EMI Debug using a
Rohde&Schwarz Oscilloscope
Ing. Leonardo Nanetti
Businnes Development manager
EMI Measurements in different design phases
How R&S Products contribute to EMI Measurements
Design
Prototype
R&D
•
•
•
Manufacturing
Pre-Production
•
•
•
Design verifications
Specifications Testing
Product reviews
‫ ו‬Top performance
‫ ו‬High accuracy
‫ ו‬Beyond specs
verifications
New
ESR3/7
Manufacturing
Pre-Compliance
QA Testing implementation
Compliance Test
‫ ו‬CISPR16
compliance
‫ ו‬High speed time
domain scan
‫ ו‬Real- time spectrum
‫ ו‬Fast captures of
spurious noise
‫ ו‬Correlate time &
frequency domain
‫ ו‬Fast & accurate
measurements
‫ ו‬Entry level
‫ ו‬Combo of EMI test
receiver & spectrum
‫ ו‬Fully automated
‫ ו‬Pre-certification
EMI Test
‫ ו‬Fast & reliable
‫ ו‬Hi performance
‫ ו‬Wide variety of
measurements
‫ ו‬Good level of
accuracy
‫ ו‬Reliable
‫ ו‬Many meas. functions
‫ ו‬Entry level
EMI-EMC KIT
Fastest EMI test receiver
- Time domain scan
- Real time spectrum
- Frequency Mask Trigger
- Spectrogram
- Persistence Mode
‫ ו‬Good level of accuracy
‫ ו‬Reliable
‫ ו‬Many meas. functions
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EMC Applications for Oscilloscopes
EMI
EMS
Radiated
Interference
Conducted
Interference
Power Quality
EN55011, EN55012,
EN55013, EN55014,
EN55015, EN55022,
CISPR
EN55011, EN55012,
EN55013, EN55014,
EN55015, EN55022,
CISPR
EN61000-3-2
EN60555-2
EN61000-3-3
EN60555-3
ESD, EFT and
Burst Calibration
EN61000-4-2
EN61000-4-4
EN61000-4-5
EUT Monitoring
EN61000-4-3
Power Harmonics
Flicker
Measurement
RTO: An powerful tool for EMI/EMS debugging and precompl. applications
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R&S RTO Digital Oscilloscope
ı R&S RTO Product Details
# 1. High Signal Fidelity
# 2. Leading Acquisition Rate
# 3. Unique Digital Trigger
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Created to be unique – RTO oscilloscopes
ı Fastest detection of
rare signal faults
ı High accuracy and
Fastest
signal acquisition
& analysis
signal fidelity
l Optimized usage of
touch screen display
l Intuitive user interface
l Minimized trigger jitter
l New functionalities
New
benchmark
in usability
Most
innovative
trigger system
R&S RTO Instrument Structure
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R&S RTO Digital Oscilloscope
ı R&S RTO Product Details
# 1. High Signal Fidelity
# 2. Leading Acquisition Rate
# 3. Unique Digital Trigger
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#1 High Signal Fidelity: Convincing Accuracy
Low Noise Front End
ı Noise floor directly affects the sensitivity of the oscilloscope
ı Noise floor is determined by the noise characteristics of the components in the
signal path of the front end
 Variable Gain Amplifier (VGA)
 ADC
 Front end Layout and shielding
ADCs
* Specified. Typical lower
Front end
& Amplifiers
Benefit of lower noise:
Channel-to-Channel Isolation
> 60dB!
- Better Test Margin
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Input channels
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#1 High Signal Fidelity: Convincing Accuracy
Single Core ADC
ı ADC-Picture
RTO Single Core ADC
Single-core monolithic 10GS/s ADC vs Multiple ADCs in Single chip
> 7 ENOBs !
High Accuracy without using interleaving!
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R&S RTO Digital Oscilloscope
ı R&S RTO Product Details
# 1. High Signal Fidelity
# 2. Leading Acquisition Rate
# 3. Unique Digital Trigger
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#2 Market Leading Acquisition Rate
ı Sees up to 20x more than traditional oscilloscopes
ı => Detect and also
analyze rare signal
20x faster
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#2 Market Leading Acquisition Rate
R&S Enabler: RTC ASIC
ı An Acquisition ASIC with high integration level (14 million gates) and massive
parallel high-speed paths
20x parallel: acquisition block
ADC
8 bit, 10 Gbps
20x 8 bit, 500 Mbps
160x 500 Mbps
Memory
Acquisition
4x parallel: post-processing block
Post-Processing
Measurement, etc.
4x 8 bit
Memory
Display
R&S® RTC ASIC
90nm technology
14 M gates ASIC
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#2 Market Leading Acquisition Rate
Hardware Accelerated Analysis – Fast FFT
l
FFT based spectrum analysis:
powerful & user-friendly
l
HW overlapping FFT implementation =>
Very responsive and intensity modulated color display.
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Mask testing on FFT and
correlate with Time Domain
Mask violation -> Stop Acquisition
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R&S RTO Digital Oscilloscope
ı R&S RTO Product Details
# 1. High Signal Fidelity
# 2. Leading Acquisition Rate
# 3. Unique Digital Trigger
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#3 Unique Digital Trigger System
Challenges of Analog Triggering
ı Traditional: Analog trigger
=> has separate paths for signal and trigger different time-invariant
behavior of hardware components causes measurement errors
which cannot be compensated in real-time
ı Comparison of Digital and Analog triggering architecture
Traditional
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Innovative
Digital
Trigger
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FFT as Basis for EMI Debugging with Oscilloscopes
Conventional FFT Implementation on a Scope
Time Domain
Frequency Domain
Dt = 1/Fs
Fmax = Fs/2
x(t)
S(f)
t
Windowing
S(f)
FFT
f1 f2
f
Zoom
(f1…f2)
f1
f2
Display
Data acquisition
Df = 1/T
Record length T
Disadvantages:
 Time domain settings define frequency domain
 Zoom in frequency domain does not give more details
 Correlated Time-Frequency Analysis not possible
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f
FFT on the RTO
Spectrum Analyzer Use Model
ı Use model: Frequency domain
controls time domain

