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12/8/14

Group Members: Ryan Gough, Ashikur Rahman, Julian Cheng

Member Emeritus: Ehsan Yavari

SWITCHCRAFTProject 1 Final Presentation

Group 2

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Project ObjectiveDesign and build two solid state RF switches

One switch with PIN diode(s), and one with FET(s)

Primary Design Parameters

• Operational at 4 GHz• Minimize insertion loss• Maximize isolation

Secondary Design Parameters

• Minimize DC power consumption• Simplicity• Bandwidth

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The GameplanParts Selection

VICTORY!

AcceptablePerformance?

AcceptablePerformance?

Modular Fab(PIN)

Modular Fab(FET)

Full Fab(PIN)

Full Fab(FET)

AcceptablePerformance?

AcceptablePerformance?

Initial Design

Rework/Redesign

Rework/Redesign

Rework/Redesign

Rework/Redesign y y

y y

nn

nn

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Parts SelectionChose PIN diode and FET based on low-cost, immediate availability,

advantageous operating parameters, and ease of modeling.

Manf. P/N Max Fwd.Current

Max ‘On’ Resis.

Max Total Cap. Inductance S2P?

Skyworks SMP1345-079LF 100 mA 2 Ω 0.20 pF 0.7 nH Yes

Manf. P/N Packaging Max. Drain Current Pinch-off S2P? ADP model?

Avago ATF-38143 SOT-343 145 mA -0.5V Yes Yes

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PIN Diode Switch

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Initial Design – Diode SwitchThree shunt diodes with matching network

DIODE #1 DIODE #2 DIODE #3

DIODES OFF / SWITCH ON: Low-value capacitor presents high impedance to primary line

DIODES ON / SWITCH OFF: Primary line exposed to quarter-wave transformer stub; creates three short circuit nodes 90° apart

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Initial Design – Diode Switch

Device parasitics already included in S2P

Stub is performing tuning; extra cap not needed

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Diode Switch - Modular FabricationIteration #1: Tuning stub worked, but inductor position at the

lower end limited available tuning range.

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Diode Switch - Modular Results

Single-stage shunt diode with open-circuit tuning stub

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Diode SwitchStubs create RF short circuit at three points (90° apart) to

discourage anti-nodes

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Diode Switch ResultsIsolation: 57.6 dB (@ 4.07 GHz)Better than 20 dB: 3.54 – 4.47 GHz (23.3%)

VDC = 1.8 VDC IDC = 300 mA

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Diode Switch ResultsInsertion Loss: 1.3 dB3dB Bandwidth: 1.84 GHz (46%)

VDC = -2 VDC IDC = 0 mA

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FET Switch

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Initial Design – FET SwitchTwo FETs in series; gate-controlled

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Initial Design – FET SwitchInsertion Loss: 0.3 dBIsolation: 19.4 dB

This switch stuff is easy!!!!

+3VDC Vgs -3VDC Vgs

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FET Switch Trouble

Series FET deviates significantly from ADS simulation

Measured data courtesy Group 3

~7.2 dB disparity in isolation

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FET Switch Updated DesignSimplified design and switched (!) to shunt topology

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Insertion Loss: 2.3 dBIsolation: 40.2 dB

FET Simulated Results

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FET Switch

FET

Tuningstub

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FET Switch ResultsIsolation: 22.3 dB (@ 4.0 GHz)Better than 20 dB: 3.63 – 4.15 GHz (13%)

VDC = -0.9 VDC IDC = < 1 mA

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FET Switch ResultsInsertion Loss: 6.2 dB (@ 4.0 GHz)

VDC = 0 VDC IDC = 0 mA

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FET Switch ResultsBest case insertion loss: 3.1 dB (@ 4.0 GHz)

At this stub length, isolation is only 7.0 dB

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FET Switch ResultsIsolation improves as a function of stub length on either side of 4 GHz. : (

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Summary

Successfully fabricated RF switches with both PIN diodes and FETs.

PIN Diode Switch• Num. Devices: 3• DC Power: 540 mW (1.8 VDC @ 300 mA)• Insertion Loss: 1.3 dB• Isolation: 57.6 dB

FET Switch• Num. Devices: 1• DC Power: < 1 mW (0.9 VDC @ < 1 mA)• Insertion Loss: 6.2 dB (3.1 dB best case)• Isolation: 22.3 dB

Supplemental

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Parts Selection – PIN DiodesNeed a low-cost, readily available option that operates @ 4 GHz

Manf. P/N Packaging In Stock? Cost (per unit) Dist. Upper

Freq.

Infineon BAR 64-03W E6327 SOD 323 Yes $0.50($0.297 @ 10) Mouser “SHF”

Infineon BAR 64-02V H6327 SC 79 Yes $0.51($0.359 @ 10) Digikey 6 GHz

MACOM MADP-0110280-1415OT SMD Yes $3.05($2.47 @ 10) Mouser 12 GHz

MCC BAP51-02-TP SOD-523 Yes $0.52($0.371 @ 10) Digikey N/A

Skyworks SMP1345-079LF SC 79 Yes $0.55

($0.503 @ 10) Mouser 6 GHz

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Parts Selection – PIN DiodesPerformance specs? Ease of simulation?

Manf. P/N Max Fwd.Current

Max ‘On’ Resis.

Max Total Cap.

Inductance S2P?

Infineon BAR 64-02V H6327 100 mA 1.35 Ω 0.17 pF 0.6 nH No

Skyworks SMP1345-079LF 100 mA 2 Ω 0.20 pF 0.7 nH Yes

Infineon has slightly better specs at a slightly lower price, but without an S2P file it will be more difficult to model.

Final decision was to select the Skyworks SMP1345.

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MESFETs expensive… expanded search to include other FETs.

Manf. P/N Packaging In Stock? Cost (per unit)

UpperFreq. FET Type

MWT MWT-773 Pkg 73 Yes $27.40 26 GHz MESFET

Avago ATF-58143 SOT-343 Yes $2.87 6 GHZ pHEMT

CEL NE3510M04-A M04 Yes $1.75 12 GHZ HJFET

Avago ATF-33143 SOT-343 Yes $4.10($3.65 @ 10) 10 GHZ pHEMT

Avago ATF-38143 SOT-343 Yes $1.31 10 GHZ pHEMT

Parts Selection – FETs

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Other parameters?

Manf. P/N PackagingMax. Drain

CurrentPinch-off S2P? ADP

model?

CEL NE3510M04-A M04 97 mA -0.7V No No

Avago ATF-38143 SOT-343 145 mA -0.5V Yes Yes

The Avago FET is less expensive, and comes with both S2P files and an ADP model.

Parts Selection – FETs

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Device OperationPIN Diode

• Wide intrinsic region acts as low-value capacitor under reverse bias

• Variable RF resistor under forward bias

Field Effect Transistor

• Gate voltage below pinch-off prevents current through channel; drain-source capacitance remains

• Gate voltage above pinch-off allows conduction; variable resistor to RF

Images from Agilent white paper: “Understanding RF/Microwave Solid State Switches and their Applications”

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Diode Switch - Modular Fabrication

Iteration #2: Moved inductor to top of stub… success!

(Re-purposed SMAs before remembering to take a photo. Whoops.)

SC-79

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Initial Design – FET SwitchOpen circuit stub for matching

M04

SOT-343