HF-RFID. References. School of Engineering

Transcription

1 HF-RFID MSE, HF-RFID, 1 References [1] Klaus Finkenzeller, RFID-Handbuch, 5. Auflage, Hanser, [2] R. Küng, M. Rupf, RFID-Blockkurs, ergänzende MSE-Veranstaltung, ZHAW, Kontakt: ZHAW Zürcher Hochschule für angewandte Wissenschaften Prof. Dr. M. Rupf ZSN Zentrum für Signalverarbeitung und Nachrichtentechnik Technikumstrasse 9, TB 425 CH-8401 Winterthur Tel: ++41 (0) Mail: marcel.rupf@zhaw.ch Web:

2 Inductive RFID-Reader from [2] MSE, HF-RFID, 2 TX DATA Reader => Tag ASK-Modulation PA C1 CONTROL UNIT CARRIER ENABLE RX DATA LNA R1 L1 INDUCTIVE ANTENNA serial resonance (current!) f r 2 1 L C 1 1

3 Inductive Passive Tag from [2] MSE, HF-RFID, 3 Reader sends unmodulated carrier --> serves as tag supply and local oscillator RX Data Vcc C INDUCTIVE ANTENNA parallel resonance (voltage!) L2 C2 Rmod (Cmod) TX Data GND CONTROL UNIT f r 2 1 L 2 C 2 Cc CLK generator System Clock

4 Voltage at tag chip How the Tag Voltage is built partly from [2] MSE, HF-RFID, 4 useful for frequencies up to 100 MHz Parallel Resonance Circuit Load L2 C2 Resonance peak easily detunable (e.g. tag near conducting surfaces) Coil only Frequency [MHz] MHz HF-Tag with a coil with a few turns only (2π f turns res ) LC 1 L ~1/f res, L ~ N Nturns ~ 1/f res LF-tag coils: turns => HF-tag coils: 3-10 turns (cheaper!)

5 Reading Range from [2] MSE, HF-RFID, 5 k ~ r r 2 R R r r T 2 T cos( ) 2 2 r x 3/ 2 R Design Rule: Make small, antenna r 2 big field strength (~k) decreases with 1/x 3-60 db / decade Available RF power (~k 2 ) rapidly falls off with distance even when in a range corresponding to antenna diameter rule of thumb: reading range of credit card tags diameter of reader antenna

6 Best Orientation MSE, HF-RFID, 6 Inlays receive power by magnetic coupling with the antenna and will receive maximum power when in their best orientation. Source: TI Source: TI Source: TI

7 Reader => Tag: ASK-Modulation from [2] MSE, HF-RFID, 7 ASK modulation depth %

8 Tag => Reader: Load Modulation partly from [1] MSE, HF-RFID, 8 y(t) Source [1] uplink FET-switch closed y(t) e.g. data 0 envelope carrier f c (not shown) Rx-signal = AM with carrier! T b t e.g. data 0 (Manchester coded) e.g. R b = 1/T b = f c / 512 e.g. f subcarrier = f c / 32 T b t

9 Tag => Reader: Load Modulation MSE, HF-RFID, 9 Tag-response in baseband T b t 0 f Tag-response subcarrier-modulated T b t -f sub 0 f sub f reader envelope t T b f c -f sub f c f c +f sub f

10 Tag => Reader: Load Modulation MSE, HF-RFID, 10 Spectrum of the Rx-signal IY(f)I huge dynamic range (e.g. 80 db) filtering sideband (with info) f f c -f subcarrier f c f c +f subcarrier Q-factor of inductive reader- and tag-antenna compromise between long range (high voltage peak) and good carrier-subcarrier separation (facilitates demodulation) IY(f)I antenna BP-characteristic - 3 db (Q = f c / B 3dB < 20 Q too large rec. for ISO 15693) f c khz f c MHz f c khz f

11 HF-Band-Regulations World-Wide from [2] MSE, HF-RFID, 11 Frequency bands in MHz use: 42 dbua/m at 10 m Only 1 single channel Tight transmit spectral mask Far field limit at 10 m Most important band today is UHF Source: ERC/REC Annex 9

12 Some LF- and HF-RFID-Standards MSE, HF-RFID, 12 Goal readers and tags from different suppliers are interoperable typically Tx-procedure is standardized, but not the Rx => contention! LF ISO/IEC 11784/5 and extension identification of animals HF ISO/IEC Identification Cards Proximity Cards (2001) range up to 10 cm, data rate 106 kb/s, more details later ISO/IEC Identification Cards Vicinity Cards (2001) range up to 1 m, data rates up to 26 kb/s also ISO/IEC mode 1 ISO/IEC mode 3 (item management standard) HF-version of EPC UHF Gen2, high data and tag reading rates more details later

