5/1/2015
Agenda
• Introduction/Overview
Improve EMC Compliance and
Precompliance Testing Throughput
with Time Domain Scanning
– What Is Time Domain Scanning
– Benefits of Time Domain Scanning
• Commercial
S
• MIL STD
• Issues/Concerns
Mark Terrien
Keysight Technologies
EMC Business Manager
– Using appropriate Dwell Time
– Complying with CISPR standards
– Preselector design
Factors Affecting EMC Test Times
Reduced EMC Test Time Improves
Revenue and Time-to-Market
Many factors affect both Compliance and
Precompliance test times
Compliance testing
‒ Chamber time is a limited resource
‒ Reducing test time improves efficiency
and profitability
•Device Under Test (DUT) setup time
•Receiver/ Spectrum Analyzer scan times
•Turntable and antenna movement times
Precompliance testing
•Suspect frequency analysis
‒ Rapid diagnosis of early designs speeds
time-to market, facilitating product sales
•Final measurement
Benefits Test Facilities and Manufacturers
Key Benefit: Reduced Test Time!
Time Domain Scan
(TDS)
• Collect list of suspect frequencies faster
• What is “Time Domain Scan”
-
Device
Under Test
A new way to do Frequency scanning
Swept scans, Stepped scans, now Time Domain scans
DUT
Emissions
• FFT-based
FFT based scan
-
•
uses ~ 90% overlap (in time) to ensure amplitude accuracy
for measurements of both CW and Impulsive signals
Allowed by CISPR 16, but not required.
• Benefits CISPR/FCC testing the most
- Internal Automotive industry testing specifications require
Time Domain
‒ Commercial testing requires turntable and antenna
optimization = more required scanning
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Classic Super Heterodyne Architecture
How Time Domain Sweep Saves Time
Only have to dwell for each
FFT BW (multiple RBWs)
Have to dwell at
each RBW
Reference
Oscillator
Step/Sweep
Generator
Synthesizer
Receiver FFT BW
(Acquisition BW)
Receiver
Resolution BW
amplitu
ude
RF Section
amplitu
ude
Video
Display
Analog IF
Local
Oscillator
RBW
Filter
IF
Gain
Log
Amp
Detector
Video
Filter
Log
Input
ADC
DownRF Input Pre-selector
conversion
Attenuator
5 or 10 dB Steps
Resolution BWs
Swept or Stepped
Frequency Scan
IF Gain Stages
Logarithmic Amps Detector
Variable bandwidth Selectable linear
filters used for
gains used to set
analysis
reference levels
frequency
frequency
Time Domain
Frequency Scan
Provide display
dynamic range
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Review: CISPR Radiated Measurement Methodology
All-Digital IF Architecture Facilitates TDS
Digital Conversion at IF
instead of Video
ADC
• Wider IF Bandwidths
• Powerful microprocessors
1. Fast Prescan to collect all suspect emissions
DSP
Log Amplification
RBW Filtering
Detection
Video Filtering
Averaging
Display Scaling
Signal Digitized
After RF DownConversion
2. Identify all emissions above target limit line
• Advanced DSP techniques
Downconversion
IF
IF
Filter Gain
3. Perform final measurement on individual signals
Video
Filter
Log
Amp
Log
i.
ADC
Find peak of signal, then make final measurement using
appropriate CISPR detector: Quasi-Peak, EMI-Avg, RMS-Avg
Pre-selector
Local
Oscillator
RF Input
Attenuator
Reference
Oscillator
TDS
i. Scan speed limited by CISPR
Helps Here
ii. Speed limit ensures you capture all emissions
iii. Typically use Peak detector, but can use CISPR detector
DUT
Emissions
Device
Under Test
Step/Sweep Generator
Video Display
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Test Time Reduction Example: CISPR*-based Test
1 to 4 m
above ground
plane
Long Dwell Time Plus Many Scans = Lots of Time
Test in vertical and
horizontal position
DUT
360 deg
Test in vertical and
horizontal position
1 to 4 m
above ground
plane
DUT
360 deg
3, 5 or 10 m
F
Frequency
Domain
D
i Scan
S
1. rotate DUT through 360°, scanning every 15° = 24 scans
2. test at 3 antenna heights (from 1– 4 meters)
3. both vertical and horizontal orientation
Purpose: identify peak emissions
3 or 10 m
CISPR Band
x3
30MHz–1GHz
x2
144 scans
Peak det. 10ms. dwell
RBW =120kHz
3 pts/RBW
~ 250 sec
150kHz–30 MHz
Peak det 100ms. dwell
RBW = 9kHz
2 pts/RBW
collect a list of suspect emissions for final measurement
* Example based on methodology defined in CISPR 16-2-3: Edition 3.1 section 7.6.6
144 scans
Typical Industry Swept
or Stepped times
660 - 750 sec
x
250 sec/scan
10 hours
Not counting antenna
and turntable positioning time
Keysight Confidential
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5/1/2015
Time Domain Reduces Scan Time
Time Domain Scan Offers
Significant Pre-scan
Time Reduction 1 to 4 m
Test in vertical and
horizontal position
above ground
plane
CISPR Band
Time Domain
Scan
Frequency Domain
Scan
Typical Industry
TDS times
Typical Industry
Scan times
~ .5 to 13 seconds
~ 250 seconds
MXE EMI
Receiver
DUT
360 deg
3 or 10 m
30MHz–1GHz
Peakk det.
