RFID Reader Frontends for a Dual-Frequency (13 MHz and ...R&S SMU200A IQ tag Tx IN (13.56MHz) R&S SMY01 HP8642B LO1, -5 dBm LO1, -5 dBm LO2, 0 dBm LO2, 0 dBm CC OUT CC IN Tx OUT 866.5

Christian Doppler Laboratory for Design Methodology of Signal Processing Algorithmswww.nt.tuwien.ac.at/cdlab

Vienna University of Technologywww.tuwien.ac.at

Institute of Communications andRadio-Frequency EngineeringGußhausstrasse 25/389Vienna, 1040Austriawww.nt.tuwien.ac.at

Robert Langwieser,Michael Fischer andProf. Dr. Arpad L. Scholtz

EEEfCOM 2008, Ulm

RFID Reader Frontends for a Dual-Frequency (13 MHz and 868 MHz)

Rapid Prototyping Environment

2Christian Doppler Laboratory for

Design Methodology of Signal Processing Algorithms

Outline

• Reader – Tag Communication• Analog Frontends for Rapid

Prototyping Environments• HF-Frontend• UHF-Frontend



Reader – Tag Communication

• Tag is powered by the reader • Energy transfer from reader to tag during the

entire communication• Energy transfer happens at the carrier

frequency of the data signal• Cross talk from transmitter to receiver at the

reader

RFID Reader

Passive Tag

Energy

DataData



Analog Frontends for a Rapid Prototyping Environment

• As much functionality as possible should be realized by the digital baseband

• Frequency conversion, filtering and amplification are the tasks of the RF-frontend



HF-Frontend: Requirements

• Frequency: 13.56MHz• Communication range: a few centimeters • Inductive coupling between reader and tag • Load modulation• HF-power of 1 W• Interface with the DSP-hardware

• frequency: 13.56MHz• power levels: determined by ADCs and DACs

• Carrier to sideband ratio improvement



HF-Frontend:Carrier Suppression Principle



HF-Frontend with Tag-Emulator



HF-Frontend: Verification

• Laboratory setup with tag-emulator• Optimal tuning• Modulation signal enhanced by 34 dB

Coil Voltage

Output Voltage



Measurement with Commercial Tag

Transmit coil voltage

Carrier-suppressed output voltage of the HF-Frontend

Distance between tag and transmit coil d = 24 mmMagnetic field at tag position (without Tag) H = 2.4 A/m



UHF-Frontend

• Requirements• Rx/Tx crosstalk

• Antenna configurations• Active Rx/Tx decoupling

• Frontend concept• Verification measurement



Requirements

• Frequency: 865MHz - 868MHz• Communication range: up to 10m• 2 Watt linear output power• Interface with the DSP-hardware

• frequency: 867MHz not directly possiblefrequency conversion necessary

• power level: determined by ADCs and DACs

• Carrier to sideband ratio improvement (carrier suppression)



Separate Rx/Tx Antenna

Rx/Tx isolation: 30 to 40 dB

two antennas

Rx/Tx isolation depends on: -antenna spacing -antenna radiation pattern

cou

pli

ng



Single Rx/Tx Antenna

Rx/Tx isolation: 20 to 30 dB

single antenna

Rx/Tx isolation depends on:-circulator -return loss of antenna

circulator insertion loss: 0.4 – 1 dB



Active Rx/Tx Decoupling

coupling 2

0dB

+13dBm-27dBm

S21S21

S21

S21

Tx

Rx

(+33dBm)

I-CTRL

Q-CTRL

Coupler

Coupler

Vector Modulator

Amp.



UHF Reader Frontend



UHF Transmitter

Tx In13.56 MHz

LO1 In153 MHz

LO2 In1006 MHz

Ext. PA Out868 MHz

To CCU868 MHz

Power Supply,Control Lines

Tx Ant.868 MHz

Ext. PA In868 MHz

To CCU868 MHz



Measurement Setup

4-W

ay

Splitt

er

Transmitter

4-

Way

Splitt

er

Receiver

LeCroy 204Xi

TunerCarrierComp.

Demod. OUT

Rx OUT (13.56MHz)

R&S SMU200A

IQ

tag

Tx IN (13.56MHz)

R&S SMY01

HP8642B

LO1, -5 dBm

LO1, -5 dBm

LO2, 0 dBm

LO2, 0 dBm

CC OUT

CC IN

Tx OUT866.5 MHz

Rx IN866.5 MHz

LO1

LO2 ZMSC-4-3 ZB4PD1-2000

Mini-Cir. Mini-Cir.

Mini-Cir.

Raditek

RC-860-900M

ZHL-2-12

power meter

Agilent E4416A

Trigger

SMA4242-10

-10 dB

153.56 MHz

1005 MHz – 1008MHz

3 m Cable

d

-20 dB



Scenario: Corridor 5th Floor

Power amplifier: Pout = 33.4 dBm

Losses (cable, coupler..): 2.75 dB

Antenna gain: ~5 dBi (~ 2.85 dBd)

Transmit power: ~ 33 dBm ERP



Received Tag Answer

Screenshot at maximum communication range of ~11m



Summary

• Frontends for Rapid Prototyping

• Current implementations for RFID

• HF-Frontend• Rx/Tx decoupling (34 dB carrier suppression achieved)

• Measurements

• UHF-Frontend• Rx/Tx decoupling (antenna configuration, vector modulator)

• Concept and verification(~11m comunication distance achieved)



Thank you!

OutlineReader – Tag CommunicationAnalog Frontends for a Rapid Prototyping EnvironmentHF-Frontend: RequirementsHF-Frontend:�Carrier Suppression PrincipleHF-Frontend with �Tag-EmulatorHF-Frontend: VerificationMeasurement with Commercial TagUHF-FrontendRequirementsSeparate Rx/Tx AntennaSingle Rx/Tx Antenna Active Rx/Tx DecouplingUHF Reader FrontendMeasurement SetupScenario: Corridor 5th FloorReceived Tag AnswerSummary

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/Description > /Namespace [ (Adobe) (Common) (1.0) ] /OtherNamespaces [ > /FormElements false /GenerateStructure true /IncludeBookmarks false /IncludeHyperlinks false /IncludeInteractive false /IncludeLayers false /IncludeProfiles true /MultimediaHandling /UseObjectSettings /Namespace [ (Adobe) (CreativeSuite) (2.0) ] /PDFXOutputIntentProfileSelector /NA /PreserveEditing true /UntaggedCMYKHandling /LeaveUntagged /UntaggedRGBHandling /LeaveUntagged /UseDocumentBleed false >> ]>> setdistillerparams> setpagedevice

Documents

RFID Reader Frontends for a Dual-Frequency (13 MHz and ...R&S SMU200A IQ tag Tx IN (13.56MHz) R&S SMY01 HP8642B LO1, -5 dBm LO1, -5 dBm LO2, 0 dBm LO2, 0 dBm CC OUT CC IN Tx OUT 866.5