Design of RFID Tags and Systems

Transcription

1 Design of RFID Tags and Systems Dr. KVS Rao Intermec Technologies Everett, WA, USA Prof. Raj Mittra Pennsylvania State University University Park, PA, USA June 10, 007 APS 007 Honolulu, Hawaii

2 Contents 1. Introduction to RFID. RFID link budget and backscattering fundamentals 3. RF front end considerations of ASIC. 4. RF matching from ASIC to antenna 5. Complete design, simulation and test of RFID tag, including antenna, ASIC and application examples 6. Near-field antenna considerations for RFID tags 7. RFID applications, examples, and latest developments 8. Conclusions

3 1. Introduction to RFID Operating principles History RFID systems Frequencies Tags Readers Protocols

4 RFID Technology RFID (Radio Frequency Identification) uses radio frequencies for sending data from the tagged object to the reader. RFID system components Tags Readers Middleware

5 Operating Principle: LF/HF RFID LF/HF low and high frequency Reader coil antenna creates RF magnetic field Passive tag gets power from the energy of the field responds by loading its own coil antenna with different impedances Analogy: loaded transformer

6 Operating Principle: UHF RFID UHF ultra high frequency Antenna Reader antenna transmits RF signal for the tag Passive tag gets power from the energy of the received signal and reflects it, modulating with its own impedance and thus presenting different RCS values Analogy: using flashlight and mirror to communicate with Morse code

7 World War II History of RFID German pilots rocked their planes to signal back to the radar that they are coming British aviation used identify friend or foe system with simple transponder in the nose of the plane 1945 Soviet eavesdropping device Buran (Leo Theremin) paper Communication by means of reflected power (Harry Stockman) 1973 first RFID patent 1999 Auto-ID center is formed at MIT 004 EPC Gen standard is ratified

8 RFID vs. Bar Code RFID tag Bar code Rewriteable Yes No Read distance Up to 30 ft Up to 3 ft Line of sight Not necessary Necessary Read speed Reliability Up to 1500 tags/sec (Gen) Difficult to damage and counterfeit bar codes/sec (trained operator) Easy to damage and counterfeit Cost $ $ Equipment cost Approximately the same

9 RFID Frequency Bands LF HF UHF Frequency KHz MHz MHz Standards Read range Data rate ISO 11784/5 ISO 143 ISO up to 1 m up to 9600 bps ISO ISO ISO up to 1m up to 64 kbps ISO up to 15 m up to 640 kbps Applications Logistics, manufacturing, access control 100 khz 1 MHz 10 MHz 100 MHz 1 GHz 10 GHz LF MF HF VHF UHF khz MHz 915 MHz.45 GHz

10 UHF Tag Classification By power Passive Semi-passive Active By memory Chipless (read only) With chip Class 0 Class 1 ISO ( B), Gen (ISO C) Tag evolution

11 Flexible Passive UHF Tags Used in smart labels

12 Rigid Passive UHF Tags Used for tagging pallets, machine parts, metal objects

13 RFID Readers and Printers Readers Direct conversion transceivers, simultaneous Tx/Rx Antennas: separate (switching) or single Power: up to 1 W (30 dbm) Sensitivity up to -80 dbm Dynamic range up to 100 db Wireless or wired database interface Printers Reader integrated into the printer Print bar code/text/images on the label and encode RFID inlay

14 UHF RFID Protocols Class 0 Class 1 ISO-6B Gen (ISO-6C) Anticollision method Binary Binary Binary Aloha Read rate Low Low Low High Password No No No Write/read/kill Group select No No No Yes Read/write No Limited Yes Yes Encryption No No No Reader

15 Gen Electronic Product Code (EPC) 96 bit (4 hexadecimal symbols) Header (8 bit): version number 56 combinations EPC manager number (8 bit): manufacturer 68 million combinations Object class number (4 bit): type of product 16 million combinations Serial number (36 bit): unique 68 billion combinations User data (3 bit).

