Evolution of RFID Systems

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1 Evolution of RFID Systems Peter H Cole Adelaide Auto-ID Laboratory 23 January 2006 Evolution of RFID systems 1 1

2 Objectives Title is to capture notions of How RFID systems have evolved under constraints How they might evolve under research If desired, some details of research at Adelaide 23 January 2006 Evolution of RFID systems 2

3 Topics RFID regulations Antenna issues Propagation studies Protocol issues Higher functionality tags Signalling waveform design Security and authentication 23 January 2006 Evolution of RFID systems 3

4 RFID regulations Regulators ITU Regions ]FCC, EN, Other national bodies Usage of radio spectrum and bands Regulatory standards ISO ETSI Australia experimental licence Listen before talk regulations Synchronisation 23 January 2006 Evolution of RFID systems 4

5 Antenna issues Electromagnetic theory Coupling calculations Bode Fano Limit Antennas for dual frequencies Antenna size and frequency constraints Antennas in or near metal A small antenna example. 23 January 2006 Evolution of RFID systems 5

6 Propagation studies Electromagnetic theory Near and Far fields Near and far field coupling theories Some fundamental constraints Dense RFID reader studies. 23 January 2006 Evolution of RFID systems 6

7 Protocol issues Concept of a protocol Tag talks first and reader talks first protocols Constraints on protocols UHF signalling HF signalling Adaptive round concepts EPCglobal C1G2 protocol Approaches to advanced HF protocols Can HF sustain heavy signalling? Ways it might 23 January 2006 Evolution of RFID systems 7

8 Higher functionality tags Autonomously networking tags Merging of EAS and data tags Trigger circuits for battery tags Low power approach Issues and experiments Zero power approach Application to theft detection 23 January 2006 Evolution of RFID systems 8

9 Security and Authentication Methods for providing security Levels of security Burdens on chip design Burdens on signalling systems 23 January 2006 Evolution of RFID systems 9

10 Overview of Adelaide research Personnel Classification of projects Detector research Data logging reader research Dense reader environment research Privacy and security research Trigger circuit research Publications 23 January 2006 Evolution of RFID systems 10

11 Antenna Issues Peter H Cole Adelaide Auto-ID Laboratory 23 January 2006 Evolution of RFID systems 11 11

12 Outline Electromagnetic theory How antennas work (approximately) Near and far fields Near and far field coupling theories Significant conclusions about performance Bode-Fano limit for efficiency Some simple tag designs 23 January 2006 Evolution of RFID systems 12

13 Laws in differential form B E = - t H = J + D Vortex t D = ρ B = 0 Source 23 January 2006 Evolution of RFID systems 13

14 Boundary Condition: electric field Electric field Charge Conducting surface 23 January 2006 Evolution of RFID systems 14

15 Boundary Condition: magnetic field Magnetic field or displacement current Conducting plane 23 January 2006 Evolution of RFID systems 15

16 The basic laws: how they work Gauss s law Electric flux deposits charge Electric field cannot just go past a conductor, it must turn and meet it at right angles Faraday s law Oscillating magnetic flux induces voltage in a loop that it links + _ V B 23 January 2006 Evolution of RFID systems 16

17 23 January 2006 Evolution of RFID systems 17 Fields of a Magnetic Dipole (oh dear) θ β β π β β cos ) ( 2 ) ( r j r e r j r M j H = θ β β β π β β θ sin ) ( ) ( 1 ) ( r j e r j r r j M j H + = θ β β π β β φ sin ) ( 1 ) ( r j e r r j M j E + =

18 Near and far field coupling theories Common feature: a label driving field is created, how much signal can be extracted? In the near field of the interrogator, the driving field is mostly energy storage, and the amount radiated does not affect the coupling, but does affect the EMC regulator. Various techniques to create energy storage without radiating are then applicable. Some theorems on optimum antenna size are of interest. In the far field of the interrogator, the relation between what is coupled to and what is regulated is more direct, and such techniques are not applicable. 23 January 2006 Evolution of RFID systems 18

19 23 January 2006 Evolution of RFID systems 19 Far field coupling theory r e r r S g A S P π λ 4 2 = = 2 t 4 Power flow per unit area r P g t π = Power flow per unit area = er P r A π λ 4 2 r er g A = 2 4 = r g g P P t r t r π λ

20 Near field coupling theory V c = [ Reactive power flowing in the untuned label coil when it is short circuited] [ Volume density of reactive power created by the interrogator at the label position] V d = [ Reactive power flowing in the inductor of the interrogator field creation coil ] [ Volume density of reactive power created by the interrogator at the label position] P P V 2 c = Q1Q 2 1 Vd 23 January 2006 Evolution of RFID systems 20

