RFID SysTech’07

Design Methodology of a Voltage Multiplier for Full

Passive Long Range UHF RFIDAlexander Vaz, Aritz Ubarretxena, Daniel Pardo,

Iñaki Sancho, Roc Berenguer

Outline1. Introduction2. System constraints3. Voltage Multiplier Design

A. Improving the efficiencyB. Performing the input impedanceC. Output VoltageD. Steps to follow

4. Examples5. Conclusions

RFID SysTech’07

1. Introduction

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1. IntroductionBlocks Diagram

RFID SysTech’07

2. System Constraints

2. System Constraints3 limitations for the communication range:

• Reader Tag–Minimum input power–Minimum input voltage

• Tag Reader–Probability of error

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2. System ConstraintsMinimum input power

( ) [1] 14

422

2

DIGANAA

AV PPXR

XP +≥+ η ( )( )DIGANAA

eirpP PPXR

GXPr

++≤ 222

22

44πηλ

Incident power > Tag Power consumption

PRFin

[1] G. De Vita and G. Iannaccone, “Design Criteria for the RF section of UHF and Microwave passive RFID transponders”IEEE Trans. Microw. Theroy Tech., vol. 53, no.9, pp. 2985-2989, Sep. 2005

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2. System ConstraintsMinimum input voltage

• Matching Network is required– Maximum power transference increase efficiency

– Increment of the voltage (V2 > V1)

min47.0

VGRPQ

r AeirpmnV π

λ≤

mnxQVV

7.01

2 ≅

AAV RPV =1

[2]

[2] D. Pardo, A. Vaz, A. García-Alonso, R. Berenguer. “Design criteria for full passive long range UHF RFID sensor for human body temperature monitoring”. IEEE RFID 2007. Mar. 2007.

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2. System ConstraintsProbability of error

• To achieve appropriate communication Pe < 10-3

BPSK constellation

( ) ( )( ) ( )[1] 10

2sin

21cos2sin

21 3−≤

⎭⎬⎫

⎩⎨⎧

⎟⎠⎞

⎜⎝⎛

⎟⎠⎞

⎜⎝⎛ −

=σθ

σϕθ AerfAerfPe

[1] G. De Vita and G. Iannaccone, “Design Criteria for the RF section of UHF and Microwave passive RFID transponders”IEEE Trans. Microw. Theroy Tech., vol. 53, no.9, pp. 2985-2989, Sep. 2005

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RFID SysTech’07

3. Voltage Multiplier Design

Variable Guide

Vfwr ↓ Schottky diodesZero threshold transistors

VIN ↑ Matching network with ↑ QMN

N ~ Depends on the fixed VOUT (the technology used)

KN ↑ Depends on diode area, N, CS and CP

3. Voltage Multiplier DesignDickson’s Topology

VOUT = KNN (VIN-Vfwr)

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3. Voltage Multiplier DesignDetect which one, rp or rv, is more restrictive

A. If rp < rv ↑ Efficiency (η)

( )( )DIGANAA

eirpP PPXR

GXPr

++≤ 222

22

44πηλ

min47.0

VGRPQ

r AeirpmnV π

λ=

B. If rp > rv ↑ Qmn↓ Vmin

Perform ZIN

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3. Voltage Multiplier DesignA. Improving the efficiency (rp < rv)

1) Optimum Diode Area

For 868MHzOptimum Area: 8-10pm2

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3. Voltage Multiplier DesignA. Improving the efficiency (rp < rv)

2) Variation of the number of stages, CS and CP values

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3. Voltage Multiplier DesignB. Performing the input impedance (rp> rv)

( )APAV RRPV −≅ 7.02

( )12 += QRR ICP

IC

IC

RXQ =

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3. Voltage Multiplier DesignB. Performing the input impedance (rp> rv)

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3. Voltage Multiplier DesignC. Output Voltage (VOUT)

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3. Voltage Multiplier DesignSummary

η Q RIC VOUT↑N ↓↓ ↓ ↓ ↑↑↑CS ↑ ↑↑ ↓↓ CSopt

↑CP ~↑ ~↓ ~↑ ~↑

Minimum Number of StagesHigh CS

High CP (not decisive)

↑ηMinimum Number of Stages

High CSLow CP (not decisive)

Optimum ZIN

CS and CP > 400fFHigh N

Optimum CSHigh CP (not decisive)

↑ VOUT

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3. Voltage Multiplier DesignD. Guidelines

1. Determine the optimum diode size2. Select VOUT N Vmin

3. Detect which one, rv or rp, is more restrictive4. Determine CS or CP according to point 35. Calculate the input impedance6. Calculate the matching network

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RFID SysTech’07

4. Examples

4. ExamplesDifferent VM have been fabricated

•Number of stages: 4, 6 and 8

•High Q

•High Efficiency

•Optimized for the chip

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Supply Capacitor

ASKVMLM POR

Reg 1.8 Reg1.2

4. Examples

RFID SysTech’07

5. Conclusions

5. ConclusionsIn order to obtain higher reading distances of the tag VM is criticalA design for the VM has been presented:– Know the real limitation of the RFID system

• Higher Q• Higher Efficiency• Trade off between both

– Design the VM following the guidelines

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RFID SysTech’07

Design Methodology of a Voltage Multiplier for Full

Passive Long Range UHF RFIDAlexander Vaz, Aritz Ubarretxena, Daniel Pardo,

Iñaki Sancho, Roc Berenguer