Time domain parameters (record-length / sampling
rate) automatically changed as necessary
Zoom happens here –
before the FFT!
ı Downconversion FFT (DDC) zooms into
500 MHz center, 10 MHz span:
frequency range before FFT
Fs = 1 GS/s vs 20 MS/s

Time
Domain
Largely reduced record length, much faster FFT
500 MHz center, 10 MHz span: 1 GHz vs 20 MHz
sampling frequency
Frequency
Domain
B=f2-f1
Fs=2B
HW Zoom (DDC)
x(t)
S(f)
LP
t
Data acquisition
Decimation
Windowing
FFT
f1
NCO
f2
Display
Df = 1/T
Record length T
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f
What if we combine time and frequency domain?
Overlap FFT comes into play
10GS/s
18.96ns/div
5 us/div
1898kSamples
Samples
500
Record length
FFT 1
Max frame count limit N = Nmax
Frame coverage up to here
FFT 2
1 FFT
~440
FFTs
(persistance
disabled)
FFT N
Advantages:
• Analyse time-dependend spectrum
• Conventional (non-overlapping) FFT looses
information due to windowing  overlapping allows
to capture everything
• Limit No of frames to ensure fast FFT processing
• Note: FFT processing starts from the left!
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Gated FFT in the RTO
Practical Time-Frequency Analysis
Gated FFT:
50% overlap (default setting)
|---------------------------------- One complete Time-Domain capture ----------------------------|
Key Feature for EMI Debug!
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FFT – Further Settings, Further Features
Max-Hold*,
Average, RMS
Spectrum Units
Correction factor
for a LISN
(frequency independent,
e.g. 10 dB in this case)
Multiple FFTs
Record length > 1 MS
Green: Max-Hold
Purple: Current spectrum,
intensity graded
*Note: Envelope = Max Hold
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What Accessory do we have?
Near-Field Probes
R&S ® HZ-15
Hameg HZ530
Hameg HZ540/550
E- and H-field
E- and H-field
E- and H-field
•
•
•
Small size
No battery
needed
Probe single
circuit lines
EUR 1.730,-
30 MHz – 1 GHz
Can be used down to 100 kHz
LISN
Note: No power
supply included
100 kHz – 1 GHz
EUR 788,-
R&S ENV216
1 MHz – 3 GHz
EUR 1.428,- / 1.848,-
Hameg HM 6050-2
Note: You need an
isolation transformer
for operating the LISN
EUR 2-4k
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EUR 1.038,-
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EMI Debugging: Equipment
R&S ® RTO
Near-field sniffer
Probes R&S ® HZ-15
E- and H-field
30 MHz – 1 GHz
Can be used down to 100 kHz
Optional:
R&S ® HZ-16
Preamplifier
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EMI Debugging: Equipment
R&S ® RTO
Near-field sniffer
Probes R&S ® HZ-15
E- and H-field
30 MHz – 1 GHz
Can be used down to 100 kHz
Optional:
R&S ® HZ-16
Preamplifier
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Frequency Analysis Debugging
EMI Test & Analysis
Magnetic field Probe
Electric field Probe
l Analyzing EMI Faults:
- Detecting possible signal problem due to EMI and sniff out the EMI source on
the DUT
l Locating EMI weak points:
- Injecting EMI to detect possible signal faults to identify weaker DUT location
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EMI Debug with Near-Field Probes
Important Settings
Parameter
Description
Record length
Ensure that you capture enough (>= 500 kSamples)
Vertical settings
1 – 5 mV/div, 50 W
Color table &
persistance
Easily detect and distinquish CW signals and burst
Max. Frame Count
Take care that you analyze the right part of the time signal
Signal zoom & FFT
gating
Easily isolate spurious spectral components in time
domain
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EMI voltage test: Basic test setup
>200 cm
reference ground
EUT
AN
> 200
test receiver
40 cm
30 to 40 cm
80 cm
>80 cm
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wooden
table
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Precompliance Measurements with a Scope ???
• Conducted Emission using LISN
• 9 kHz – 30 MHz
EN55015Q
• FSV trace 1 = Max hold / Pos Peak
RTO FFT1 = Normal mode
• FSV trace 2 = Clear Write / Auto Peak
RTO FFT2 = Envelope mode
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Precompliance Measurements with a Scope ???
• Conducted Emission using LISN
• 9 kHz – 1 MHz
EN55015Q
• FSV trace 1 = Max hold / Pos Peak
RTO FFT1 = Normal mode
• FSV trace 2 = Clear Write / Auto Peak
RTO FFT2 = Envelope mode
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FAQs … and Answers
Sensitivity
ı DANL at 500 MHz, 120 kHz RBW, 50 W
Receiver
DANL
RTO
~0 dBuV (1mV/div)1
ESR
-7 dBuV (with Preamp)2
ESCI
-4 dBuV (with Preamp)2
But:
A. RTO dynamic range
very limited compared to
EMI receivers
B. No preselection in RTO!
ı How to show on the RTO using the FFT


