VAC TagMaster Training Module T1, Page 1 TagMaster AB TagMaster Training 2013 RFID Theory

TagMaster AB TagMaster Training Module T1, Page 2 Contents Definition of RFID Different types of RFID History of RFID RFID System Radio Waves Radio Regulations Safety and Health

TagMaster AB TagMaster Training Module T1, Page 3 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)

TagMaster AB TagMaster Training Module T1, Page 4 Classification of RFID Systems Frequency 125/134 kHz MHz MHz 2.4 GHz GHz Tag Power Source Passive Semi-passive Active Tag-Reader Protocol Requirements Standard or Proprietary

TagMaster AB TagMaster Training Module T1, Page 5 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. TagMaster provides systems for MHz and 2.45 GHz. LFMFHFVHFUHF 30 kHz300 kHz3 MHz30 MHz300 MHz3 GHz SHF 30 GHz MHz kHz MHz 2.45 GHz 5.8 GHz

TagMaster AB TagMaster Training Module T1, Page 6 Passive, Semi-Passive, and Active Tags Passive Semi-Passive Active No transmitter (backscattering) No battery (powered from RF field) No transmitter (backscattering) Battery to power logic 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, lifetime predictability & read range?

TagMaster AB TagMaster Training Module T1, Page 7 Tag-Reader Protocols The protocol defines how the reader and the tag communicates Compromise of different requirements 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 or Proprietary 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.

TagMaster AB TagMaster Training Module T1, Page 8 History of RFID - Part 1 (History of Radio) 1865James Clerk Maxwell theoretically predicted the existence of electromagnetic waves 1888Heinrich Hertz is credited with being the first to produce and detect such waves at radio frequencies 1893Nikola Tesla first demonstrated the feasibility of wireless communications 1895Guglielmo Marconi developed commercial workable radio communication

TagMaster AB TagMaster Training Module T1, Page 9 History of RFID - Part Robert Watson-Watt got a British patent for radar 1940The first IFF (Identification Friend or Foe) system was developed in Germany 1945 Léon Theremin invented The Thing, a passive listening device used by the Soviet Union to spy on the American embassy 1948 Harry Stockman presented a paper titled "Communication by Means of Reflected Power 1973Mario Cardullo got a US patent for a passive transponder; the first true ancestor of modern RFID Radar/IFF Replica of The Thing Stockmans Triple Turret Reflector Cardullos patent

TagMaster AB TagMaster Training Module T1, Page 10 RFID System Properties 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.

TagMaster AB TagMaster Training Module T1, Page 11 Antennas Both readers and tags contain antennas Different types of antennas are used Patch antennas Dipole antennas Antennas have different radiation patterns Dipole antenna and radiation pattern Patch antenna and radiation pattern

TagMaster AB TagMaster Training Module T1, Page 12 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 metalA tag that can be mounted on metal

TagMaster AB TagMaster Training Module T1, Page 13 Antenna Detuning - Example The graphs on this page show the reader output power (­30 dBm) required to read an EPC Gen 2 tag at different frequencies (860­-960 MHz) The tag is the same in both graphs Optimized for EU frequencies (865.6­ MHz) 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?

TagMaster AB TagMaster Training Module T1, Page 14 Power Units Output power for RFID readers are expressed in different ways ERP (Effective Radiated Power) relative to a dipole antenna (the simplest real antenna) EIRP (Equivalent Isotropically Radiated Power) relative to a theoretical isotropic antenna Power values can be converted P EIRP = P ERP 1.64 Theoretical isotropic antennaDipole antenna

TagMaster AB TagMaster Training Module T1, Page 15 Read and Write Ranges Read and write ranges depend on both the reader and the tag. Main parameters 1. Reader output power and frequency 2. ID-tag antenna characteristics (and output power for active systems) 3. Reader receiver sensitivity TagMaster's 2.45 GHz Semi-passive System

TagMaster AB TagMaster Training Module T1, Page 16 Communication Lobe The communication lobe is the area (in free space) where the tag can be read. It is dependent of both reader and tag.

TagMaster AB TagMaster Training Module T1, Page 17 Communication Lobe Example Example of communication lobe on a site (marked directly on asphalt)

TagMaster AB TagMaster Training Module T1, Page 18 Reading Probability Reading probability Distance [m] 100 % Perfect read Practical read Seldom/No read 0 Reading probability drops from 100% to 0% at the lobe edge

TagMaster AB TagMaster Training Module T1, Page 19 Reading Probability An actual measurement of the reading probability

TagMaster AB TagMaster Training Module T1, Page 20 Passing Speed 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.

TagMaster AB TagMaster Training Module T1, Page 21 Passing Speed TagMaster systems support passing speeds of several hundred km/h.

TagMaster AB TagMaster Training Module T1, Page 22 Passing Speed In some cases (e.g. if a vehicle has a front-mounted tag) the time in the lobe can be maximized like this.

TagMaster AB TagMaster Training Module T1, Page 23 Radio Waves 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.

