Dual-Band Probes with Broadband Diplexers

for 2-Port Measurement up to 170 GHz

Florian Boes and Georg GramlichKarlsruhe Institute of Technology, Germany

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Outline

Why including Diplexers in RF Probe

Motivation

Diplexer TheoryWorkflow

Filter Design

Scale Down Prototype

Measurement Example

Verification

Conclusion Outlook

Roundup

3

Motivation• Limited measurement bandwidth

– Frequency extension module– Coaxial cable– Waveguide

• Multiple measurements required– Reconnecting sensitive equipment– Warmup– Calibration

Typical waveguide bands for mmW and sub-mmW measurements

coaxial0-110 GHz

WR6110-170 GHz

WR5140-220 GHz

WR3220-325 GHz

WR2325-500 GHz

DC – 110 GHz

110 – 170 GHz

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Motivation• Limited measurement bandwidth

– Frequency extension module– Coaxial cable– Waveguide

• Multiple measurements required– Reconnecting sensitive equipment– Warmup– Calibration

Typical waveguide bands for mmW and sub-mmW measurements

coaxial0-110 GHz

WR6110-170 GHz

WR5140-220 GHz

WR3220-325 GHz

WR2325-500 GHz

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• Passive dual band probe• Integrated diplexer

into probe housing– 1.0 mm connector (DC-110 GHz)– WR-06 connector (110-170 GHz)

mmW Head Controller

DUT

DC-170 GHz probe with integrated diplexerWR-06

Extension Module40 MHz - 110 GHz

Extension Module110 - 170 GHz

1 mm coax

WR-06

Extension Module40 MHz - 110 GHz

Extension Module110 - 170 GHz

1 mm coax

Dual Band On-Wafer Probe• Combining adjacent

frequency bands within one single measurement

• using existing measurement hardware

• 4-port NWA for 2-port measurement

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Outline

Why including Diplexers in RF Probe

Motivation

Diplexer TheoryWorkflow

Filter Design

Scale Down Prototype

Measurement Example

Verification

Conclusion Outlook

Roundup

7

Modified Tables for Optimum DiplexersDesign Goals:

• Low Loss• Return Loss < -10 dB• Isolation 20 dB

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Modified Tables for Optimum DiplexersDesign Goals:

• Low Loss• Return Loss < -10 dB• Isolation 20 dB

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Suspended Stripline (SSL)• Good shielding

– Embedded in split-block

• Most of the field components in air

– Low loss– Low dispersion

• Single mode (f < 200 GHz)• Wide impedance range

low impedancehigh impedance

MS GCPW SSL

Zmin 8 Ω 10 Ω 8 Ω

Zmax 132 Ω 147 Ω 183 Ω

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SSL Transitions

WR06 waveguide• Return Loss < -15 dB• 110 – 170 GHz

1.0 mm coax• Return Loss < -25 dB• DC – 110 GHz

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SSL Transition – Probe Pad• SSL GCPW Infinity Probe• Return Loss < -25 dB

top bottom split-block

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400 µm

300 µm via fence

Layerstack – FormFactor Membrane• Via fence

– Suppress substrate modes– Electrical connection of split-block parts

12 µm sub 2

20 µm sub 1

15 µm sub 0

6 µm met 2

5 µm met 1

• Milled wedge– Cuts part of the membrane– Replacement of via in sub 0

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Low Pass Filter DesignStepped impedance filter

• Series inductance high impedance line• Parallel capacitor low impedance line• Quasi-lumped approach: l = λ/8

– neglect parasitic effects

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Band Pass Filter DesignCoupled resonator filter

• λ/2 transmission line• Capacitive coupling

Equivalent circuit based on 3D EM simulations• Objective: Find link between CST parameers and ADS components

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Diplexer with BPF – DC-110-170 GHz Diplexer design

• Stepped impedance LPF• Coupled Resonator BPF

T-Junction: individual parameter adjustment

• Phase relation LPF – BPF• Cin BPF• Line1 length LPF

Cin

ϕLPF-BPF

line1

3D EM Simulations

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High Pass FilterQuasi-lumped elements filter

• Series capacities– End-coupled line sections

on opposite sides of the PCB– C1 = 6 fF– C2 = 5 fF– Cpar = 0.3 fF

• Parallel inductances– Short-circuited

high impedance stub– L1 = 140 pH

• finite length of T-junction– Requires transmission-lines

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Diplexer DC-110-170 GHzDiplexer design

• Stepped impedance LPF• Quasi concentrated HPF

T-Junction:• Phase relation LPF – HPF• Cin HPF• Transmission line at HPF input

– Decouple T-junction & HPF• Line1 length LPF

3D EM simulation:• Well matched < -20 dB• Low insertion loss• Sharp separation of frequency bands

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Outline

Why including Diplexers in RF Probe

Motivation

Diplexer TheoryWorkflow

Filter Design

Scale Down Prototype

Measurement Example

Verification

Conclusion Outlook

Roundup

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Scaled down by ×10• DC-11-17 GHz• Rogers RO4003C

– 508 µm thickness

• SMA connectors• Easy to manufacture• Easy to measure

Scaled Down Prototype: DC-11-17 GHz

500

µm

low impedance

4 mm

3 m

m

high impedance

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Outline

Why including Diplexers in RF Probe

Motivation

Diplexer TheoryWorkflow

Filter Design

Scale Down Prototype

Measurement Example

Verification

Conclusion Outlook

Roundup

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ConclusionOn-wafer probe with integrated diplexer

• Combining adjacent frequency bands within one single measurement

• Using measurement equipment

Diplexer design method• Modified tables & Equivalent circuits• Optimization with >25 parameters

Outlook• Realization and characterization

of dipelxers DC-110-170 GHz• Integration into on-wafer probe housing

mmW Head Controller

DUT

DC-170 GHz probe with integrated diplexerWR-06

Extension Module40 MHz - 110 GHz

Extension Module110 - 170 GHz

1 mm coax

WR-06

Extension Module40 MHz - 110 GHz

Extension Module110 - 170 GHz

1 mm coax

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Thank You!

For questions, please contact:Florian Boes

Karlsruhe Institute of TechnologyInstitute of Radio Frequency Engineering

and Electronics

florian.boes@kit.edu