Post on 17-Jul-2020
PacketMicro, Inc.2312 Walsh Avenue, Suite A, Santa Clara, CA 95051 www.packetmicro.com
RF ProbingWith
Keysight E5071C VNA
Outline
• RF Probing Examples Page 3 – 7
• S-Probe Overview Page 8 - 11
• RF Probing Tips Page 12
• Tools: Probes, Positioners,
and Microscopes Page 13 - 15
• Probe Planarization with Mylar Page 16 - 20
• Probing DUT on Uneven Surfaces Page 21 - 23
• RF Probing in a Box Page 24
• Import TCS60xx.CKX file Page 25 - 28
• SOLT Calibration Page 29 - 38
• Manual Entry of TCS60 into VNA Page 39 - 42
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Why RF Probing?
• Necessity: Constant shrinking size of circuit
components makes soldering semi-rigid RF cables to test gigahertz circuits impractical.
• Accuracy: RF probes and calibration substrates
allow engineers to perform probe-tip calibration for accurate, repetitive measurements.
• Productivity: Any engineer can do RF
measurements in minutes without being a master in soldering semi-rigid cable
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Measurements of RF Low-Pass Filter
RF probe is almost as good as SMA connector!
SMA-SMA
S-Probe - SMA
Soldered Cable - SMA
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RF Fixture Testing
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S21
-1.31 dB @2.41GHz
RF Module Testing
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RF Antenna Testing
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S-ProbeFeatures• High Bandwidth: DC to 20 GHz• Low Insertion Loss: < 3 dB @ 20 GHz• Ruggedness: Beryllium Copper tips• Probe-tip Calibration: TCS 60 Cal Substrate• High Repeatability: No moving part
S-Probe Part No.• SP-GR-2015025 – 20 GHz, 0.25 mm/10 mil pitch• SP-GR-201504 – 20 GHz, 0.4 mm/16 mil pitch• SP-GR-201505 – 20 GHz, 0.5 mm/20 mil pitch• SP-GR-181508 – 18 GHz, 0.8 mm/32 mil pitch • SP-GR-181510 – 18 GHz, 1.0 mm/40 mil pitch• SP-GR-161512 – 16 GHz, 1.2 mm/48 mil pitch
Un-calibrated S21 for 3 probe pitches Un-calibrated S11 for 3 probe pitches
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Thru Measurement with Probe-Tip Calibration
Calibrated at SMA connector
Calibrated atprobe tips
Thru Measurement
Calibrated at probe tips
Calibrated at SMA connectors
(20 GHz)
(20 GHz)
(20 GHz)
(20 GHz)
Probe-tip calibration (0.5 mm S-Probe)
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S11 Measurements of a 50Ω Load
Probe-tip calibration allows accurate, repetitive measurements.
Calibrated at SMA connectors
Calibrated at probe tips(0.5 mm S-Probe)
(20 GHz)
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2-Port Probe-Tip Calibration Setup
Precision TP300 Positioners with S-Probes
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Probe Planarization Tips
• Good contact of both probe tips with the DUT is essential to accurate calibration and measurements.
• Mylar tape provides leveling guidance on flat, even surface (bare PCB).
• Color marker helps on uneven surface (solder bump).• A good microscope is important. You might damage
the probe if you cannot see its tips well.
Tip skid marks
Mylar indentation caused by both tips
GND
Signal
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Tools - Accessories
Optical Microscope(~ 90 x magnification)
TCS60CalibrationSubstrate
MylarTape
USB Digital Microscope(~ 90 x magnification)(Make sure to use a long working range (5 cm @ 90x) microscope!)
• Using a good microscope is essential.
• You might damage the probe if you cannot see its tips well.
Fine-tipSharpie pen
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Precision Positioner – TP250
▪ Precise: XYZ stage (100 TPI, 2.5 μm resolution)
▪ Versatile: detachable θ stage
▪ Easy: lockable magnetic base14
TP150 Precision Positioners (XYZθ)
(Planarization knob)
• Accurate (100 TPI)• Coarse and fine adjustment
without tool
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Probing Test Pads on Even Surfaces
• Use the Mylar tape on the back of the plastic cap for probe planarization by observing the indentation caused by the tips.