21 Measures of exciting field In the far field W = βs v r 23 January 2006 Evolution of RFID systems 21

22 Significant conclusions Coupling volumes for well shaped planar electric and magnetic field labels are size dependent and similar Magnetic Radiation quality factors for both types of label formed within a square of side L are size dependent and similar Magnetic V c = Q r = L ( ) 3 β L Electric Electric Q r = V c = These are calculated results for sensibly shaped antennas 2L ( β L) 3 23 January 2006 Evolution of RFID systems 22

23 Optimum operating frequency The optimum frequency for operation of an RFID system in the far field is the lowest frequency for which a reasonable match to the radiation resistance of the label antenna can be achieved, at the allowed size of label, without the label or matching element losses intruding. 23 January 2006 Evolution of RFID systems 23

24 Bode-Fano Limit RS VS ZIN LOSSLESS MATCHING NETWORK C R 0 ln 1 Γ dω π RC 23 January 2006 Evolution of RFID systems 24

25 Bode-Fano Limit (cont) Reflection coefficient, Γ 1 Γ inband ω ω 1 2 ω Angular frequency, ω Γ 1 2 frc e inband 23 January 2006 Evolution of RFID systems 25

Bode-Fano Limit (cont) Allocated bandwidths for RFID: Others: China: 917 922 MHz (Temporary

26 Bode-Fano Limit (cont) Allocated bandwidths for RFID: Others: China: MHz (Temporary license can be applied) Australia: MHz 23 January 2006 Evolution of RFID systems 26

27 Bode-Fano Limit (cont) 3 different cases considered: Reflection coefficient, Γ 1 Γ max Reflection coefficient, Γ 1 Γ max f Frequency, f (in MHz) (a) f 1 f 2 f 3 Frequency, f (in MHz) (b) Reflection coefficient, Γ 1 Γ max f Frequency, f (in MHz) 23 January 2006 Evolution (c) of RFID systems 27

28 Bode-Fano Limit (cont) Assume R = 1 kω, C = 1 pf R = 10 kω, C = 1 pf (for less power consuming tag chip in practice) 23 January 2006 Evolution of RFID systems 28

29 A Simple RFID Tag Consists of a circular loop antenna with a very simple matching network FRONT REAR 23 January 2006 Evolution of RFID systems 29

30 Higher Functionality Tags Adelaide Auto-ID Laboratory 23 January 2006 Evolution of RFID systems 30 30

31 Interesting questions Merging of EAS and Data tags Turning on battery operated tags Low power consumption Zero power consumption 23 January 2006 Evolution of RFID systems 31

32 Transmitter operated systems Some small voltage is generated form transmitted power A low power consumption circuit detects that event Quality factor issues arise R r R l Label antenna jx s Junction capacitance jx l D.C. output line R a jx B Bypass and reservoir capacitance Resonant circuit 23 January 2006 Evolution of RFID systems 32

33 Experiments on detuning 1MΩ 10kΩ 11.5pF RF IN through an SMA connector Rectified voltage to Oscilloscope using a BNC connector 23 January 2006 Evolution of RFID systems 33

34 Low and high power sweeps 23 January 2006 Evolution of RFID systems 34

35 A low voltage turn on circuit Sensitivity about 5 mv Power consumption few na 23 January 2006 Evolution of RFID systems 35

36 Zero power turn on concept Low frequency magnetic field vibrates a magnet Piezoelectric converter generates about a volt 23 January 2006 Evolution of RFID systems 36

37 Electroacoustic conversion modelling Variables are Torque and angular displacement, charge and voltage Electroacoustic parameters for substances known Parameters for structures are calculated therefrom + _ q Electroacoustic 1 energy conversion system 2 + _ 23 January 2006 Evolution of RFID systems 37

38 23 January 2006 Evolution of RFID systems 38 Eletroacoustic conversion Structural parameters appear below = τ φ θ P P P P C C C C q

39 Structure analysed Magnet Piezoelectric material F w P h F t p t m 23 January 2006 Evolution of RFID systems 39

40 Result Turn-on voltage depends on Driving magnetic field Electroacoustic parameters Some resonance quality factors V TO = k 2 Q 2 Mv 2 2 C 2 1 ( µ ) H m 0 22S C C eff J 22eff 23 January 2006 Evolution of RFID systems 40

UNIVERSITY OF BOLTON. SCHOOL OF ENGINEERING, SPORTS and SCIENCES BENG (HONS) ELECTRICAL & ELECTRONICS ENGINEERING EXAMINATION SEMESTER /2018

UNIVERSITY OF BOLTON. SCHOOL OF ENGINEERING, SPORTS and SCIENCES BENG (HONS) ELECTRICAL & ELECTRONICS ENGINEERING EXAMINATION SEMESTER /2018 ENG018 SCHOOL OF ENGINEERING, SPORTS and SCIENCES BENG (HONS) ELECTRICAL & ELECTRONICS ENGINEERING MODULE NO: EEE6002 Date: 17 January 2018 Time: 2.00 4.00 INSTRUCTIONS TO CANDIDATES: There are six questions.