RF Probing - PacketMicro Inc.€¦ · RF Probing Tips •Good contact of both probe tips with the DUT is essential to accurate calibration and measurements. •Using a good microscope

PacketMicro, Inc. 1900 Wyatt Drive, Suite 9, Santa Clara, CA 95054 www.packetmicro.com

RF Probing With

Anritsu MS46522A VNA

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Outline

• Why RF Probing Page 3 – 4

• RF Probing Tips Page 5

• RProbe Summary Page 6 - 9

• Tools: Probes, Positioners, and Microscopes Page 10 - 12

• Probe Planarization with Mylar Page 13 - 17

• Probe Planarization with TCS60 Page 18 - 19

• SOLT Calibration Page 20 - 37

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3

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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4

Measurements of RF Low-Pass Filter

RF probe is almost as good as SMA connector!

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SMA-SMA

RProbe - SMA

Soldered Cable - SMA

5

RF Probing Tips

• Good contact of both probe tips with the DUT is essential to accurate calibration and measurements.

• Using a good microscope is very important.

• Affixing a piece of Mylar tape to the PCB can guide the probe planarization process.

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RProbes

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Features • High Bandwidth: DC to 12 GHz • Low Insertion Loss: < 3 dB @ 12 GHz • Ruggedness: Beryllium Copper tips • Probe-tip Calibration: TCS 50 Cal Substrate • High Repeatability: No moving part RProbe Part No. • RP-GR-121502 – 12 GHz, 0.2 mm/08 mil pitch • RP-GR-121504 – 12 GHz, 0.4 mm/16 mil pitch • RP-GR-121505 – 12 GHz, 0.5 mm/20 mil pitch • RP-GR-121508 – 12 GHz, 0.8 mm/32 mil pitch • RP-GR-111510 – 12 GHz, 1.0 mm/40 mil pitch • RP-GR-111512 – 12 GHz, 1.2 mm/48 mil pitch

0.5 mm 0.8 mm 1.0 mm

Un-calibrated S21 for 3 probe pitches Un-calibrated S11 for 3 probe pitches

Thru Measurement with Probe-Tip Calibration

Calibrated at SMA connectors

Calibrated at probe tips

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Thru Measurement



(MHz)

(MHz) (MHz)

(MHz)

S11 Measurements of a 50Ω Standard

Probe-tip calibration allows accurate, repetitive measurements.




Two-Port Probe-Tip Calibration Setup

Precision TP300 Positioners with RProbes


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Tools - Accessories

Optical Microscope (~ 90 x magnification)

TCS60 Calibration Substrate

Mylar Tape

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 the probe tips well.

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TP300 Precision Positioners (XYZθ)

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Microprobe on TP300

RProbe on TP300

• Accurate (100 TPI) • Ergonomic • Perfect for Microprobe

and RProbe

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TP60 Flex Positioners (XYZθ)

(Planarization knob)

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• Accurate (100 TPI) • Coarse and fine adjustment

without tool

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Probe Planarization with a Mylar Tape

Step 1:

Place the a piece of Mylar tape close to the test pad, so that they have the same reference surface.

Mylar Tape

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RF Probe (tips not touching)

Test Pad

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Signal tip touches down first

Step 2:

Land the probe tips on the tape and observe the probe-tip footprint. Above image shows that signal tip touches the surface first.

Signal GND

Mylar indentation caused by signal tip

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GND tip touches down first

Step 3:

Adjust the planarization knob on the positioner to lower the GND tip. Above image shows that GND tip touches the surface first.

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Signal GND

Mylar indentation caused by GND tip

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Both tips touch down simultaneously

Step 4:

Adjust the planarization knob on the positioner to land both probe tips. Above image shows the two probe tips touch the surface evenly.

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Signal GND

Mylar indentation caused by both tips

TCS60 on Plastic Carrier

• Use the Mylar tape on the back of the plastic cap for probe planarization

• Place TCS60 on top the plastic cap and perform SOLT calibration

• Remove the TCS60 and start probing


Use Mylar for Probe Planarization

Use TCS60 for SOLT Calibration

Use Probe Marks on TCS60

Left touching Right touching

Only one tip touches; need adjustment!

18 www.packetmicro.com

Use VNA to Verify Probe Contacts

Both tips touching

• Both tips leave light probe marks

• 180° Phase changed in S11 or S22

Short


2-Port Probe-Tip Calibration


• Reflection calibration (Short, Open, Load calibration for two ports)

• Transmission calibration (Thru calibration)

Thru

G S G S

Open Short

Probe-tip Calibration with MS46522A

1. Load probe-dependent TCS60 cal kit file (e.g. TCS60_08mm.ccf) into VNA

2. Go to “Edit Cal Params” page 3. Select TCS60 cal kit for Test Port 1 and Test Port 2 4. Enter Thru Coefficient 5. Perform SOLT calibration


Load Calkit File

1) Calibration -> Calkit Options -> Load Kit/Charac 2) Browse -> Load TCS60_XXmm.ccf


Edit Cal Params

1) Calibration -> Manual Cal -> 2-Port Cal -> Modify Cal Setup -> Edit Cal Params.


Select Cal Kit for Test Ports

1) Edit Cal Params -> Select TCS60_XXmm (M)


Verify CalKit

1) Verify the TCS60_XXmm coefficients, if necessary


Enter Thru Coefficient

1) Check the TCS60_XXmm (M) is selected on Test Port 1 and Test Port 2

2) Use Thru calculator to enter length


Thru calculator

Enter Thru Coefficient – cont.

1) Enter length (5.8 ps) and dielectric constant (9.8)


Verify CalKit Before Performing SOLT

1) Check the TCS60_XXmm (M) is selected on Test Port 1 and Test Port 2

2) Check Thru is entered


Set S11 to Display Phase Before Cal

1) Response -> S11 2) Display -> Trace Format -> Phase 3) Marker -> Marker 1 (ON)


Probe-tip Calibration - Short

• Calibration -> Manual Cal -> 2-Port Cal -> Port 1 Reflective Devices

• S11 Phase Changes 180° when both tips touching


Short Pattern

Probe

Probe-tip Calibration - Open

• Land the probe tips on “Open” pattern • S11 Phase should not change • Click Open


Open Pattern

Probe-tip Calibration - Load

S11 phase for Load


• Land the probe tips on “Load” pattern • Click Load

Load Pattern

Probe-tip Calibration – Port 2


• Back-> Port 2 Reflective Devices • Click “Open” and VNA automatically displays S22 • Perform SOL for Port 2

Probe-tip Calibration – Thru


• Back-> Thru/Recip. • Make sure both probes make good contact

Both probes make good contact

2-Port Calibration Completed


• Back-> Done • Cal Status becomes “ON”

S21 and S12 should be close to 0 dB

2-Port Measurement of a RF Filter


TDK 2.45 GHz Low Pass Filter (P/N: DEA102500LT-6307A1, Size 0402)

37

Thank You

Contact: [email protected] Office: 408-675-3900

RF Probing with Ease!

Rugged RF probes up to 12 GHz

Probe-tip calibration with TCS60 substrate

Precision TP300 and TP60 Positioners (XYZθ) Don’t forget to use Mylar tape for planarization

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Documents

RF Probing - PacketMicro Inc.€¦ · RF Probing Tips •Good contact of both probe tips with the DUT is essential to accurate calibration and measurements. •Using a good microscope