UHF-Technology. Vorlesung RFID Systems Benno Flecker, Michael Gebhart TU Graz, Sommersemester 2014

Transcription

1 UHF-Technology Vorlesung RFID Systems Benno Flecker, Michael Gebhart TU Graz, Sommersemester 2014

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 RFID Systems 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 RFID Systems 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) RFID Systems 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 RFID Systems 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 RFID Systems 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, RFID Systems 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 RFID Systems 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 RFID Systems Seite 9

10 Frequency allocation by countries Frequency Regulations UHF RFID Systems 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 G = P = ERP P P conducted PEIRP 1.64 transmitte d D if the antenna has no electrical losses, then G = D RFID Systems Seite 11

12 Maximum Radiated by countries (P EIRP ) RFID Systems Seite 12

13 Energy Transmission from Reader to TAG Transferred power from a reader antenna to the chip P Chip 2 λ = PEIRP ϑmatching ϑ Polarisati on ϑ 2 (4 π R) 2 ϑ Matching... Antenna matching factor( 1 Γ ) ϑ Polarisation... Polarisation losses ϑ Antenna... efficiency of the label antenna (P radiated / P in ) Antenna G Label RFID Systems Seite 13

14 Read Range of an UHF/GHz Chip R max P G 2 λ EIRP Label = 2 (4 π ) PChip ϑ Matching ϑ Polarisati on ϑ Antenna Example I (UHF) under US regulations: P EIRP = 4 W; G Label = 1.64; f = 915MHz; P CHIP = 35µW ϑ Matching = 0.8; ϑ Polarisation = 1; ϑ Antenna = W m R max = = 7. 19m 2 6 (4 π ) W RFID Systems 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 ϑ Matching = 0.8 ; ϑ Polarisation = 1 ; ϑ Antenna = W m R max = = 6. 90m 2 6 (4 π ) W RFID Systems 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 RFID Systems Seite 16

17 Anti collision algorithm RFID Systems Seite 17

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

19 Tag Inventory flag RFID Systems Seite 19

20 Tag persistence RFID Systems 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 RFID Systems Seite 21

22 Environmental Influence - Overview UHF-Characteristics Absorption/Damping Reflection Refraction Diffraction Penetration into Liquids Interference Polarisation RFID Systems 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, RFID Systems 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 RFID Systems 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 RFID Systems 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 RFID Systems 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. RFID Systems 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 RFID Systems 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 RFID Systems 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 RFID Systems 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 RFID Systems 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 RFID Systems 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 RFID Systems 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 RFID Systems 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... RFID Systems 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) RFID Systems Seite 36

37 Multi Antenna Arrangements Positioning Parallel mounted Gate antennas RFID Systems 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 RFID Systems 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 RFID Systems Seite 39

40 Assembling Parasitic Capacitances C parasit C chip R C = C + tot parasit C chip RFID Systems Seite 40

41 Reference antenna design FF9510 RFID Systems Seite 41

42 FF9510 Change loop size Range [m] 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] RFID Systems Seite 42

43 FF9510 Change dipole length 7 6 dl dipole = 0 mm dl dipole = mm dl dipole = mm dl dipole = mm dl dipole = mm 5 Rang [m] L decrease Freq [GHz] RFID Systems Seite 43

44 FF9510 Change connection dipole loop Range [m] 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] RFID Systems Seite 44

45 FF9510 Total Gain 868 MHz RFID Systems 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 RFID Systems 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! RFID Systems Seite 47

48 RFID Systems Seite 48

49 Assembled die RFID Systems Seite 49

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

51 Pmin - Anechoic chamber RFID Systems Seite 51

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

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

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

55 RFID PCB Antenna Designer Target: Easy access to customized PCB antennas Supported ICs: UCODE G2iL (SL3S1203) UCODE G2iM (SL3S1013) UCODE I2C (SL3S4011) Link: direct_transim_rfid.html RFID Systems Seite 55

56 RFID PCB Antenna Designer - Design flow IC Selection Specification Synthesis EM Validation Simulation Step 1 Step 2 Step 3 Step 4 Step 5 Choice of three different RFID UHF ICs UHF frequency selection Available space for antenna Antenna type Antenna topology PCB board dimensions PCB board material Start CST Simulation After simulation report and download RFID Systems Seite 56

57 Design flow Step 1 - IC selection Supported ICs: UCODE G2iL (SL3S1203) UCODE G2iM (SL3S1013) UCODE I2C (SL3S4011) Access Product Info Access datasheet RFID Systems Seite 57

58 Design flow Step 2 - Specification UHF Selection: Region Power level Available antenna space PCB top layer type RFID Systems Seite 58

59 Design flow Step 3 - Synthesis Topology selection Topology - Geometry RFID Systems Seite 59

60 Design flow Step 4 EM Validation Board Dimensions PCB Specification RFID Systems Seite 60

61 Design flow Step 5 - Simulation Login required for starting the simulation! Simulation time counter RFID Systems Seite 61

62 Design flow Step 6 - Results Download: CST file DXF file Summary PDF Summary XLS RFID Systems Seite 62

63 Thank you for your Audience! Please feel free to ask questions... RFID Systems Seite page 63