Introduction to RFID

 Stands for (Radio Frequency Identification Device)
 (RFID) is the wireless use of electromagnetic fields to transfer data, for the
purposes of automatically identifying and tracking tags attached to objects.
 The tags contain electronically stored information. Some tags are powered by
electromagnetic induction from magnetic fields produced near the reader.
 Electromagnetic induction is the production of an electromotive force across a
conductor when it is exposed to a varying magnetic field.

 Some types collect energy from the interrogating radio waves and act as a passive
transponder. Other types have a local power source such as a battery and may
operate at hundreds of meters from the reader.
 RFID is one method for Automatic Identification and Data Capture (AIDC)
 In 1945, Léon Theremin invented an espionage tool for the Soviet Union which
retransmitted incident radio waves with audio information.

 RFID tags can be either passive, active or battery-assisted passive. An active tag has
an on-board battery and periodically transmits its ID signal. A battery-assisted
passive (BAP) has a small battery on board and is activated when in the presence of
an RFID reader. A passive tag is cheaper and smaller because it has no battery;
instead, the tag uses the radio energy transmitted by the reader. However, to operate a
passive tag, it must be illuminated with a power level roughly a thousand times
stronger than for signal transmission. That makes a difference in interference and in
exposure to radiation.
 An RFID reader transmits an encoded radio signal to interrogate the tag. The RFID
tag receives the message and then responds with its identification and other
information. This may be only a unique tag serial number, or may be product-related
information such as a stock number, lot or batch number, production date, or other
specific information. Since tags have individual serial numbers, the RFID system
design can discriminate among several tags that might be within the range of the
RFID reader and read them simultaneously

 RFID systems can be classified by the type of tag and reader. A Passive Reader
Active Tag (PRAT) system has a passive reader which only receives radio signals
from active tags (battery operated, transmit only). The reception range of a PRAT
system reader can be adjusted from 1–2,000 feet (0–600 m), allowing flexibility in
applications such as asset protection and supervision.
 An Active Reader Passive Tag (ARPT) system has an active reader, which
transmits interrogator signals and also receives authentication replies from
passive tags.
 An Active Reader Active Tag (ARAT) system uses active tags awoken with an
interrogator signal from the active reader. A variation of this system could also use
a Battery-Assisted Passive (BAP) tag which acts like a passive tag but has a small
battery to power the tag's return reporting signal.

 Public transport
 RFID cards are used for access control to public transport.
 In London travelers use Oyster Cards on the tube, buses and ferries. It identifies the
traveler at each turnstile and so the system can calculate the fare.
 Passports
Biometric passport
 The first RFID passports ("E-passport") were issued by Malaysia in 1998. In addition
to information also contained on the visual data page of the passport, Malaysian e-
passports record the travel history (time, date, and place) of entries and exits from the
country.
 Other countries that insert RFID in passports include Norway (2005), Japan (March 1,
2006), most EU countries (around 2006), Australia, Hong Kong, the United States
(2007), India (June 2008), Serbia (July 2008), Republic of Korea (August 2008),
Taiwan (December 2008), Albania (January 2009), The Philippines (August 2009),
Republic of Macedonia (2010), and Canada (2013).

 In many countries, RFID tags can be used to pay for mass transit fares on bus,
trains, or subways, or to collect tolls on highways.
 Some bike lockers are operated with RFID cards assigned to individual users. A
prepaid card is required to open or enter a facility or locker and is used to track
and charge based on how long the bike is parked.
 The Zipcar car-sharing service uses RFID cards for locking and unlocking cars and
for member identification

 Animal identification
 RFID tags for animals represent one of the oldest uses of RFID. Originally meant
for large ranches and rough terrain, since the outbreak of mad-cow disease, RFID
has become crucial in animal identification management. An implantable RFID
tag or transponder can also be used for animal identification. The transponders
are more well known as passive RFID, or "chips" on animals. The Canadian Cattle
Identification Agency began using RFID tags as a replacement for barcode tags.

 Implantable RFID chips designed for animal tagging are now being used in
humans. An early experiment with RFID implants was conducted by British
professor of cybernetics Kevin Warwick, who implanted a chip in his arm in 1998.
In 2004 Conrad Chase offered implanted chips in his night clubs
in Barcelona and Rotterdam to identify their VIP customers, who in turn use it to
pay for drinks.

 Libraries have used RFID to replace the barcodes on library items. The tag can
contain identifying information or may just be a key into a database. An RFID
system may replace or supplement bar codes and may offer another method of
inventory management and self-service checkout by patrons. It can also act as
a security device, taking the place of the more traditional electromagnetic security
strip.
 It is estimated that over 30 million library items worldwide now contain RFID
tags, including some in the Vatican Library in Rome.