Note: Vertical Settings are 1mV/div, 50 W
Sampling rate>=2xBW of the scope! Otherwise aliasing will increase noise!
1Measured
2Datasheet
value
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FAQs … and Answers
Noise Figure
ı How to show on RTO






Vertical Settings
 1mV/div, 50 W
Enable FFT
Use RMS detector
Set center frequency
Set RBW to e.g. 1 MHz
Set unit to dBm
NF = Output noise – Input noise 
 RMS PowerdBm/RBW - (-174 dBm/Hz + 10xlog10 (RBW/Hz) ) =
= -98 dBm – 60 dB + 174 dBm = 16 dB
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FAQs … and Answers
What about …
ı Limit Lines?  Use the mask tool
Upper for limit line usage
Mask definition
in units of FFT
Upper region
mask acting
as limit line
Stop-on mask violation setting is very useful!
ı 6 dB EMI filter?

Not critical for precompliance, will change results only slightly.
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Use Cases
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EMI Debugging with Near-Field Probes
Use Cases
ı A) Debugging problems that occurred during compliance test
Noise from
power supply


CW Emission
Unknown broadband
noise peak
Identifying the location of the emission (down to signal paths)
Understanding signal behaviour to identify the source
ı B) Benchmarking EMI mitigation measures
Problem in compliance test
Check if shielding etc enough
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EMI Source Identification
Advanced debugging – Using the RTO for the far-field
EMI Receiver, Spectrum Analyzer
Oscilloscope
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Source: Weifeng Pai, David Pommerenke:
„EMI R&S
Failure
EMI debug using
RTOAnalysis Techniques: II: Joint
34 Time-Frequency Analysis“
EMI/EMC
Further Use Cases
C) Use near-field probes before compliance test

Only possible for EMC experienced design engineers
D) Near-field (small) EMI chambers

Near-field – Far-field transformation with oscilloscopes
 Only possible with two coherent channels
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EMI Debug
Customer Groups
ı EMC test house engineers



General EMI Debugging
Far-field and near-field measurement
Pulse calibration (ESD, EFT, Burst)
ı In-house EMC labs

See above
ı Design engineers
A) After failed compliance
B) Pre-Compliance
 Conducted emissions with LISN
 Radiated emissions when experienced enough
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Summary
USPs of the RTO for EMI Debugging
ı Sensitivity similar to EMI receivers
ı Capture intermittent events with stop-on-mask-violation in frequency domain

But, also time-domain trigger can help
ı Analyze in frequency domain after capturing (changing RBW etc)
ı Time-frequency correlation analysis (FFT gating)

Discover cause of emission in time signal
ı Flexible and easy-to-use FFT

Use it like a spectrum analyzer
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Thank You!
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