5/14/2012
© Agilent Technologies, Inc. 2012 1
Copyright © 2012 Agilent Technologies
Millimeter Signal Measurements:
Best Practices, Solutions, and
Accuracy
Ben Zarlingo Product Manager, Signal Analysis
Microwave & Communications Division
Copyright © 2011 Agilent Technologies
© Agilent Technologies 2012
Agenda
Millimeter Measurements Discussion
– Information
– Best Practices
– Optimizing Performance
Special Hazards, Problems
Choosing Measurement Tools, Alternatives
Millimeter Signal Measurement Solutions
References, Resources
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What is Millimeter-Wave?
Wavelengths ~≤ 10 mm, f ~≥ 30 GHz
Where Everything Gets
– Difficult
– Small
– Expensive
– Lossy
– Delicate
– Inflexible
– Banded (if not narrowband)
Graduate Work for the Electrical Engineer
Commercial/Consumer: 60 GHz Wireless HD
$600 Transmitter + Receiver $300
$180
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Millimeter Performance Expectations
Performance Generally Less Ideal
– Harmonic architecture (phase noise, conversion loss, etc.)
– Path/insertion losses, impedance mismatches
– Preselector filtering
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New Calc. Method for Mismatch Uncertainty
Mismatch Uncertainty typically
dominates
Better understanding, verification of
probability distributions
Rayleigh model is an excellent fit,
provides more accurate but still
conservative estimates of uncertainty
due to mismatch
Result: Lower Uncertainties due to mismatch
by factor of 3 to 6
AN 1449-3 Power Measurement Uncertainty
Per International Guidelines (updated April 2011)
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Better Calculations Indicate
a Rayleigh Distribution
Probability density of the magnitude of the reflection
coefficient is Rayleigh distributed if the probability
density of both complex parts is Gaussian distributed
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Validating Assumptions
with Real World Examples
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Importance of Cables, Connectors
Influence of Materials, Structures, Geometries
Amplitude, 30-50 GHz
– Dropouts due to moding* – Amplitude, phase errors
– Errors with 3.5mm also, though perhaps more repeatable
– Error < 2dB in this example
• Good enough?
• Repeatable enough?
Performance Gain from cables may be very Cost-Effective
2.4 mm
SMA
*Moding: Excitation of the first
circular waveguide propagation
mode in the coaxial structure
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Plastic vs. Air Dielectric
PTFE vs. Air, Beads
– Air for metrology grade & many instrumentation grade
Many Other Tolerances & Construction Differences Usually
Accompany Dielectric Change
SMA
3.5 mm
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Use A Torque Wrench for Consistency
“Wrench Lift Stress” is a special concern with several
devices connected or a long device or adapter(s)
Lift
Angle between
wrenches should
be less than 90
deg
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Torque Values & Wrench Sizes
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Torque Problem Example
Loose Cable Amplitude
Error
– Significant for you?
What if it is variable and
inconsistent?
Phase Variability
Sufficient Torque
– Enough torque to properly mate
surfaces and to produce a strain
that will prevent loosening due
to vibration and/or thermal
cycling
– Not enough to damage or distort
connectors, changing geometry
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Connector Grades
Metrology Grade – Highest precision, performance, repeatability
– Often slotless female center conductors (repeatable, lower inductance)
– Often used in calibration/verification kits
– Expensive, long life
PSC = Precision Slotless Connector – Typically metrology grade; PSC versions available for 3.5mm, 2.4 mm
Instrument Grade – Excellent repeatability, long life
– Often slotted female center conductors
General Purpose or Production Grade – Typical on components, cables, microstrip
– Inspect before connecting to better grades (analyzers), use adapter
– Limited connection cycles
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Connection Consistency
Consistent Connections Improve Repeatability – Same Cables (cable loss may be more than 3 dB/meter at 50 GHz)
– Same connectors, adapters
– Same cable routing
Every Connection & Transition is Imperfect – Insertion loss (one adapter = up to 1 dB loss at 50 GHz)
– Impedance change
– Bending can change cable characteristics
– Consider semi-rigid cable
Analyzer Accuracy is Improving Smaller Errors Matter
Repeatability may be More Important than Absolute Accuracy
Standardize on Highest Frequency Connectors? – Consistency, but slightly higher loss at lower frequencies
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mm-Frequency Connectors and Intermating
24 pt level 1
– 20 pt level 2
• 18 pt level 3
http://na.tm.agilent.com/pna/connectorcare/What_mates_with_what.htm
Uses a plastic (PTFE) dielectric
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Torque for Intermating
Proper Torque for Intermating Can Depend on Gender
– Example 1: A 56 N-cm. torque wrench should be used to connect male
SMA connectors to either 3.5-mm or 2.92-mm (K) connectors
– Example 2: A 90 N-cm torque wrench should be used to connect male
3.5-mm or male 2.92-mm connectors to mating female connectors
including SMA
Precision Connectors use Higher Torque
– Use lower torque with SMA SMA
– Use lower torque with male SMA male precision
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Important Lower Frequency Connections
in a High Frequency System
Connectors Make a Difference in Some Low Frequency
Measurements!