 RFID technologies are now also implemented in end-user applications in
museums. An example was the custom-designed temporary research application,
"eXspot," at the Exploratorium, a science museum in San Francisco, California. A
visitor entering the museum received an RF Tag that could be carried as a card.
The eXspot system enabled the visitor to receive information about specific
exhibits. Aside from the exhibit information, the visitor could take photographs of
themselves at the exhibit. It was also intended to allow the visitor to take data for
later analysis. The collected information could be retrieved at home from a
"personalized" website keyed to the RFID tag.

 School authorities in the Japanese city of Osaka are now chipping children's
clothing, backpacks, and student IDs in a primary school. A school in Don
caster, England is piloting a monitoring system designed to keep tabs on pupils by
tracking radio chips in their uniforms. St Charles Sixth Form College in
west London, England, started September, 2008, is using an RFID card system to
check in and out of the main gate, to both track attendance and prevent
unauthorized entrance. Similarly, Whitcliffe Mount School in Cleckheaton,
England uses RFID to track pupils and staff in and out of the building via a
specially designed card. In the Philippines, some schools already use RFID in IDs
for borrowing books and also gates in those particular schools have RFID ID
scanners for buying items at a school shop and canteen, library and also to sign in
and sign out for student and teacher's attendance.

SPORTS
 RFID for timing races began in the early 1990s with pigeon racing, introduced by
the company Deister Electronics in Germany. RFID can provide race start and end
timings for individuals in large races where it is impossible to get accurate
stopwatch readings for every entrant.

 Telemetry
 Active RFID tags also have the potential to function as low-cost remote sensors
that broadcast telemetry back to a base station. Applications of tagometry data
could include sensing of road conditions by implanted beacons, weather reports,
and noise level monitoring.

 Long checkout lines at the grocery store are one of the biggest complaints about
the shopping experience. Soon, these lines could disappear when the ubiquitous
Universal Product Code (UPC) bar code is replaced by smart labels, also called
radio frequency identification (RFID) tags. RFID tags are intelligent bar codes
that can talk to a networked system to track every product that you put in your
shopping cart.
 Imagine going to the grocery store, filling up your cart and walking right out the
door. No longer will you have to wait as someone rings up each item in your cart
one at a time. Instead, these RFID tags will communicate with an electronic
reader that will detect every item in the cart and ring each up almost instantly.
The reader will be connected to a large network that will send information on your
products to the retailer and product manufacturers.
 Your bank will then be notified and the amount of the bill will be deducted from
your account. No lines, no waiting.

 As with any antenna, and RFID antenna follows the basic rules of any antenna system. The antenna is
basically a form of tuned circuit. Power is fed into the antenna and much of it is radiated. As all passive
antennas are perform in an equivalent manner in reception as they do in transmission, it is often easier to
look at them as a radiating element as it is often easier to look at the concepts in terms of radiation.
 There are a number of parameters and definitions for antennas that are useful when looking at RFID
antennas:
 Radiation resistance: The resistance that equates to that which would be required to dissipate any power
that is radiated.
 Resistive losses: The losses that occur as a result of the resistance of the antenna elements - these losses
plus the radiated power equate to the total input power.
 Bandwidth: The band over which the antenna will operate satisfactorily. Normally antennas operate as
resonant elements and therefore their performance falls either side of the centre frequency. This must be
accounted for in the design of the RFID antenna, or any other antenna for that matter.
 Feed impedance: The current and voltage will vary along the length of the antenna element. Voltage rises
towards the ends and the current falls and is also dependent upon the length of the antenna, etc. As
impedance is the ratio of current and voltage this means that the feed impedance varies. TO ensure the
maximum power transfer the source and load impedances must match, and therefore the feed impedance of
the antenna is particularly important to ensure efficient operation.
 These and many other parameters are used when designing antennas and in this case RFID antennas.


With antennas in many RFID systems being very small when compared to wavelength, the
bandwidth of the antenna tends to be small. This can create problems when used with
modulation systems that may use wider bandwidths.
 Some RFID systems send data at very low data rates and in a straightforward manner - others
use a subcarrier and this increases the bandwidth required. In view of the small size of the
antenna with respect to the wavelength, the bandwidth of the antenna may be sufficiently
narrow that the centre frequency may radiate well, but the sidebands arising from the
subcarrier and modulation may be outside the antenna bandwidth and may not radiate
effectively.
 The RFID antenna bandwidth required can be determined from the following formula:
 Bandwidth = Ftol + Fsc + Max data rate
 Where
Bandwidth is in Hertz
Ftol is the frequency tolerance of the antenna
Fsc is the frequency of the sub carrier in Hertz
Max data rate is expressed in bits per second

 What's the difference between passive and active tags?
 Active RFID tags have a transmitter and their own power source (typically a
battery). The power source is used to run the microchip's circuitry and to
broadcast a signal to a reader (the way a cell phone transmits signals to a base
station). Passive tags have no battery. Instead, they draw power from the reader,
which sends out electromagnetic waves that induce a current in the tag's antenna.
Semi-passive tags use a battery to run the chip's circuitry, but communicate by
drawing power from the reader. Active and semi-passive tags are useful for
tracking high-value goods that need to be scanned over long ranges, such as
railway cars on a track, but they cost more than passive tags, which means they
can't be used on low-cost items.

