RFID Reader Frontends for a Dual-Frequency (13 MHz and 868 MHz) Rapid Prototyping Environment Robert Langwieser, Michael Fischer and Prof. Dr. Arpad L. Scholtz Vienna University of Technology www.tuwien.ac.at Institute of Communications and Radio-Frequency Engineering Gußhausstrasse 25/389 Vienna, 1040 Austria www.nt.tuwien.ac.at EEEfCOM 2008, Ulm www.nt.tuwien.ac.at/cdlab
Outline Reader Tag Communication Analog Frontends for Rapid Prototyping Environments HF-Frontend UHF-Frontend 2
Reader Tag Communication RFID Reader Data Energy Passive Tag 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 3
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 4
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 5
HF-Frontend: Carrier Suppression Principle 6
HF-Frontend with Tag-Emulator 7
HF-Frontend: Verification Coil Voltage Output Voltage Laboratory setup with tag-emulator Optimal tuning Modulation signal enhanced by 34 db 8
Measurement with Commercial Tag Transmit coil voltage Carrier-suppressed output voltage of the HF-Frontend Distance between tag and transmit coil d = 24 mm Magnetic field at tag position (without Tag) H = 2.4 A/m 9
UHF-Frontend Requirements Rx/Tx crosstalk Antenna configurations Active Rx/Tx decoupling Frontend concept Verification measurement 10
Requirements Frequency: 865MHz - 868MHz Communication range: up to 10m 2 Watt linear output power Interface with the DSP-hardware frequency: 867MHz not directly possible frequency conversion necessary power level: determined by ADCs and DACs Carrier to sideband ratio improvement (carrier suppression) 11
Separate Rx/Tx Antenna Rx/Tx isolation: 30 to 40 db coupling two antennas Rx/Tx isolation depends on: -antenna spacing -antenna radiation pattern 12
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 13
Active Rx/Tx Decoupling Coupler Tx (+33dBm) S21 S21 I-CTRL Q-CTRL Vector Modulator Amp. coupling 20dB -27dBm Coupler Rx +13dBm S21 14
UHF Reader Frontend 15
UHF Transmitter LO2 In 1006 MHz Tx Ant. 868 MHz Ext. PA In 868 MHz To CCU 868 MHz LO1 In 153 MHz Tx In 13.56 MHz Ext. PA Out 868 MHz To CCU 868 MHz Power Supply, Control Lines 16
Measurement Setup Agilent E4416A power meter -20 db R&S SMU200A Mini-Cir. Trigger IQ Tx IN (13.56MHz) Transmitter LO1, -5 dbm LO2, 0 dbm Tx OUT 866.5 MHz CC OUT ZHL-2-12 d R&S SMY01 HP8642B LO1 153.56 MHz Mini-Cir. 4- Way Splitter Mini-Cir. 4- Way Splitter LO2 ZMSC-4-3 ZB4PD1-2000 1005 MHz 1008MHz Carrier Comp. Raditek RC-860-900M -10 db SMA4242-10 Tuner 3 m Cable tag LeCroy 204Xi Demod. OUT Rx OUT (13.56MHz) LO1, -5 dbm Receiver LO2, 0 dbm CC IN Rx IN 866.5 MHz 17
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 18
Received Tag Answer Screenshot at maximum communication range of ~11m 19
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) 20
Thank you! 21