UHF RFID TAGS

RFID (Radio Frequency Identification) is a technology used for electronic and wireless identification of objects, humans and animals


RFID System



Carrier Frequencies


Refers to the property of radio waves used to transmit data


RFID systems may use a particular frequency band depending on:


  • Application

  • Legislature

  • Cost considerations


Frequency and bandwidth


  • Frequency is of primary importance when determining data transfer rates (bandwidth)

  • The higher the frequency, the higher the data transfer rate

Range and Power


  • The range that can be achieved in an RFID system is determined by

  • The power available at the reader

  • The power available within the tag

  • The environmental conditions and structures


Material Propagation


  • The absorption rate for water and other non- conductive substances is lower by a factor of 100 000 at 100 kHz than it is at 1 GHz

  • LF systems are primarily used due to their high propagation of substances


Electromagnetic Interference


  • Electromagnetic Interference - Interference caused when the radio waves of one device distort the waves of another.

  • Cells phones, wireless computers and even robots in factories

  • can produce radio waves that interfere with RFID tags.

  • EI is likely to be an issue for UHF systems


Tags Characteristics


• Means by which transponder is powered

• Data carrying options

• Data read rates

• Programming options

• Physical forms

• Costs


Active and Passive


• Active tags


◦ Powered by an internal battery

◦ Finite lifetime (because of battery)

◦ Greater range

◦ Better noise immunity

◦ Higher data transmission rates


• Passive tags


◦ Operate without battery

◦ Derive power from the field generate by the reader

◦ Less expensive

◦ Unlimited life

◦ Require more powerful readers

◦ Orientation sensitivity


Data Carrying


◦ An identifier

▪ 1bit – 128 bits


◦ Portable data files

▪ Example: 64 K


Data Programming


• Read-only

◦ Cheap


• Write once read many


• Read/write

◦ Expensive


Inventory tracking


• RFID tag data capacity is big enough that any tag will have a unique code, while current bar codes are limited to a single type code for all instances of a particular product.


• The uniqueness of RFID tags means that a product may be individually tracked as it moves from location to location, finally ending up in the consumer's hands. This may help companies to combat theft and other forms of product loss.

• the visibility provided by RFID allows an accurate knowledge on the inventory level by eliminating the discrepancy between inventory record and physical inventory.


◦ In an academic study performed at Wal-Mart, RFID reduced Out of Stocks by 30 percent for products selling between 0.1 and 15 units a day.


• It has also been proposed to use RFID for POS store checkout to replace the cashier with an automatic system which needs no barcode scanning. However, this is not likely to be possible without a significant reduction in the cost of current tags


Some Application

  • Warehouse Management

  • Asset Management

  • library tracking

  • transportation payments

  • pallet tracking

  • airline baggage tracking

  • apparel and pharmaceutical items tracking

  • identification badges

  • shipping container tracking, and truck and trailer tracking in shipping yards


RFID


• Several market research firms predict that

~2007 RFID market will reach ~$3 billion


• The lowest cost of Gen2 EPC inlay is offered by SmartCode at a price of 5 cents apiece in volumes of 100 million or more


Standards


• The manufacturer, distributor and retailer must all have systems that are compatible with one another.


• This doesn’t just apply to back-end systems, but to the tags themselves if RFID is to be effective.


• Some of the early compatibility issues were very fundamental — such as the frequency the tags operate on.


• For the most part, the 869 to 915 MHz tags prevailed, but still left the hurdle of the actual tag content.


• It became obvious that tag formats, just like barcode formats, needed standardization.


• This was addressed through the Electronic Product Codes (EPCglobal), an industry body that sets these electronic standards.


• However, having the frequency and tag format agree only buys so much if the air protocol to get the data isn’t established.


• Until recently it was difficult to guarantee that a reader from one manufacturer would work with a tag from another, until the EPC Generation 2 air specification.


• Now, both tag and reader vendors all signed up to make their equipment compatible


• All manufacturers has cross compatible offerings


• While the EPC now has a standard adopted by the vendors in the US and Europe, there continue to be difficulties with international compatibility. Almost all of the participants in EPC are from the U.S. and Europe, while a significant portion of manufactured goods are no longer made in those member countries.


• As respected as EPC may be, it would require a higher authority to mandate a world- wide standard.


• That’s where the International Standards Organization (ISO) comes in.


• The EPC Generation 2 specification was submitted to ISO and just recently it became an approved standard with the designation ISO/IEC 18000 to 6C.


• With ISO approval, it’s now possible to buy a compliant Reader and tag that works the world over.


Regulations


• Europe faces significant problems with reader performance degradation in environments where high numbers of readers are used together.


• This performance degradation issue originates from the fact that the EU has a more limited range of spectrum that’s legally assigned for RFID use compared to the USA.



• In North America, UHF can be used unlicensed for 902 – 928 MHz (±13 MHz from the 915 MHz center frequency), but restrictions exist for transmission power.


• In Europe, RFID and other low-power radio applications are regulated by ETSI recommendations EN 300 220 and EN 302 208, and ERO recommendation 70 03, allowing RFID operation with somewhat complex band restrictions from 865–868 MHz.


• Readers are required to monitor a channel before transmitting ("Listen Before Talk"); this requirement has led to some restrictions on performance, the resolution of which is a subject of current research.


• The North American UHF standard is not accepted in France as it interferes with its military bands.


• For China and Japan, there is no regulation for the use of UHF. Each application for UHF in these countries needs a site license, which needs to be applied for at the local authorities, and can be revoked.


• For Australia and New Zealand, 918 – 926 MHz are unlicensed, but restrictions exist for transmission power.


Privacy


• Since the owner of an item will not necessarily be aware of the presence of a RFID tag and the tag can be read at a distance without the knowledge of the individual, it becomes possible to gather sensitive data about an individual without consent. (Ex. Scanning your home, medical records)


• A number of products are available on the market in the US that will allow a concerned carrier of RFID-enabled cards to shield their data


• Shielding is again a function of the frequency being used.


◦ Low-frequency tags, like those used in implantable devices for humans and pets, are relatively resistant to shielding, though thick metal foil will prevent most reads.


◦ High frequency tags (13.56 MHz — smart cards and access badges) are more sensitive to shielding and are difficult to read when within a few centimeters of a metal surface.


Tag Sample










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