16 References H. Stockman, Communication by means of reflected power, Proc. IRE, pp , Oct A. R. Koelle, S. W. Depp, and R. W. Freyman, Short-range radio-telemetry for electronic identification, using modulated RF backscatter, Proceedings of the IEEE, vol. 63, no. 8, Aug. 1975, pp R. Glidden, et al., Design of ultra-low-cost UHF RFID tags for supply chain applications, IEEE Communications Magazine, vol. 4, no. 8, Aug. 004, pp J. Landt, The History of RFID, IEEE Potentials, vol. 4, no. 4, Oct.-Nov. 005, pp R. Want, An Introduction to RFID Technology, IEEE Pervasive Computing, vol. 5, no. 1, Jan.-Mar. 006, pp. 5-33

17 . RFID Link Budget Calculations and Backscattering Fundamentals Link budget Tag read range Definition Limitations Measurement RCS (Radar Cross Section) Scalar RCS Differential RCS Scalar Vector

18 Link Budget Power received by tag antenna in free space (from Friis equation) P a = P G t t λ, r 4πd ( θ ϕ) G ( θ, ϕ) p Pa power received by tag antenna Pt reader output power Gr gain of the reader antenna Gr gain of the tag antenna p polarization mismatch loss λ wavelength d distance to the tag

19 Tag Read Range Power absorbed by the chip is determined by impedance matching P c = P a τ Chip must receive enough power to turn on: Pc P th Maximum read range r = λ π PG G τ p t t r 4 Pth τ power transmission coefficient (a.k.a.impedance matching coefficient) P th power threshold of IC

20 Tag Read Range and Read Rate 90 % Read rate in a typical RFID system depends on distance and frequency (figure above is for the case where a tag is tuned to 900 MHz in a specific environment)

21 Tag Read Range Depends on the following factors: Tag Chip sensitivity Antenna gain Impedance matching Polarization matching Channel Propagation loss Reflections Interference Reader Transmitter power Receiver sensitivity Tag antenna impedance and gain depend on the properties of tagged object Interference from other wireless sources can significantly degrade tag range. Ideally, RFID reader detects the tag as soon as it responds.

22 Tag Limitations Tag must provide strong modulated backscattered signal for the reader P backscattered G r G r gain of the tag antenna K modulation loss Two tags may have the same maximum range but signals seen by the reader from these tags may be different Tag 1 Antenna gain = 0 dbi Chip sensitivity = -10 dbm Maximum range = 16 ft (900 MHz, 4 W EIRP) Tag Antenna gain = 10 dbi Chip sensitivity = 0 dbm Maximum range = 16 ft (900 MHz, 4 W EIRP) P 1 P = backscatte red backscattered 0 db!

23 Propagation Environment Limitations Path loss Free space Multi-path environment Waveguide environment Tag detuning on materials Antenna impedance Antenna gain

24 Reader Limitations EIRP (US: 4 W, Europe: 3.3 W) Sensitivity (equivalent) Reader must be able to detect and decode noisy tag signal whose SNR proportional to tag differential RCS Gen 0.06 Voltage (V) Time (us)

25 Example 4 W EIRP 915 MHz -80 dbm equivalent sensitivity Free space -10 dbm chip sensitivity dbi antenna perfect impedance match 3 db modulation loss

26 Example Transmitted EIRP (36 dbm) 0 ft Typical tag chip sensitivity (-10 dbm) 10 ft Typical reader sensitivity (-80 dbm) Received power vs. distance for tag and reader in example RFID system

27 Tag Range Measurement Procedure Distance d to the tag is fixed, transmitted power is variable Test equipment sends queries and analyzes backscattered signal Minimum power Pmin at which tag response is detected allows one to determine tag range at different frequencies for any given EIRP value r = d EIRP P min

28 Range Measurement Facility at Intermec Anechoic chamber 4 ft x 4 ft x 6 ft 6 dbi linearly polarized antenna

29 Measurement Equipment National Instruments PXI RF hardware platform controlled by LabVIEW Measures the minimum power needed for tag to respond Multi-protocol (ISO, Gen, etc.) Broadband ( MHz)

30 RFID Tag Scalar RCS Scalar RCS of an RFID tag determines the backscattered power when the tag antenna loaded with constant impedance load Backscattered power = Power scattered from the opencircuited antenna + Power re-radiated by the loaded antenna Open-circuited thin wire antennas scatter little power compared to when they are loaded (minimum scattering) For minimum scattering loaded antennas, re-radiated power can be calculated from the simple equivalent circuit σ = P S backscattered incomin g P power S power density P backscattered = P open circuited + P re radiated P re radiated

