Noise Floor Extension”
New technique “NFE” improves D.A.N.L.
analyzer noise power calculated/subtracted real time
“No” error
3 dB error
without NFE
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
Source noise Level, no NFE
Source Noise Level, with NFE
Analyzer Noise, no NFE
Analyzer Noise with NFE
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
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EMC Features standard in all X-Series Spectrum
analyzers
• Limit Lines (2000 pts)
• Amplitude correction (2000 pts)
• 40001 sweep points
EMI Roadmap
Page 70
6/28/2011
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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W/N6141A EMC measurement application
 Full Featured Pre-compliance Application
 Available in all X-Series models
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Log Display
Auto-detect peaks
Peak List
Page 75
Realtime
Meters
with any 3
Simultaneous
Detectors
Limit Delta
N6141A measurement: Frequency Scan with Log Display
- same functionality as E7400 Signal List
Meters tune
to selected
signal
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N6141A measurement: Strip Chart
• Time record
of zero span
data scrolls
to left
• Up to three
different
detectors
• Can be used
to make
“click”
measurements
Patent
Applied
For
Click measurements are made on home appliances
EMI Roadmap
Page 77
6/28/2011
Option EDP (Enhanced Display Package) for the SA
• Spectrogram
• Trace Zoom
• Zone Span
Group/Presentation
Title
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Agilent Restricted
Page 78
N6141A EMI Measurement Application
PXA
MXA
Pre-compliance
EXA
CXA
Compliance
Agilent MXE N9038A
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Agilent products for Immunity test (EMS)
Signal
generator
9 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.
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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 Italia
Roberto Sacchi
Application Engineer
E-mail: roberto_sacchi@agilent.com
Giuseppe Savoia
Signal Analysis and Generation Sales Specialist
E-mail: giuseppe_savoia@agilent.com
Agilent Contact Center
E-mail: contactcenter_italy@agilent.com
Tel:
02 9260 8484
EMC seminar