TagMaster AB TagMaster Training Module T1, Page 24 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 HF = High frequency MF = Medium frequency LF = Low frequency VLF = Very low frequency VF = Voice frequency ELF = Extremely low frequency Radio waves

TagMaster AB TagMaster Training Module T1, Page 25 Superposition Principle 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.

TagMaster AB TagMaster Training Module T1, Page 26 Interference Frequency bands used for RFID are also used by other systems 2.45 GHz WLAN, Bluetooth, microwave ovens MHz (EU)Cordless phones (CT2) MHz (US)Cordless phones, intercoms, radio modems These systems may interfere with the RFID system

TagMaster AB TagMaster Training Module T1, Page 27 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 Cardboard blocks light but is transparent to radio waves Water is transparent to light but blocks radio waves Metal mainly reflects radio waves It is not possible to read through metal The reflected wave may interfere with non-reflected waves Water mainly absorbs radio waves It is not possible to read through water (humans are 60% water) Absorption is higher for higer frequencies Glass attenuates radio waves The read range of a tag may be reduced if it is placed behind a windscreen

TagMaster AB TagMaster Training Module T1, Page 28 Water Absorption Image based on data from "Classical Electrodynamics", J. D. Jackson Frequency (Hz) Absorption Coefficient (cm -1 )

TagMaster AB TagMaster Training Module T1, Page 29 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 Cover the tag with your hand Put the tagged object in a metal bag

TagMaster AB TagMaster Training Module T1, Page 30 Multipath Propagation 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.

TagMaster AB TagMaster Training Module T1, Page 31 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 FHSSFHSS

TagMaster AB TagMaster Training Module T1, Page 32 Polarization 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. TagMasters RFID readers use circular polarization to make it possible to read tags with any rotation.

TagMaster AB TagMaster Training Module T1, Page 33 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. Polarization and Ground Reflections Lobe with vertical tagLobe with horizontal tag

TagMaster AB TagMaster Training Module T1, Page 34 Frequency Regulations In 1897, Guglielmo Marconi founded The Marconi Company to commercially exploit wireless telegraphy. He signed a contract with Llyods insurance company and provided equipment and operators to the insured ships and all major seaports around the world. When competitors started to appear, Marconi decided to exclude them from his network by not allowing them to communicate with his operators. In 1902, Prince Henry, brother of the German Kaiser, was returning from the US on a ship with non-Marconi equipment. Prince Henry wanted to send wireless messages to both Germany and the US but the Marconi operators refused to communicate with him. The Germans realized that the Marconi Company might end up with a monopoly and the military implications of this worried them. The Kaiser invited the UK, France, Spain, Austria, Russia, Italy and the US to the first Berlin International Wireless Conference in 1903 to discuss regulations.

TagMaster AB TagMaster Training Module T1, Page 35 Frequency Regulations At the second Berlin International Wireless Conference in 1906 it was proposed that the ether be divided into regions by wave-lengths and the participants agreed to form the International Radiotelegraph Union. European nations started regulating radio soon after the conferences The US allowed unregulated use of radio frequencies until 1912 after the sinking of the Titanic. The lack of regulations contributed to the severity of the disaster when ships as close as 50 km could not hear the calls for help. Today, radio regulations are coordinated worldwide by the International Telecommunication Union (ITU), which is an agency of the United Nations.

TagMaster AB TagMaster Training Module T1, Page 36 Frequency Regulations in the US Frequency regulations in the US have been handled by the Federal Communications Commission (FCC) since Radio frequency devices are contained in the US Code of Federal regulations, Title 47, Part 15. The document is freely available at

TagMaster AB TagMaster Training Module T1, Page 37 Frequency Regulations in Europe National regulatory bodies, such as Post- och telestyrelsen (PTS) in Sweden, decide about frequency usage in their respective country. The European Conference of Postal and Telecommunications Administrations, CEPT, works to coordinate spectrum usage within Europe and to promote European interests in international negotiations. All standardisation work is done by the European Telecommunications Standards Institute, ETSI, which was created by CEPT in Their recommendations must generally be followed by all EU nations. The following standards are applicable to TagMasters products: ETSI EN , Radio equipment to be used in the 1 GHz to 40 GHz frequency range ETSI EN , Radio Frequency Identification Equipment operating in the band 865 MHz to 868 MHz with power levels up to 2 W The documents are freely available at

TagMaster AB TagMaster Training Module T1, Page 38 Safety and Health TagMasters readers have very low output power compared to many other radio devices Readers should be mounted so that a separation distance of at least 20 cm (8 in) from all persons is provided (Council Recommendation 1999/519/EC) A mobile phone can have 200 times the field strength of a reader TagMasters tags do not have any active transmitting elements The products have certificate for EN :2001 and EN :2001 regarding Exposure to Electro Magnetic Fields Electrical Safety and EN Health 1999/519/EC

VAC TagMaster Training Module T1, Page 39 TagMaster AB End