31 Scalar RCS Derivation Power collected by the loaded antenna P a = S A e = PG t t λ G 4π r 4π Power re-radiated by the loaded antenna (power dissipated in Za) G gain of the tag antenna A t e PG antenna effective area transmitt ed EIRP λ wavelength Z Z c a t = R = R c a + jx + jx c a chip impedance antenna impedance P = P 4Ra + Z re radiated a Z a c G Scalar radar cross-section σ P re radiated = S λ G R = π Z + Z a a c

32 K-factor K-factor shows how much power is re-radiated K = Z a 4R + a Z c * Z c 0 Z a R 4R a + a K 1 0 X a Power re-radiated by complex conjugate loaded antenna is normalized by the power re-radiated by the short circuit loaded antenna

33 Measurement Methodology Anechoic chamber, antenna, network analyzer, tag tester Return loss is measured without a tag (for calibration) and then with the tag present inside the chamber Antenna RFID tag Antenna gain is 6 dbi, distance to the tag is 0.5 m (to power up tag IC)

34 Tags used in Measurements 16 mm

35 Return Loss Calibration (without Tag)

36 Measured Return Loss (with Tag) RFID tag scalar RCS σ = S 11 ( 4π ) λ 3 r G t 4

37 Comparison of Theory and Data

38 RFID Tag Differential RCS Differential RCS of an RFID tag is an important parameter which determines the power of the modulated tag signal received by the reader Non-coherent receiver can only register a magnitude difference between two scalar RCS values (scalar differential RCS) Coherent receiver can detect both amplitude and phase of the signal and hence can register a vector difference between two RCS values (vector differential RCS

39 Vector Differential RCS Derivation Currents in the antenna due to two different loads Differential backscattered power I P dif. bs. o ( Z + Z ) o 1,. = = 1 a = V 1 c1, I 1 I R V a R ( ρ ) a G 1, RFID tag differential RCS Δσ = P dif. bs. S = λ G 4π ρ 1 ρ Load reflection coefficient ρ = Z Z c1, c1, + Z Z * a a

40 Vector Differential RCS on Smith Chart ρ = Z Z c1, c1, + Z Z * a a

41 Measurement Setup Received power is measured directly in the signal analyzer Δσ = P PG received t t ( 4π ) 3 λ d 4

42 Comparison of Theory and Data -0 Theory differential RCS (dbsqm) Data Frequency (MHz)

43 References D. D. King, The measurement and interpretation of antenna scattering, Proc. IRE, 1949, 37, (7), pp R. Harrington, Electromagnetic scattering by antennas, IEEE Transactions on Antennas and Propagation, 1963, 11, (5), pp R. C. Hansen, Relationships between antennas as scatterers and as radiators, Proceedings of the IEEE, 1989, 77 (5), pp K. Schneider, A re-look at antenna in-band RCSR via load mismatching, Proc. of IEEE Ant. and Prop. Soc. Int. Symposium, June 1996, pp L. Penttila, M. Keskilammi, L. Sydanheimo, and M. Kivikoski, Radar crosssection analysis for passive RFID systems, IEE Proceedings on Microwaves, Antennas and Propagation, 006, 153, (1), pp P. V. Nikitin and K. V. S. Rao, Theory and measurement of backscattering from RFID tags, IEEE Antennas and Propagation Magazine, vol. 48, no. 6, pp. 1-18, December 006 P. V. Nikitin, K. V. S. Rao, and R. Martinez, Differential RCS of RFID tag, Electronics Letters, vol. 43, no. 8, pp , April 007

44 3. RF Front End Considerations of ASIC Tag Block Diagram Rectifier and Voltage Multiplier Modulator and Demodulator Tag Equivalent Circuit Example Design Criteria

45 Tag Block Diagram Detects signal envelope for data decoding Supplies DC voltage Changes tag input impedance

46 Rectifier and Voltage Multiplier V OUT ( V ) N V RF D V OUT V RF N V RF V D - number of diodes - amplitude of RF input signal from tag antenna - forward voltage of Schottky diodes (~0.V)