P
d t 10ms.
10
d ll
dwell
RBW =120kHz
3 pts/RBW
Ti
Time
Domain
D
i Scan
S
CISPR Band
30MHz–1GHz
150kHz–30 MHz
Peak det 100ms. dwell
RBW = 9kHz
2 pts/RBW
144 scans
2
x ~250 sec/scan
Typical Industry
TDS Time
~ .1 to 11 seconds
Peak det. 10ms. dwell
RBW =120kHz
4pts/RBW
660 - 760 seconds
~ .5 to 13 seconds
10 hours
150kHz–30 MHz
Peak det 100ms.
dwell
RBW = 9kHz
4 pts/RBW
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4.8 minutes
~ .1 to 11 seconds
Not counting antenna
and turntable positioning time
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TDS Benefit for Testing Short Operation-Time Devices
Time Domain Scan and MIL STD 461
Example: Automotive Starter motors
• Operating for extended periods during
testing leads to overheating / thermal
damage
• Time domain scanning significantly
reduces test time.
Test in vertical and
horizontal position
No antenna height
variation
No device
rotation
DUT
1m
• MIL STD requires fewer scans: - no turntable rotation
- no antenna motion
• MIL STD specifies dwell times - 15ms/point for Freq > 1 kHz
• MIL STD 461F: no specific mention of TDS
• MIL STD 461G: proposed draft allows TDS
Time Domain Scan and MIL STD 461
Agenda
From recent draft of MIL STD 461G:
• Introduction/Overview
– What Is Time Domain Scanning
– Benefits of Time Domain Scanning
• Commercial
S
• MIL STD
• Issues/Concerns
– Using appropriate Dwell Time
– Complying with CISPR standards
– Preselector design
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Compliance with CISPR
TDS Dwell Time Must be Equal to or
Greater than the Emission Pulse Period
Correct Dwell Time
TDS Dwell Time = 20ms
Time Domain accepted as of CISPR 16-1-1:2010
1. Usable for pre-scan to create suspect list?
Emission
2usec
RF pulse
Yes – this is the key contribution
time
e
2. Usable for Final measurement?
Pulse Period 20ms
TDS Dwell Time = 10ms
TDS samples w/o pulse,
signal not displayed
Incorrect Dwell Time
Only if standard specifically references CISPR 16-1-1:2010
- currently, only CISPR 13 and CISPR 32
- other CISPR documents being adapted
Emission
2usec
RF pulse
time
Pulse Period 20ms
Compliance with CISPR (cont.)
2. Usable for Final measurement?
b) methodology must comply with recommended
measurement methodologies CISPR 16-2-3: 2010
RF Preselector Design Considerations
Issue: TDS Speed vs Susceptibility to Overload
TDS speed is a function of:
- width of IF acquisition bandwidth
- processing speed
- must monitor each suspect to ensure QP value is constant
- if QP not constant, must monitor for 15 seconds
needs
- if QP varies by
y more than +/- 2dB in 15 seconds,, signal
g
to be monitored for a longer period.
Single TDS sweep does not meet CISPR
requirements for Final Measurement
Preselection – What is it, Why use it?
Simplified
Simplified
Low band Path
(≤ 3.6 GHz in
X-series)
Input
RFLow
Preselector
pass
(bandpass
filter filters)
Low band
Down-conversion
Spectrum
EMI
Analyzer
Receiver
Front
FrontEnd
End
RF Input
Attenuator
(Keysight, R&S, etc.)