• Remove the plastic cap and perform probing• Affix a Mylar tape next to test pads if there is not
enough space for placing the plastic cap.
MylarMylar indentation caused by both tips
GND
Signal
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Signal tip touches down first
Step 1:
Land the probe tips on the tape and observe the probe-tip footprint. Above image shows that signal tip touches the surface first.
GNDSignal
Mylar indentation caused by signal tip
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GND tip touches down first
Step 2:
Adjust the planarization knob on the TP150 positioner to lower the GND tip. Above image shows that GND tip touches the surface first.
Mylar indentation caused by GND tip
GNDSignal
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Both tips touch down simultaneously
Step 3:
Adjust the planarization knob on the positioner to land both probe tips. Above image shows the two probe tips touch the surface evenly.
Mylar indentation caused by both tips
GNDSignal
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Use VNA to Verify Probe Contacts
Both tips touching• Both tips leave light
probe marks• VNA Smith Chart
shows “Short”
Short
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Probing Test Pads on Uneven Surfaces
• Color solder bumps with a Sharpie• Use the probe skid marks to confirm good tip
contact• Clean up the solder bumps with industrial alcohol
after probing
Tip
sk
id m
ark
s
Fine-tipSharpie
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Use Probe Skid Marks on Solder Bumps
GND Tip Mark
Left GND tip touches down first
Signal Tip Mark
Right signal tip touches down first
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Both Tips Touch Down Simultaneously
2 Tip Marks
Both tips touch down simultaneously
Clean up solder bumps with industrial alcohol after probing
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RF Probing in a Box
“RF Probing in a Box” ▪ 2x TP150 positioners ▪ 1x FP40 positioner▪ 4x PH100 PCB holders
▪ 1x AM4115ZTL Dino-Lite microscope▪ 2x SP-GR-xx15yy Probes ▪ 1x TCS70 Cal substrate
TP150 TP150
FP40
PH100
AM4115ZTL
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2-Port Probe-Tip Calibration
• Import TCS60 coefficients (probe dependent) into VNA(TCS60_05MM.ckx, TCS60_08MM.ckx, TCS60_10MM.ckx)
• Perform 2-port SOLT calibration
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Import TCS70xx.CKX file
Press CAL button and choose an unused “User” kit ->
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Import TCS60 TCS60xx.CKX file - Cont.
Press “Import Cal Kit” soft key ->
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2-Port Calibration with TCS70
• Reflection calibration (Short, Open, Load calibration for two ports)
• Transmission calibration (Thru calibration)
Thru
G SGS
OpenShort
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Reflection Calibration - Short
• Perform Short first to verify probe planarization
Short
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Reflection Calibration - Open
Open Pattern Open
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Reflection Calibration - Load
Load Pattern
Load
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Transmission Calibration - Thru
• Make sure that both probes touch down
GND SIG
Thru standard on TCS60Two probes measure the Thru standard.
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Transmission Calibration - Thru
• Make sure that both probes touch down
At least one probe does not touch down
Both probes touch down
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Correct Thru Calibration
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Incorrect Thru Calibration
E5071 Screen ShotDuring Calibration
S21 & S12 < -12 dB
S11 & S22 > -8 dB
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Completion of SOLT Calibration
• S11 and S22 should be only a dot on the Smith chart
• S21 and S12 should be a flat line
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Completion of SOLT Calibration – cont.
Completion of a good SOLT calibration
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Appendix – Manual entry of TCS60
You can manually enter the coefficients of TCS60 Cal Kit by following these steps:
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Enter SOLT – cont.
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Specify CLS - Short
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Specify CLS – Open, Load, Thru
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Thank You
Contact:support@packetmicro.com Office: 408-675-3900
We help make your high-speed probing
projects successful !• Flex Probe Stations
• Rugged 20 GHz RF Probes
• Laboratory Rental
• Engineering Services
• Signal Integrity Consulting
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