 How much information can an RFID tag store?
 It depends on the vendor, the application and type of tag, but typically a tag
carries no more than 2 kilobytes (KB) of data—enough to store some basic
information about the item it is on. Simple "license plate" tags contain only a 96-
bit or 128-bit serial number. The simple tags are cheaper to manufacture and are
more useful for applications where the tag will be disposed of with the product
packaging. The aerospace industry wants to store parts histories on high memory
tag, which has led to the introduction of passive UHF tags that store 4KB or 8KB
of data.

 What's the difference between read-only and read-write RFID tags?
 Microchips in RFID tags can be read-write, read-only or “write once, read many”
(WORM). With read-write chips, you can add information to the tag or write over
existing information when the tag is within range of a reader. Read-write tags
usually have a serial number that can't be written over. Additional blocks of data
can be used to store additional information about the items the tag is attached to
(these can usually be locked to prevent overwriting of data). Read-only microchips
have information stored on them during the manufacturing process. The
information on such chips can never be changed. WORM tags can have a serial
number written to them once, and that information cannot be overwritten later.

 There really is no such thing as a "typical" RFID tag, and the read range depends
on whether the tag is active or passive. Active tags broadcast a signal, so they
have a much longer read range—300 feet or more—than passive tags. The read
range of passive tags depends on many factors: the frequency of operation, the
power of the reader, interference from other RF devices and so on. In general, low-
frequency and high-frequency tags tags are read from within three feet (1 meter)
and UHF tags are read from 10 to 20 feet. Readers with phased array antennas
can increase the read range of passive tags to 60 feet or more.

 Tag collision occurs when more than one transponder reflects back a signal at the
same time, confusing the reader. Different air interface protocol standards (and
different proprietary systems) use different techniques for having the tags
respond to the reader one at a time. These involve using algorithms to "singulate"
the tags. Since each tag can be read in milliseconds, it appears that all the tags
are being read simultaneously.

 Most passive RFID tags simply reflect back waves from the reader. Energy
harvesting is a technique in which energy from the reader is gathered by the tag,
stored briefly and transmitted back to the reader.

 "Chip less RFID" is a generic term for systems that use RF energy to communicate
data but don't store a serial number in a silicon microchip in the transponder.
Some chip less tags use plastic or conductive polymers instead of silicon-based
microchips. Other chip less tags use materials that reflect back a portion of the
radio waves beamed at them. A computer takes a snapshot of the waves beamed
back and uses it like a fingerprint to identify the object with the tag. Companies
are experimenting with embedding RF reflecting fibers in paper to prevent
unauthorized photocopying of certain documents. There are inks that reflect back
radio waves at certain frequencies, enabling farmers, for example, to tattoo a chip
less RFID transponder on an animal for identification purposes.

 I've heard that RFID doesn't work around metal and water. Does that mean I
can't use it to track cans or liquid products?
 Low- and high-frequency tags work better on products with water and metal. In
fact, there are applications in which low-frequency RFID tags are embedded in
metal auto parts to track them. Radio waves bounce off metal and are absorbed by
water at ultrahigh frequencies. That makes tracking metal products, or those with
high water content, with passive UHF tags challenging. However, in recent years,
companies have developed special UHF tags designed to overcome these
challenges. There are also ways to tag products with metal or water content to
ensure reliable read rates

 Data is typically stored in user memory on a tag. This is separate from the field
for the unique serial number, which can be pre-programmed or assigned by a user.
The air-interface protocol standards for passive HF and UHF tags (for example,
the UHF EPC Gen 2 standard) define basic operations, including read-write, and
which memory banks or blocks can be written to. Reader manufacturers often
combine these low-level commands with higher-level subroutines in their software
development kits, so they can be used by application developers.

 The debate between RFID and smart cards technology is an ongoing one. There is
no clear definition that describes RFID and smart cards.
 The applications for which RF is used can be different for RFID and smartcards.
RFID is mainly meant for applications within the supply chain, for track and
trace. Contactless smart cards on the other hand are mainly meant for
payments/banking, mass transit, government and ID, and access control. This
article aims at clearing the confusion between the two technology definitions.

 Smart cards offer a number of features that can be used to provide or enhance
privacy protection in systems. The following is a brief description of some of these
features and how they can be used to protect privacy.
 Authentication
 Secure data storage
 Encryption
 Strong device security
 Secure communications
 Biometrics
 Personal device

Introduction to RFID

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