13 Near Field Communication (NFC) MSE, HF-RFID, 13 NFC-Interface and Protocol Standards NFCIP-2 (ECMA-352 / ISO-21481) NFCIP-1 (ECMA-340 / ISO-18092) NFC-Controller mit NFCIP-2 NFC-device e.g. with OS passive communication mode ISO VCD mode reader/writer 26 kbps ISO A/B PCD mode reader/writer 106 kbps RF-detection, set-up-time < 0.1s PICC mode card-emulation 106 kbps active comm. mode NFC-mode peer-to-peer 106 / 212 / 424 kbps (> 424 kbps in R&D) MHz inductive (few cm) VICC PICC PCD NFC-device memory card memory card processor card

14 HF-RFID-Standard ISO MSE, HF-RFID, 14 Norm for contactless chip-cards basis for many other smart-label-products MHz, range < 1 m (vicinity coupling) Standard from 2001 with 3 parts ISO :2000: Physical Characteristics CHF ISO :2006: Air Interface and Initialization CHF ISO :2009: Anticollision and transmission protocol CHF Terms and definitions VCD: vicinity coupling device ( reader ) VICC: vicinity card ( tag )

15 VCD-to-VICC Communication ASK-Modulation MSE, HF-RFID, 15 ASK-modulation with 10% and 100% modulation depth The VICC shall decode both. The VCD determines which index is used.

16 VCD-to-VICC Communication Pulse Position Modulation MSE, HF-RFID, 16 1 out of 256 data coding (long distance mode) 1.65 kb/s 1 out of 4 data coding (fast mode) SOF (start of frame) EOF (end of frame) kb/s μs

17 VICC-to-VCD Communication MSE, HF-RFID, 17 Operating field A VICC shall operate between H min (150 ma/m) and H max (5 A/m rms). Load modulation inductive coupling Data rates and subcarrier one subcarrier: f s1 = f c /32 ( khz) two subcarrier: f s1 = f c /32 ( khz) and f s2 = f c /28 ( khz) (FSK)

18 VICC-to-VCD Communication MSE, HF-RFID, 18 Bit-coding when using one subcarrier (high bit rate) Logic 1 (Manchester coding) SOF (start of frame) EOF (end of frame) Bit-coding when using two subcarrier (high bit rate) SOF (start of frame) EOF (end of frame) Logic 0 (Manchester coding)

19 Anticollision and Transmission Protocol MSE, HF-RFID, 19 VICCs are uniquely identified by a 64 bit unique identifier (UID) Application family identifier (AFI) used to extract only the VICCs meeting the required application criteria (e.g. transport etc.), AFI-support by the VICCs is optional VICC memory organization => can be locked (permanently) or not locked Please note that Tags just support 32 bit memory blocks today. Therefore, some Tags have a memory with 2048 x 32 bit blocks. But then, a special flag must be used which is not supported by all Reader (versions).

20 Anticollision and Transmission Protocol MSE, HF-RFID, 20 Overall protocol description VCD talks first VCD Request VICC Response time General request format General response format

21 Anticollision and Transmission Protocol MSE, HF-RFID, 21 Inventory request inventory

22 Anticollision and Transmission Protocol MSE, HF-RFID, 22 Inventory request see ISO :1999, chapter 8.3 EOF/SOF UID success idle VICC responds if Slot-number = 4 LSBs of the UID if the mask is empty

23 ISO Anticollision: Example MSE, HF-RFID, 23 Assume there are 4 Tags in the Reader field with UIDs 81 (hex: 51) 85 (hex: 55) 165 (hex: A5) 170 (hex: AA) - C C

24 Command Codes (Requests) MSE, HF-RFID, 24 VICC exits when power off, reset to ready, locks permanently the requested block enters the selected state exits the quiet state (over) writes the application family ID locks the AFI permanently (over) writes data storage format identifier sends system information

25 Read Single Block MSE, HF-RFID, 25 VCD unadressed VICC typ. 32 bits time Fastest access to moving tags (e.g. on conveyor belt / production line) Tag "identification" with (32 bit) memory-block and not with the UID no anticollision procedure, at most 1 Tag in the (small) Reader field Minimum exposure time in the Reader field 8 ms (cf. Exercise 1, problem 8) => up to 125 moving Tags per s readable