High band Path
YIG preselector filter
(microwave bands)
~ 60 MHz 3dB BW
Microwave band
Down-conversion
RF Preselector
Acquisition bandwidth limited by RF
Preselection bandwidth
Wider Preselector Filters Enable Faster Scanning Speed
Preselector
Input
• Provides Dynamic Range to measure CISPR pulse / meet CISPR 16 requirements
Display
freq
Wider Preselector Filters enable…
Narrow Preselector Filters
Acq.
BW
freq.
– critical piece of a CISPR-compliant EMI receiver
– reduces broadband energy to 1st Mixer
– measure with less input attenuation
Acquisition
BW
A/D
Micro
Processor
• Bank of Filters before first mixer (fixed or tuned)
• Helpful when measuring large impulses (which have wideband spectral energy)
DownConvert
Wide Preselector Filter
• Use of Wider Acquisition BWs
• Fewer Acquisitions for a
given frequency range
• Faster Scanning
..BUT there is a Problem….
Acquisition
BW
freq
.
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Compare Two Receivers: Wider Filters Overload First
Wider Preselector Filters =
Reduced Impulse Overload Protection
Receiver 1: Wide Preselector Filters
Receiver RF Section
Input pulse
Vp
Wide BW
Input pulse
Vmax = Vp Τ BWi
Impulse BW
BW i
Vp
RF Input
Attenuator
Vp1
Overloads
Receiver 1
Vp1
RF
Preselector
Downconversion
Receiver 2: Narrow Preselector Filters
RF Input
p
Attenuator
Τ= pulse
width
Τ= pulse
Downconversion
RF
Preselector
Narrow BW
width
Max Mixer input voltage is proportional to Preselector Filter Bandwidth
RF Input
Attenuator
Receiver with Wider Preselector filters will Overload earlier for same
pulse
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RF
Preselector
Vp2
Downconversion
Vp2 < Vp1
Vp2
does not
overload
Receiver 2
Wider Preselector filters can result in
lower impulse dynamic range
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Compare Two Receivers: Wider Filters Require More
Input Attenuation to Eliminate Overload
Receiver 1: Wide Preselector Filters
Input pulse
Vp
Att1
RF Input
Attenuator
Wide BW
Rx 1 requires
larger Att1 to
eliminate
overload!
Vp1
Downconversion
RF
Preselector
Receiver 2: Narrow Preselector Filters
Τ= pulse
width
Att2
Narrow BW
RF Input
Attenuator
Vp2
RF
Preselector
Att1> Att2
Rx1 sensitivity
now worse than
Rx2
Downconversion
Wider Preselector filters can result in worse sensitivity
Summary
‒ Time Domain significantly reduces test time
• CISPR
• Accepted by CISPR for use in receivers
• Greatest value is in Prescan
• MIL STD 461F
• Not specifically called out in 461F
• Allowed in 461G
‒ Critical to use appropriate dwell time
• Dwell time must be at least 1/ (DUT Pulse repetition rate)
• Needed to ensure emission during Dwell period
‒ Be aware of lower overload thresholds when
using receivers with wide preselector filters
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N9038A MXE EMI Receiver Provides
World-Class EMI Measurement Capability
• Commercial and Military Compliance
- CISPR 16-1-1: 2010, MIL-STD-461F
- all required detectors, bandwidths
With Optional
Time Domain
Scan
Keysight X-Series Signal Analyzers +
N6141 EMC Application: Powerful
Precompliance Tools
PXA N9030A
• Broad Frequency Coverage
- 20 Hz to 3.6, 8.4, 26.5 and 44 GHz
- tunable to <10 Hz
With Optional
Time Domain
Scan
N6141 A
EMI Application
MXA N9020A
• Excellent accuracy
- 0.5 dB @ 1 GHz
• Excellent sensitivity
EXA N9010A
• Broad Range of Price + Performance Levels
- DANL = -166 dBm @ 1 GHz w/ NFE
- Built-in standard preamplifier
• Powerful Diagnostic Tools
CXA N9000A
• Common User Interface with MXE
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5/1/2015
Questions?
Thank you for your attention!
Thanks for attending!
Don’t miss our Test Bootcamp!
November 12, 2015
www.emclive2015.com
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