47 Modulator and Demodulator Antenna terminals Modulator Antenna terminals Demodulator

48 Tag Equivalent Circuit Example

49 Front End Impedance Calculation Impedance calculation of the front-end (ohms) : 10 3 i R pad := 10 C pad :=.0991 Z pad := R pad + R s := 13 R j := C j :=.0 π f r C pad 10 3 i R nwell := 100 C nwell :=.074 Z nwell := R nwell + π f r C nwell 1 1 Z pwrpt := Z diode + Z sigpt := Z diode ( 10) 3 i π 15 f r 1 Z diode := R s R j 1 ( 10) 3 i π 1.5 f r ( 10) 3 i π f r C j Z sp := π i f r 1. 1 Z chip := Z pad Z nwell Z diode + 1 Z pwrpt + 1 Z sigpt Z chip = i

50 Package Impedance Calculation and Matching Z tag := i Parameters of the package : C pkg :=.085 L pkg := 1.5 X L := π f r L pkg i Z t4 := 0 + π 10 3 f r C pkg i Z cfl := Z chip + X L Z 11 := Z t4 + X L Z 1 := Z t4 Z 1 := Z 1 Z := Z 11 Z 1 Z 1 Z pkg := Z 11 + ( Z Z chip ) Z pkg = i Ratio := ( Z chip ) Re( Z chip ) Re( Z pkg ) ( Z pkg ) Ratio = 1.08 Z pkg 50 τ pkg := Z pkg + 50 Z tag 50 τ tag := Z tag + 50 τ pkg = τ tag = Z pkg = i This mismatch can be calculated from the transmission coefficient which can be expressed as τ := ( ) 4 Re Z pkg Z pkg Re( Z tag ) ( + ) Z tag τ := ( ) ( ) 1 τ tag 1 τ pkg ( 1 τ tag τ pkg ) τ = Mismatch loss in db is : ML := 10 log() τ ML = 0.954

51 Front End Design Considerations Rectifer/voltage multipler Forward link limitation on tag range Having a high RF to DC power conversion efficiency Providing sufficiently high output voltage (~ V) to power up digital logic Modulator Return link limitation on tag range Choosing the modulation type Selecting the impedance states to achieve high modulated backscattered power

52 References U. Karthaus and M. Fischer, Fully integrated passive UHF RFID transponder IC with 16.7 u/w minimum RF input power, IEEE Journal of Solid-State Circuits, Volume 38, Issue 10, Oct. 003, pp G. De Vita and G. Iannaccone, Design Criteria for the RF Section of UHF and Microwave Passive RFID Transponders, IEEE Transactions on Microwave Theory and Techniques, vol. 53, no. 9, Sept. 005, pp J.-P. Curty, N. Joehl, C. Dehollain, and M. J. Declercq, Remotely powered addressable UHF RFID integrated system, IEEE Journal of Solid-State Circuits, Volume 40, Issue 11, Nov. 005, pp

53 4. RF matching from ASIC to antenna Equivalent Circuit Power transmission coefficient Impedance contours Normalized contours Reflection coefficient Smith chart

54 Tag Equivalent Circuit Power absorbed by the chip is determined by impedance matching P c = P a τ τ = Z 4R c + c R Z a a Antenna Pc power absorbed by the chip P power availabe from the antenna a τ power transmission coefficient Z Z c a = R = R c a + jx + jx c a chip impedance antenna impedance Chip

55 Impedance Matching Contour Chart Impedance Matching Contour Chart ( ) ( ) τ τ τ = + + c c a c a R X X R R 4 a c a c Z Z R R + = τ ( ) ( ) τ a c a c a c R R X X R R 4 = Contours of constant transmission coefficient are circles on (Ra,Xa) plane Center of circles corresponds to perfect match Circle radius depends on chip impedance 1 τ R c X a τ τ 1 c R =1 τ

56 Normalized Impedance Matching Contour Chart Normalized Impedance Matching Contour Chart ( ) ( ) τ τ τ = + Q x r a a 1 τ ( ) ( ) τ a a a r Q x r 4 1 = + + Contours of constant transmission coefficient are circles on (ra,xa) plane Center of circles corresponds to perfect match Circle radius depends only on transmission coefficient Q τ τ 1 ( ) ( ) 1 4 a a a x Q r r = τ c c c a c a R X R X R R = = = Q x r a a =1 τ

57 Complex Impedance Matching on Smith Chart Complex Impedance Matching on Smith Chart c a c a Z Z Z Z + = * ρ ( ) ( ) c c a a c c a a R X X j R R X X j R = ρ Smith chart is normalized to real impedance Rc Quantity plotted is Ra+j(Xa+Xc) Origin corresponds to perfect match 1 ρ τ =

