Tag Master Training 2013 RFID Theory VAC Tag

Tag. Master Training 2013 RFID Theory VAC Tag. Master AB Tag. Master Training Module T 1, Page 1

Contents § § § § Tag. Master AB Definition of RFID Different types of RFID History of RFID System Radio Waves Radio Regulations Safety and Health Tag. Master Training Module T 1, Page 2

Definition of RFID ”Radio-frequency identification (RFID) is a technology that uses communication via radio waves to exchange data between a reader and an electronic tag attached to an object, for the purpose of identification and tracking. ” (Wikipedia) Tag. Master AB Tag. Master Training Module T 1, Page 3

Classification of RFID Systems § Frequency § § § Tag Power Source § § Passive Semi passive Active Tag Reader Protocol § § Tag. Master AB 125/134 k. Hz 13. 56 MHz 860 960 MHz 2. 4 GHz 5. 2 5. 8 GHz Requirements Standard or Proprietary Tag. Master Training Module T 1, Page 4

RFID Frequencies § § § LF and HF systems are short range systems (1 cm – 3 m). They are for example used in proximity cards for access control and for tracking of animals and library books. UHF and SHF systems have longer read range (5 m 50 m) and are mainly used for item tracking and identification. Tag. Master provides systems for 860 960 MHz and 2. 45 GHz. 860 960 MHz 2. 45 GHz 13. 56 MHz 125 134 k. Hz LF 30 k. Hz Tag. Master AB MF 300 k. Hz HF 3 MHz 5. 8 GHz VHF 30 MHz UHF 300 MHz SHF 3 GHz 30 GHz Tag. Master Training Module T 1, Page 5

Passive, Semi-Passive, and Active Tags § Passive § § § Semi Passive § § § No transmitter (backscattering) No battery (powered from RF field) No transmitter (backscattering) Battery to power logic Active § § Active transmitter Battery to power logic and radio Exercise: 1. Compare with a flashlight and a mirror 2. How does this affect tag price, lifetime predictability & read range? Tag. Master AB Tag. Master Training Module T 1, Page 6

Tag-Reader Protocols § The protocol defines how the reader and the tag communicates § Compromise of different requirements § § § § Standard or Proprietary § § Tag. Master AB Maximum number of tags that can be read "simultaneously" Time it takes to read a single or a large number of tags Data rate between tag and reader Maximum number of readers in close proximity Power consumption of tag Reading range Standard procotols such as EPC Gen 2 makes it possible to buy readers and tags from different manufacturers. This can make things cheaper but not always optimized for specific requirements. Proprietary systems can be optimized for special applications. Tag. Master Training Module T 1, Page 7

History of RFID - Part 1 (History of Radio) 1865 1888 1893 1895 Tag. Master AB James Clerk Maxwell theoretically predicted the existence of electromagnetic waves Heinrich Hertz is credited with being the first to produce and detect such waves at radio frequencies Nikola Tesla first demonstrated the feasibility of wireless communications Guglielmo Marconi developed commercial workable radio communication Tag. Master Training Module T 1, Page 8

History of RFID - Part 2 1935 1940 1945 1948 1973 Robert Watson Watt got a British patent for radar The first IFF (Identification Friend or Foe) system was developed in Germany Léon Theremin invented “The Thing”, a passive listening device used by the Soviet Union to spy on the American embassy Harry Stockman presented a paper titled "Communication by Means of Reflected Power Mario Cardullo got a US patent for a passive transponder; the first true ancestor of modern RFID Radar/IFF Replica of “The Thing” Cardullo’s patent Stockman’s Triple Turret Reflector Tag. Master AB Tag. Master Training Module T 1, Page 9

RFID System Properties § § § Tag. Master AB The main components of an RFID system are readers and tags (sometimes called interrogators and transponers) The reader is connected to an external system. The external system may be a PC but can also be a simple garage door opener. RFID systems can be classified in a number of ways: frequency, power source, air protocol, etc. Tag. Master Training Module T 1, Page 10

Antenna Detuning § § § A tag antenna is tuned to receive radio waves of a particular frequency When a tag is placed on an object the antenna may be detuned Objects containing metal and/or water can be problematic All tags do not work on all materials, but… … it is possible to design tags that work on e. g. metal or close to water A tag that should not be mounted on metal Tag. Master AB A tag that can be mounted on metal Tag. Master Training Module T 1, Page 12

Antenna Detuning - Example § § The graphs on this page show the reader output power ( 0 d. Bm) 3 required to read an EPC Gen 2 tag at different frequencies (860 60 MHz) 9 The tag is the same in both graphs § § Tag. Master AB Optimized for EU frequencies (865. 6 67. 6 MHz) 8 Optimized for metal mounting In one of the graphs the tag is mounted on metal, in the other the tag is in free air. Exercise: In which graph is the tag mounted on metal? Tag. Master Training Module T 1, Page 13

Power Units § Output power for RFID readers are expressed in different ways § ERP (Effective Radiated Power) § § EIRP (Equivalent Isotropically Radiated Power) § § relative to a dipole antenna (the simplest real antenna) relative to a theoretical isotropic antenna Power values can be converted § PEIRP = PERP 1. 64 Theoretical isotropic antenna Tag. Master AB Dipole antenna Tag. Master Training Module T 1, Page 14

Read and Write Ranges § § Read and write ranges depend on both the reader and the tag. Main parameters 1. 2. 3. Reader output power and frequency ID tag antenna characteristics (and output power for active systems) Reader receiver sensitivity 1 3 2 Tag. Master's 2. 45 GHz Semi-passive System Tag. Master AB Tag. Master Training Module T 1, Page 15