3.5 mm or SMA to BNC
Precision BNC connections on Oscilloscope
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Coax & Waveguide Comparison
Flexible
Wide frequency range
Easy to change routing
Light weight
Can carry DC bias
Can be less expensive
Good match for component meas.
Disadvantages
– Lossy, increasing with frequency
– Can be delicate
– Limited power handling
Low loss
High power handling ability
Mechanically durable
Disadvantages
– Inflexible
– May need custom construction (expensive)
– Time delays for construction and reconfiguration
– Frequency range ≤ 1 octave
– Transitions needed to connect to analyzers, other coaxial elements
Coax Waveguide
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Hardware Features & Signal Processing
Improve Performance
Low Noise
Path
Noise Floor
Extension
19
• Standard
• With LNP
• With NFE
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Agenda
Millimeter Measurements Discussion
– Information
– Best Practices
– Optimizing Performance
Special Hazards, Problems
Choosing Measurement Tools, Alternatives
Millimeter Signal Measurement Solutions from Agilent
References, Resources
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Beware of DC at Analyzer Input
Millimeter Agilent PXA, PSA Have No DC Block
Why? Internal DC Block Would Compromise Performance
Add External DC Block if Needed
Front Panel Male Connector
Protects Analyzer
– Discourages direct mating with
typical coaxial male connector
– Encourages use of connector saver
– Male connector more durable,
less likely to be damaged from
improper mating
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Adapters as Connector Savers
Connectors are “Consumables” with a Limited Lifetime
Non-Millimeter Instruments Typically use Female Front Panel Connector – Use to mate male cables with
male analyzer connector
– Consider other types as needed in your application
Note “Flats” for Wrenches to Prevent
Connector Rotation
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Damage Hazard: Non-Captive SMA Nut
Danger from SMA Male to 2.4 mm and 1.85 mm Female
3.5 mm to 2.4 mm adapter
3.5 mm end 2.4 mm end
SMA with non-captive nut
and extended center pin SMA with non-captive nut can be inserted into
2.4 mm
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Electrical Damage
High Frequencies Small Size Electrically Delicate
Burnout from Excess Power
Burnout from Source Transient
Static Zap
Detecting Damage (other than outright failure)
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Microphonics, Other Movement
Phase Noise, Close-In Modulation
Can Affect Analyzer, Connections, DUT
Mitigating Microphonics
– Separate table, mounting
– Use isolating feed/pads/mounts
– Stabilize or support cables, waveguide
– Use phase-stable cables
Vibration, Thermal Cycling may Loosen Connections
– Torque check as part of measurement routine
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Alignment, Calibration, Correction
Calibration: Initial & Periodic Adjustment, Verification – Factory, service center, calibration lab
Alignment: Frequent Self Adjustment – Automatic adjustment compensates for temperature, drift, aging
– Alignment can affect dynamic range
Correction/Compensation – Often included in demodulation operations
– Substitution (power meters, etc.)