58 Range vs. Transmission Coefficient r τ Shows the effect of better matching on relative range improvement Maximum possible range is when the tag is perfectly matched

59 References K. Kurokawa, Power waves and the scattering matrix, IEEE Transactions On Microwave Theory and Techniques, 1965, MTT- 13, (3), pp K. V. S. Rao, H. Heinrich, R. Martinez, On the analysis and design of high-performance RFID tags," IEEE Workshop on Automatic Identification Technologies, pp , March 00 P. V. Nikitin, K. V. S. Rao, S. Lam, V. Pillai, R. Martinez, and H. Heinrich, Power Reflection Coefficient Analysis for Complex Impedances in RFID Tag Design, IEEE Transactions on Microwave Theory and Techniques, vol. 53, no. 9, pp , September 005

60 5. Complete Design, Simulation and Test of RFID Tag, including Antenna, ASIC and Application Examples Tag design process Tag characteristics Performance chart Design examples

61 RFID Tag Design: Art or Science? Most flexible tags are dipoles (folded, loaded, stubbed, meandered, fed with slotline, crossed, combined with loops, etc.)

62 RFID Tag Materials Dielectric Substrate FR4 (rigid) PET (flexible) High permittivity dielectrics Paper Antenna Trace Copper (most expensive) Aluminum (less expensive) Silver ink (cheapest) Chip packaging Flip-chip Wire-bonded SMD packages (TSSOP, MSOP)

63 RFID Tag Design Process Select the application and define tag requirements Determine the materials for antenna construction Determine RF impedance of packaged ASIC Identify the type of antenna and its parameters Perform parametric study and optimization Build and measure prototypes Design requirements met? Design is ready

64 EM Software used at Intermec Pallet tag Ansoft HFSS Thick (rigid) tags, chip packaging modeling Designer Thin (flexible) tags Rigid tag Meander tag

65 Main Tag Characteristics Range Bandwidth Omni-directionality

66 Tag Antenna Performance Chart ro - range of the tag with 0 dbi antenna and perfect impedance match

67 RFID Tag Design Example Requirements RFID tag for smart label applications on variety of materials Range: at least 15 ft in MHz band (free space, 4W EIRP) Size limitation: 4 x 4 in Materials: 1 mil copper on mil polyester substrate Chip: ISO B Attachment: flip-chip, packaging variations possible S-structure Wideband Tag antenna Tunable to accommodate for: Chip packaging variations Different tagged materials

68 Packaged Chip Impedance Theoretical Modeling/simulation with HFSS TSSOP Flip-chip Practical Measure packaged chip impedance at different power levels with a network analyzer

69 Chip Impedance vs. Frequency and Power Frequency dependence Power dependence R Impedance of RFID Gen Chip (-10 dbm) Xj Frequency R(Ohms) R Impedance of RFID Gen Chip (Freq 900) Power Delivered to Chip (dbm) Xj R(Ohms)

70 Tag Design Process with Designer Create parametric geometry Specify excitation Write post-processing variables

71 Parametric Study Identify key parameters and fix others Run parametric analysis, plot and examine the range Identify optimal parameter combinations

72 Parametric Study (S-antenna) Fixed parameters L=H=80 mm W1=0.5 mm Variable parameters W=W3=W L3 Optimal parameter combination W=10 mm L3=80 mm (untrimmed), 40 mm (trimmed for 915 MHz band) L3 varied W varied

73 Experimental Verification Make several prototypes (use X-acto knife) Compare with experimental data Identify sources of discrepancy 30 5 L3 = 40 mm Range (ft) Data Simulation Free space, 4 W EIRP Frequency (MHz) Designer simulation has frequency offset compared to data (HFSS agrees with data well)

74 Final Design of S-antenna* Prototype Tuning by trimming (punching) 10 mm 10 mm 80 mm Gain pattern 0.5 mm 80 mm * patent pending

75 Performance on Different Materials 30 L3 = 40 mm Free space, 4 W EIRP 5 0 Range (ft) Free space Cardboard Plastic Minimum required range Frequency (MHz) S-antenna tag can be easily tuned for any material

76 Another Design Example Intellitag ID card 915 MHz band ISO B 70 mm x mm 4 mil FR4 substrate with copper trace Fairchild RFID ASIC chip Antenna was modeled and simulated with Ansoft Designer

