UHF-Technology. Vorlesung RFID Systems Benno Flecker, Michael Gebhart TU Graz, Sommersemester 2016

Transcription

1 UHF-Technology Vorlesung RFID Systems Benno Flecker, Michael Gebhart TU Graz, Sommersemester 2016

2 RFID System A traditional passive label (tag) is queried and it responds with it s ID accordingly. Power and commands are transferred with different frequencies (UHF [ MHz], HF [13.56MHz], LF [125 & 134.2kHz]. Power & Commands Serial Number / Data Seite 2

3 Interactive RFID I 2 C devices I 2 C serial interface to traditional RFID Enables bidirectional communications between electronics and the traditional RF interface RFID tag would typically be incorporated in the electronic PCB RFID I 2 C Electronic Device Bidirectional Communications Seite 3

4 RFID Technology Elements One Time Programmable (OTP) Read Only (RO) Read / Write (R/W) Memory Slotted Aloha Binary Tree Anti-collision Handling Power Supply Passive Semi-passive Active Sensors Localization Cryptography Special Features RFID System ID Format UID EPC 96bit 125 /134.2 khz MHz MHz 2.45 GHz (5.6 GHz) Operating Frequency Transponder Type Tag (rigid) Label (flexible) Protocol Reader Talks First (RTF) Tag Talks First (TTF) Seite 4

5 Used RFID technology and its properties Low frequency (125kHz) Read Range ~ 1m one tag each time Works well in harsh environment Transponder cost System cost High frequency (13.56MHz) Read Range ~ 1.5m 40 tags at the same time Works well in harsh environment Transponder cost System cost Ultra high frequency ( MHz) Very long read ranges of up to 10+m 1000 tags/sec Susceptible to harsh environment Transponder cost System cost Seite 5

6 LF Technology Standards: ISO 11784/85 Animal ID, TTF ISO RTF & TTF ISO Item Management National Regulations: Worldwide harmonized Physical concept: Inductive coupling Operating frequency: 125/134.2 khz Antenna: Coil Operating distance: Up to 1m Environmental influences: Weak influence on operating distance Works in metal environment Application: Animal identification Industrial environment Access Control Seite 6

7 HF Technology Standards: ISO Vicinity Card ISO Proximity Card ISO Item Management HF EPC Gen2 National Regulations: Worldwide harmonized Physical concept: Inductive coupling Operating frequency: MHz Antenna: Coil Operating distance: Vicinity: up to 1.5m Proximity: up to 10cm Environmental influences: Weak influence on operating distance Works in metal environment Application: Libraries Public transport Product identification Access control, Seite 7

8 UHF Technology Standards EPC Class I Gen2 ISO Item Management National Regulations: No worldwide harmonized Physical concept: EM wave propagation Operating frequency: MHz Antenna: Dipole and/or loop Operating distance: Far field: up to 7m Near field: up to 10cm Environmental influences: Influence on operating distance by reflection and absorption Application: Pallets and container ID Fashion Retail Electronics Seite 8

9 Information from EPCglobal HP (Free Download) Class 1 Generation 2 UHF Air Interface Protocol Standard "Gen 2" EPC Tag Data Standard (TDS) EPC Tag Data Translation (TDT) Standard Mask Designer ID Assignment (MDID) Frequency Regulations UHF Seite 9

10 Frequency allocation by countries Frequency Regulations UHF Seite 10

11 P EIRP - Equivalent Isotropic Radiated Power vs. P ERP - Effective Radiated Power P ERP... transmitted power compared to a dipole antenna ERP: Effective radiated power. The amount of power that would be necessary at the input terminals of a reference half-wave dipole antenna in order to produce the same maximum field intensity. P EIRP... transmitted power compared to an isotropic antenna EIRP:Equivalent isotropically radiated power (EIRP). The amount of power that a theoretical isotropic antenna would need to emit to produce the peak power density observed in the direction of maximum antenna gain is equivalent to 2.15dB Gain and Directivity ERP PEIRP 1.64 if the antenna has no electrical losses, then G = D P G P P transmitted conducted D Seite 11