– May be only practical way to dramatically improve accuracy
– Enter parameters in analyzer for front-panel operation
– May be manually cumbersome or need switching
Perform Alignments Frequently and Whenever Measurement conditions Change – Temperature sensitivity generally goes up with frequency
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Preselector Centering, Tuning
YTF Preselector (Filter)
– YTF operates open-loop
– Preselector tuning is
characterized automatically by
analyzer for full frequency
range
– Centering performed by
analyzer, very brief operation
– Perform centering for best
amplitude accuracy at a single
frequency
– Centering is initiated by user;
not part of normal alignment
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Preselector Affects Wideband Signals
Solution: Preselector Bypass
“Microwave Preselector Bypass”
Hardware Option
Removes YIG-Tuned Preselector Filter from
Measurement Path
– Essential for wide-bandwidth measurements
– Removes preselector insertion loss but passes
wideband noise; effect on analyzer DANL
is variable
– May allow other signals into measurement
– Can tune to signal with preselector in place
and then bypass
Preselector
Bypass Path
Norm
Bypass
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Choosing Measurement Tools
Where Should the First Mixer Be?
Why Not a Millimeter Oscilloscope?
Recent Developments in Performance, Functionality
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Millimeter Signal Measurement Solutions
5/14/2012
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External Mixing and Downconverters:
Analyze Signals to 750 GHz
New M1970 V/W
50-110 GHz
11970 Series
millimeter mixers
18 GHz to 110 GHz
≥ 110 GHz
Legacy Mixers NEW
Smart Mixers
Third Party Mixers
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External Mixing Bypasses
First Internal Mixer
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Agilent 11970 Series Harmonic Mixers
Connection Detail
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Basic Setup: External Mixer
34 34
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Conversion Loss Corrections
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M 1 9 7 0 V / W W A V E G U I D E H A R M O N I C M I X E R S Mixer Products, No Signal ID
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M 1 9 7 0 V / W W A V E G U I D E H A R M O N I C M I X E R S Signal ID: Image Shift
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M 1 9 7 0 V / W W A V E G U I D E H A R M O N I C M I X E R S Signal ID: Image Suppression
Note: Unstable signals may be removed
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WAVEGUIDE HARMONIC MIXERS
M1970V: 50 - 75/80 GHz
M1970W: 75 - 110 GHz
Ease-of-Use & Simplification of Test Setup
– USB plug-and-play
• Auto detection & parameter download
• Auto configure frequency range, harmonic number
• Auto amplitude correction
• Auto LO power adjustment with
up to 3m cable loss
• Single coaxial IF/LO interface
Improved Performance and Accuracy
– Improved conversion efficiency to 25 dB
• Better DANL by 6 dB
• Enhanced Calibration Accuracy to+/- 2.2dB
39
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40
External Mixer Performance & Functionality
Extend to 325 GHz and
beyond
• Supported measurements
•Spectrum analysis
•PowerSuite
•N9068A phase noise meas. app.
• Supported external mixers
•M1970V and M1970W
•11970 Series
•Virginia Diodes Inc.
•OML Inc.
•Farran Technology Ltd.
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Why Not a Millimeter Oscilloscope?
Indeed, Why Not?