77 Experimental and Simulation Results EIRP=4 W Resonant frequency inside plastic card Free space resonant frequency RFID tag characteristics depend on surrounding material

78 References P. R. Foster and R. A. Burberry, Antenna problems in RFID systems, IEE Colloquium on RFID Technology, October 1999, pp. 3/1-3/5 K. V. S. Rao, P. V. Nikitin and S. Lam, Antenna Design for UHF RFID Tags: a Review and a Practical Application, IEEE Transactions on Antennas and Propagation, vol. 53, no. 1, pp , December 005 D. M. Dobkin and S. M. Weigand, UHF RFID and tag antenna scattering (Part I: Theory, Part II: Experimental Results), Microwave Journal, vol. 49, no. 5-6, May-June 006 T. C. Chau, B. A. Welt, and W. R. Eisentadt, Analysis and Characterization of Transponder Antennae for Radio Frequency Identification (RFID) Systems, Packaging Technology and Science, no. 19, pp , 006

79 6. Near-field Antenna Considerations for RFID Tags Antenna field regions Reader-tag antenna coupling Material penetration and antenna size Near Field UHF RFID Options Measurements

80 Antenna Field Regions Reactive Antenna RFID reader D r Reactive near field Radiating near field Electrically small antenna r r = λ / π λ / π Electrically large antenna r = r < 0.6 D 3 D / λ / λ Near-field theory is the same for LF, HF, and UHF RFID (comes from Maxwell s equations)

81 Reader-Tag Antenna Coupling 4 R r R c a t ρ = Pchip = Preader ρ C τ τ = Z r + Z Reader impedance matching coefficient t Coupling coefficient C depends on: Reader and tag antenna geometries; Relative position of antennas (distance and orientation); Environment, including any objects near antennas. Z 4R c + R Z a Tag impedance matching coefficient

82 Types of Coupling Radiative (far field) Non-radiative (near field) Inductive (magnetic) Capacitive (electric) Different regions of reader antenna impedance (shown for a dipole antenna).

83 Hertzian Dipole FIelds Hertzian Dipole FIelds θ β β π β η β cos ) ( 1 ) ( 1 3 r j r e r j r j l I E + Δ = θ β β β π β η β θ sin ) ( 1 ) ( r j e r j r j r j l I E + + Δ = θ β β π β β φ sin ) ( r j e r j r j l I H + Δ = Near field decays as 1/r^ and 1/r^3 Far field decays as 1/r x E z Energy radiation Energy storage r r E H Near field Far field

84 Far Field Coupling (Radiative) Mutual effect of antennas is minimal Antenna impedance and gain can be specified independently of each other and of distance between the antennas Long range, associated with electromagnetic plane waves Reader transmits a modulated signal which decays in free space as 1/r Tag responds by modulating the backscattered signal from the tag C = G L t path G r p In free space, path loss is: RFID reader RFID tag λ L path = 4π d

85 Near Field Coupling (Non-radiative) Mutual effect of antennas cannot be ignored Antenna impedance and gain become dependent on mutual antenna position and orientation Inductive Coupling (magnetic): most energy is stored in magnetic field Example: multiple turn coil, axial magnetic field decays as 1/r^3 RFID application: HF RFID systems Field is mostly affected by the presence of magnetics and conductors Capacitive Coupling (electric): most energy is stored in electric field Example: parallel plate capacitor RFID application: UHF RFID printer coupler Field is mostly affected by the presence of dielectrics and conductors

86 Magnetic Coupling Example (HF RFID) Basic theory: Faraday s law (induced voltage is proportional to the magnetic flux rate of change) V If the tag antenna is small, the magnetic field created by the reader antenna is not perturbed by the tag and the coupling coefficient is: C dφ = dt f N S B α RFID reader antenna RFID transponder

87 Material Penetration and Antenna Size Field penetration into materials is limited by skin depth For near field operation antenna size can be much smaller than wavelength To radiate efficiently into the far field, antenna size needs to be comparable with wavelength δ = 1 π μ σ f μ permeability σ conductivity f frequency Frequency 15 KHz (LF) MHz (HF) 900 MHz (UHF) Wavelength 400 m.1 m 0.33 m Skin depth (aluminum) 30 um.3 um.7 um