12 Maximum Radiated by countries (P EIRP ) Seite 12

13 Energy Transmission from Reader to TAG Transferred power from a reader antenna to the chip P Chip P EIRP 2 (4 R) Matching 2 Matching... Antenna matching factor( 1 ) Polarisation... Polarisation losses Antenna... efficiency of the label antenna (P radiated / P in ) 2 Polarisation Antenna G Label Seite 13

14 Read Range of an UHF/GHz Chip R max P G 2 EIRP Label 2 (4 ) PChip Matching Polarisation Antenna Example I (UHF) under US regulations: P EIRP = 4 W; G Label = 1.64; f = 915MHz; P CHIP = 35µW Matching = 0.8; Polarisation = 1; Antenna = W m R max m 2 6 (4 ) W Seite 14

15 Read Range of an UHF/GHz Chip Example II (UHF) under EN European regulation: P ERP = 2 W equals P EIRP = 3.28W; G Label =1.64 f = 869MHz; P CHIP = 35µW Matching = 0.8 ; Polarisation = 1 ; Antenna = W m R max m 2 6 (4 ) W Seite 15

16 UHF Memory structure Reserved Memory EPC Memory TID User Memory Access and Kill Password EPC Electronic Product Code Code can be written by user TID Tag Identifier (preprogrammed & locked) IC Manufacturer information, Unique serial number Manufacturing, quality and product related data storage User related data storage Seite 16

17 Anti collision algorithm Seite 17

18 Communication with the tag Inventory (1 Communication step) Command (e.g. READ TID) Seite 18

19 Tag Inventory flag Seite 19

20 Tag persistence Seite 20

21 Effect on search mode and sessions Tag in the field Tag out of the field Dual Target A B A B A B A B A B A B A B A B A Reader A&B R R R R R R R R R R R R R R R R R Singel Target Session 1 PT S1 PT S1 PT S1 PT S1 A B A B A B A B A R R R R R Reader only A Singel Target Session 2 or 3 A R B PT S2 or S3 Reader only A R: READ PT S1: Persistance Time Session 1 PT S2 or S3: Persistance Time Session 2/ 3 Seite 21

22 Environmental Influence - Overview UHF-Characteristics Absorption/Damping Reflection Refraction Diffraction Penetration into Liquids Interference Polarisation Seite 22

23 Environmental Influence - Overview Absorption/damping Only vacuum is passed by electromagnetic energy without absorption Absorbed energy is typically converted to heat Absorbing materials between the reader antenna and the label antenna strongly determines the operating range of the label Absorbing materials Water, water absorbing materials Rubber, adhesives, Seite 23

24 Environmental Influence - Overview Reflections A pure reflection of the travelling wave, will conserve the energy of the field Will lead to interferences Constructive interference may lead to super ranges Destructive interferences may lead to holes in the operational area Reduce this no-read situations with multiple antennas Reflecting materials Metal, water, concrete Metallic paints - films - foils Seite 24

25 Environmental Influence - Overview Refraction caused by the velocity difference of the EM wave between one propagation medium and a second lead to a change of the wave direction medium border ε r ε r1 Seite 25

26 Environmental Influence - Overview Diffraction occurs by passing a sharp corner Huygens principle is based on this process Representation of Radio Waves as Wavelets Seite 26

27 Environmental Influence - Overview Penetration into Liquids Depending on the electrical conductivity of the liquid Water has a high electrical conductivity and will tend to absorb and reflect EM waves Oil derivates allows an EM wave to pass with a low level of attenuation, if no additives are used. Seite 27

28 Environmental Influence - Reflections Application Effects Expanding operation range guiding travelling waves with the help of e.g. metal (Truck,...) Shielding wanted separation from places of identification hiding items from being identified (wrapping into conducting foil) unwanted e.g. labels inside a pallet of tin cans may not be recognized Seite 28

29 Environmental Influence - Interferences Example Propagation of travelling waves in free space Z Y ideal dipole X Different field-strength Idealized linear polarized dipole Polarisation: y - axis Picture: xz - plane Seite 29

30 Environmental Influence - Interferences Example Propagation of travelling waves in free space Z Y ideal dipole X Idealized linear polarized dipole Polarisation: y - axis Picture: xy - plane Seite 30

31 Environmental Influence - Interferences Example Propagation of travelling waves with reflecting floor field-holes Y Z X Idealized linear polarized dipole Polarisation: z - axis Picture left: zy - plane / Picture right: xy - plane Seite 31