One box solution
Very wide bandwidth
Multiple simultaneous channels
Baseband coverage
Good in-band performance
VSA functionality
– Expensive
– Limited dynamic range
– Very wideband, not internally filtered
– Very large sample count for some measurements
• Decimation, resampling, digital LO performed by DSP
• Some demodulation measurements can be slow
Agilent 90000 X-Series Oscilloscopes
True 33 GHz analog bandwidth
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Dedicated Upconverters &
Downconverters for Wideband 60 GHz
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802.11ad Test Block Diagram
WiGig & WiHD
43
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Dedicated Upconverters & Downconverters
Advantages
High sensitivity/ low conversion
loss
– Suitable for antenna applications
– Useful for applications where devices
do not have external connectors
Wide Modulation bandwidth
Flexible cabling to couple directly
to signal or device under test
Disadvantages
Banded, limited operating
frequency
Require external local oscillators
Not preselected
Not an off-the-shelf product
Expensive compared to external
mixers
Not a source or analyzer
– Typical application includes signal
generator, modulation source,
separate low frequency or baseband
analyzer & VSA software
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PXA as a Millimeter Downconverter PXA Downconversion Extended to 50 GHz
Adjustable IF Outputs
Fast Video Out, Including Preselector Bypass
Fast Log Video Out
Temporal analysis of radar pulses and pulsed EW RF
Trigger other devices
Wideband Output, 600-800 MHz Bandwidth
Digitize with Oscilloscope or Other
Analyze with 89600B VSA
50 GHz
Infiniium
DSO90204
2.5 GHz + VSA
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High Band IF Output Examples Millimeter Frequencies, Wide Bandwidths
Preselector Bypass On/Off
600 MHz BW, 5
dB Flat
Offset to CF 500 MHz
800 MHz BW, 8 dB Flat
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PXA Fast Log Video Output
Connect to Oscilloscope for Temporal Analysis
of Radar and EW Pulsed RF
Use Fast Video Out to Trigger Other Equipment
Select from Front Panel:
• Tunable IF Out
• 2nd IF Out
• Trigger Out
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Fast Video Output, Preselector Bypass
High Band Example,
Low Band Several ns slower
– Freq = 9.6 GHz
– PW = 100 ns
– Span = zero-span
– Sweep = single
– Path = Bypass
– Rise time = 13.91 ns
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Additional Information
Fundamentals of RF and Microwave Power Measurements (part 3) Power Measurement Uncertainty Per International Guidelines AN-1449-3, April 2011 http://cp.literature.agilent.com/litweb/pdf/5988-9215EN.pdf
Average Power Sensor Uncertainty Calculator http://www.home.agilent.com/upload/cmc_upload/All/Average_Power_Sensor_Uncertainty_calculator_Rev6.xlsx
Coaxial Connector Overview www.home.agilent.com/upload/cmc_upload/All/CoaxialConnectorOverview.pdf
What Mates With What http://na.tm.agilent.com/pna/connectorcare/What_mates_with_what.htm
Connector Grades http://na.tm.agilent.com/pna/connectorcare/Connector_Grades.htm
Intermateability of SMA, 3.5 mm AND 2.92 mm Connectors
Microwave Journal (Cables & Connectors Supplement) 3/2007, available at www.gore.com
Connector Care Quick Reference Card http://cp.literature.agilent.com/litweb/pdf/08510-90360.pdf
Principles of Connector Care http://cp.literature.agilent.com/litweb/pdf/5954-1566.pdf
External Waveguide Mixing and Millimeter Wave Measurements with Agilent PSA Spectrum Analyzers (app-note 1485) http://cp.literature.agilent.com/litweb/pdf/5988-9414EN.pdf
Copyright © 2011 Agilent Technologies
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Questions?
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11970 Waveguide Harmonic Mixers
Model Freq
(PSA)
N
(PSA)
LO
(PSA)
Max
LO
(LPF)
Freq
(PXA)
N
(PXA)
LO
(PXA)
11970A 26.5-40 8- 3.35-
5.04 5.2
26.5-30.9 6- 4.47-5.2
30.1-40 8- 3.8-5.04
11970Q 33-50 10- 3.33-
5.03 5.2
33-41.3 8- 4.17-5.2
37.7-50 10- 3.8-5.03
11970U 40-60 10- 4.03-
6.03 6.2 40-60 Same Same
11970V 50-75 14- 3.59-
5.38 5.6
50-66.9 12- 4.19-5.6
52.9-75 14- 3.8-5.38
11970W 75-110 18- 4.18-
6.13 6.2 75-110 Same Same
•11970 mixer models selectable in UI (11970A/Q/U, etc.), for parameter setup
• Mixer conversion loss data at different harmonic numbers is provided on CD
• External diplexer required with PXA (ex. N9029AE13)
• PXA does not support preselected mixers
11970 Series
millimeter mixers - 18
GHz to 110 GHz,
11970K not supported
PSA/PXA use same harmonic numbers with same conversion loss data
PSA/PXA use different harmonic numbers, require different conversion loss
data