88 Item Level UHF RFID System Options Reader Antenna Reader Power Tag Read zone 1 Standard Full Standard Large Standard Low Standard Small 3 Standard Full Short range Small for short range tags 1.Mistuned Large for standard tags.special 4 Special Any Special Small Standard RF antennas which radiate well into the far field Special RF antennas which generate primarily near field

89 Tag Range for Option (Low Reader Power) 8 4 Tag range (ft) EIRP=4 W EIRP=0.04 W Frequency (MHz) RFID tag: TI Dallas

90 Experimental Test Setup Inside anechoic chamber Antenna (Sinclair LPD) Tag (TI Dallas)

91 Minimum Power vs. Distance Minimum power (dbm) Frequency (MHz) d (in) RFID reader antenna: Sinclair, RFID tag: TI Dallas

92 Far Field Boundary Minimum power (dbm) Theory (far field) Data Distance (in) Reader antenna: Sinclair, RFID tag: TI Dallas

93 Liquids Demo: UHF RFID Tag in Gatorade Standard UHF RFID reader antenna Standard UHF RFID tag Tag is immersed into the bottle of Gatorade

94 Liquids Demo: Measurement Results 8 Tag response 7 Power (dbm) Frequency (MHz) Tag can be read using as little as 50 mw reader power at 890 MHz

95 Near Field UHF RFID Tags LF and HF RFID Tags can not work in far field Physical sizes of the antenna ( both reader and tag) need to be large to operate in far field UHF RFID Tags can work both in near and far field Radiation mechanism includes both near and far fields for realizable physical sizes of the antenna (both reader and tag)

96 Near Field Considerations Basic physics and design methodology are the same for RFID at LF, HF, and UHF Near field UHF RFID can be used for item level tagging Magnetic or electric coupling can be used for near field UHF RFID depending on application UHF has the advantage of smaller antenna size for both near and far field operation

97 References C. A. Balanis, Antenna theory: analysis and design, John Wiley & Sons, 1997 R. Bansal, Near-field magnetic communication, IEEE Antennas and Propagation Magazine, Vol. 46, No., Apr. 004, pp Item-level visibility in the pharmaceutical supply chain: a comparison of HF and UHF RFID technologies, white paper by Philips, TAGSYS, and Texas Instruments, available at Philips-White-Paper.pdf T. Lecklider, The world of the near field, Evaluation Engineering, October 005, available at orld.asp P. V. Nikitin and K. V. S. Rao, An Overview of Near Field UHF RFID, IEEE RFID Conference, Grapevine, TX, March, 007, pp

98 7. RFID Applications, Examples, and Latest Developments Applications Examples Latest Developments

99 RFID Applications Aviation Logistics Manufacturing Access control Anti theft Wireless pay systems Documents/cards Automobile industry Pharmaceuticals

100 Application: Supply Chain Logistics RFID portals Dock-systems Doors Bays RFID forklifts and loaders Large retailers (Wal-Mart, Target, Metro) operate on profit of less than 5% Saving only 1% significantly increases their competitiveness

101 Application: Border Control Program NEXUS US-Canada border Special lane for owners of NEXUS pass (plastic card with photograph and RFID tag) Equipment and tags are supplied by Intermec

102 Application: Airports Passenger registration, passport control, passenger tracking Baggage and cargo tagging

103 Application: Airplane Boeing 787 Dreamliner will have RFID tags on ~000 critical (expensive or requiring frequent or regular servicing) parts RFID for part tracking Reduces time for: Part identifications Locating spare parts Service document writing Prevents usage of counterfeit and used parts Allows to control part assembly procedure

104 Application: ID Cards Badges and ID cards Gen 869 or 915 MHz Read range up to 10 m

105 Latest Developments UHF Near Field RFID Tags can work close to metal/liquids Companies: Smartcode, RsiID Multi-protocol tags Single tag (multi-protocol IC with special antenna) can work in several bands (LF, HF, UHF) Companies: TwinLinx, Texas Instruments RFID Reader Chipsets Several chips do most of RFID reader functions Companies: Intel, WJ, Anadigm Organic/polymer electronics Low cost, printable, biodegradable tags Companies: OrganicID, PolyIC, ORFID

106 8. Conclusions RFID tag antenna design is both art and science Best results are obtained when tag antenna gain is maximized and tag antenna is well matched to ASIC EM software tools are necessary for RFID tag design modeling and optimization Accurate wideband tag range measurement capability is crucial for quality tag design implementation and performance verification

107 Thank you! Questions?