Communication Lobe § Tag. Master AB The communication lobe is the area (in free space) where the tag can be read. It is dependent of both reader and tag. Tag. Master Training Module T 1, Page 16

Communication Lobe Example § Tag. Master AB Example of communication lobe on a site (marked directly on asphalt) Tag. Master Training Module T 1, Page 17

Reading Probability § Reading probability drops from 100% to 0% at the lobe edge Reading probability Perfect read Practical read 100 % Seldom/No read 0 Tag. Master AB 1. 5 3 4. 5 6 7. 5 Distance [m] Tag. Master Training Module T 1, Page 18

Reading Probability § Tag. Master AB An actual measurement of the reading probability Tag. Master Training Module T 1, Page 19

Passing Speed § § Tag. Master AB In high speed applications, the maximum passing speed is obtained by maximizing the time the tag is readable by the reader. A fast train with tags mounted on the side should pass the reader such that the tags pass through the widest part of the lobe. Tag. Master Training Module T 1, Page 20

Passing Speed § Tag. Master AB Tag. Master systems support passing speeds of several hundred km/h. Tag. Master Training Module T 1, Page 21

Passing Speed § Tag. Master AB In some cases (e. g. if a vehicle has a front mounted tag) the time in the lobe can be maximized like this. Tag. Master Training Module T 1, Page 22

Radio Waves § § Tag. Master AB Radio waves are electromagnetic waves with many similarities to light (and some important differences). Electromagnetic waves are self propagating with electric and magnetic components oscillating in phase perpendicular to each other and perpendicular to the direction of energy propagation. Tag. Master Training Module T 1, Page 23

Frequency Spectrum = Gamma rays HX = Hard X rays SX = Soft X rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultrahigh frequency VHF = Very high frequency Radio HF = High frequency waves MF = Medium frequency LF = Low frequency VLF = Very low frequency VF = Voice frequency ELF = Extremely low frequency Tag. Master AB Tag. Master Training Module T 1, Page 24

Superposition Principle § Tag. Master AB When two or more waves traverse the same space, the net amplitude at each point is the sum of the amplitudes of the individual waves. Tag. Master Training Module T 1, Page 25

Interference § Frequency bands used for RFID are also used by other systems § § Tag. Master AB 2. 45 GHz WLAN, Bluetooth, microwave ovens 865 868 MHz (EU) Cordless phones (CT 2) 902 928 MHz (US) Cordless phones, intercoms, radio modems These systems may interfere with the RFID system Tag. Master Training Module T 1, Page 26

Reflection/Absorption/Attenuation § § When an electromagnetic wave hits an object, part of it is reflected, part of it is absorbed and part of it continues attenuated Light and radio waves behave differently § § § Metal mainly reflects radio waves § § It is not possible to read through water (humans are 60% water) Absorption is higher for higer frequencies Glass attenuates radio waves § Tag. Master AB It is not possible to read through metal The reflected wave may interfere with non reflected waves Water mainly absorbs radio waves § § Cardboard blocks light but is transparent to radio waves Water is transparent to light but blocks radio waves The read range of a tag may be reduced if it is placed behind a windscreen Tag. Master Training Module T 1, Page 27

Water Absorption 106 105 Absorption Coefficient (cm-1) 104 103 102 101 100 10 -1 10 -2 10 -3 10 -4 10 -5 102 104 106 108 1010 1012 1014 1016 1018 1020 1022 Frequency (Hz) Image based on data from "Classical Electrodynamics", J. D. Jackson Tag. Master AB Tag. Master Training Module T 1, Page 28

Positive and Negative Identification § Positive identification the user wants to be identified § Negative identification the user does not want to be identified § RFID works well in the positive case § In the negative case it is often possible to hide the tag § § Tag. Master AB Cover the tag with your hand Put the tagged object in a metal bag Tag. Master Training Module T 1, Page 29

Multipath Propagation § § Tag. Master AB Radio waves that reach a tag by different paths interfere. In some spots the waves will cancel out each other. The locations of these dead spots are frequency dependent. Frequency hopping can be used to move the spots around. Compared to a passive tag, a semi passive tag is less sensitive to dead spots as it does not use the RF energy to power the internal electronics. Tag. Master Training Module T 1, Page 30

Frequency Hopping (FHSS) § § When Frequency Hopping is enabled, the reader changes its frequency at short intervals Frequency Hopping eliminates most problems § § Problems caused by reflections Problems caused by interference from other systems (WLAN, etc. ) Frequency Hopping is most efficient in wide frequency bands. Frequency Hopping is enabled by default! No FHSS Tag. Master AB FHSS Tag. Master Training Module T 1, Page 31

Polarization § § § Tag. Master AB Radio waves are polarized RFID tag antennas are linearly polarized. For optimal performance the tag must be rotated in the same way as the electrical field. Tag. Master’s RFID readers use circular polarization to make it possible to read tags with any rotation. Tag. Master Training Module T 1, Page 32

Polarization and Ground Reflections § § § Light reflected from a horizontal surface such as water is horizontally polarized. Polarized sun glasses block horizontally polarized light to reduce the glare. Radio waves behave in the same way A horizontal tag is more sensitive to ground reflections. § § § Multipath interference may create holes and islands in the lobe. The maximum read range may be longer with a horizontal tag. A vertical tag gives a more well defined lobe. Lobe with horizontal tag Tag. Master AB Lobe with vertical tag Tag. Master Training Module T 1, Page 33

End VAC Tag. Master AB Tag. Master Training Module T 1, Page 39