32 Environmental Influence - Interferences Example Propagation of travelling waves with reflecting floor super-range Y Z X Idealized linear polarized dipole Polarisation: y - axis Picture left: xz - plane / Picture right: xy - plane field-hole Seite 32

33 Environmental Influence - Interferences Example Propagation of travelling waves with reflecting wall Z Y X...wall Idealized linear polarized dipole Polarisation: y - axis Picture: xz - plane Seite 33

34 Environmental Influence - Interferences Application Effects Close to reflecting planes, interferences will lead to standing waves Moving labels may cross spots of field nulls and may loose it s internal states Z Y Idealized linear polarized dipole Polarisation: y - axis Picture: xz - plane X...wall Seite 34

35 Multi Antenna Arrangements A single reader antenna will in many cases not be sufficient for desired applications Preferred way to use more than one reader antenna is multiplexing, controlled by the reader The reader starts its task (e.g. identify all tags in the field) at the first antenna. After finishing this job the next antenna can be used... Seite 35

36 Multi Antenna Arrangements Positioning A given operational space has to be covered by the sum of the operational spaces of all individual antennas The more overlap the antenna arrangement has, the more reliable the identification will be For applications with many, fast moving items the antenna switching may be improved by external detectors e.g light barrier Operational spaces may be a affected by the items that have to be identified (shielding, absorbing) Seite 36

37 Multi Antenna Arrangements Positioning Parallel mounted Gate antennas Seite 37

38 Content Antenna Design Antenna design Inputs Antenna design Parameter Direct chip assembly Pmin measurement Identify the right tag Label / Tag provider RFID PCB antenna designer Seite 38

39 Antenna design inputs IC Dimensions, coating Size Label Size, Antenna Size Antenna Substrate Material; Thickness Antenna Conductive materials Material; Thickness; Line width; Gap width; min. corner radius Performance Required Frequency Bands; US; EU Application Free Air; Cardboard; Plastic; Other material Stacked tags Max. no. of tags; Min. distance of tags Chip Attachment - Direct Attach: Expected Assembly Capacitance Seite 39

40 Assembling Parasitic Capacitances C parasit C chip R C tot C parasit C chip Seite 40

41 Reference antenna design FF9510 Seite 41

42 Range [m] FF9510 Change loop size Loop Size Increase Delta Loop = 0 mm Delta Loop = 0.57 mm Delta Loop = 1.05 mm Delta Loop = 1.52 mm Delta Loop = 2.00 mm FREQ [GHz] Seite 42

43 Rang [m] FF9510 Change dipole length 7 6 dl dipole = 0 mm dl dipole = mm dl dipole = mm dl dipole = mm dl dipole = mm L decrease Freq [GHz] Seite 43

44 Range [m] FF9510 Change connection dipole loop Distance Reduction Distance Reduction Delta Dipole = 0 mm Delta Dipole = mm Delta Dipole = mm Delta Dipole = mm Delta Dipole = mm Delta Dipole = mm FREQ [GHz] Seite 44

45 FF9510 Total Gain 868 MHz Seite 45

46 Direct Chip attach 150µm, 120µm with 18µm gold bumps Pressure Temperature Pressure Temperature ACP/ACF Anisotropic Conductive Paste/Foil (Adhesive with conducting particles 10k - 40k particles per mm 2 ) Substrate Material: Paper, PET, PC; Thickness 38µm or 50µm Antenna Structure Material: Al, Cu, Ink Etched, Printed, Laser cutted Seite 46

47 Antenna gap A Maximum antenna gap (average distance + tolerance) IC placement accuracy MB +/-50µm Remark: Add etching tolerances - Check with the antenna supplier! Seite 47

48 Seite 48

49 Assembled die Seite 49

50 Pmin Measurement setup EPC global document Tag Performance Parameters and Test Methods Version Seite 50

51 Pmin - Anechoic chamber Seite 51

52 FF µm Reference materials Measured with Voyantic Tagformance ( Seite 52

53 Identify the right tag Size Application Memory Read / Write Sensitivity Write cycles Data retention Seite 53

54 Label / Tag provider Avery Dennison ( Smartrac ( Confidex ( Seite 54

55 Thank you for your Audience! Please feel free to ask questions... Seite page 55