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Tag – You’re It! The Low Down on RFID Tags
RFID Tags Use Different Frequencies
Figuring out Radio Frequency Identification (RFID) can seem like a jungle at times. The building blocks are simple enough: RFID tags, RFID antennas and RFID readers. The tough question, when starting out down the RFID road, is what frequency is right for the application and what combination of RFID tags, RFID readers and RFID antennas is the right combination?
RFID tags are classified by frequencies. RFID tags, antennas and readers are tuned just like a radio is tuned to a specific frequency to receive different stations. RFID has different flavors of a similar technology. For example, low frequency RFID and high frequency RFID tags can be used globally without a license. RFID Tags Are Categorized By Radio Frequency
RFID Frequency Groupings
1. Low Frequency RFID Tags (125 kHz or 134.2kHz)
2. High Frequency RFID Tags (13.56 MHz)
3. UHF RFID Tags (868 MHz to 956 MHz) a.k.a. GEN2 RFID
4. Microwave RFID Tags (2.45 GHz)
Individual countries govern the use of various frequencies differently
Ultra-high-frequency (UHF) RFID tags cannot be used globally as there is no single global standard. Europe uses 868 MHz. for its UHF RFID applications while North America uses 915 MHz.. In North America, UHF can be used for RFID unlicensed for 902 - 928 MHz (+/-13 MHz from the 915 MHz center frequency), but restrictions exist for transmission power. In Europe, RFID is regulated by ETSI recommendations EN 300 220 and EN 302 208, and ERO recommendation 70 03. This allows for RFID Tag operation from 865-868 MHz. The North American UHF standard is not accepted in France as it interferes with its military bands For Australia and New Zealand, 918 - 926 MHz are unlicensed, but restrictions exist for transmission power. The use of 2.45GHz Microwave RFID tags are restricted in Israel, China and Japan.
Different vertical markets require different RFID tags as each frequency range has its advantages and disadvantages. Low Frequency RFID tags (LF) are less costly to manufacturer than Ultra High Frequency (UHF) RFID tags. UHF RFID tags offer better read/write range and can transfer data faster then other RFID tags. HF RIFD tags work best at close range and are highly effective at penetrating non-metal objects especially objects with high water content.
Attention recently has been focused on the supply chain. The initiatives driven by WalMart and the DoD have created a new level of RFID awareness. These initiatives have also accelerated the creation of new RFID GEN 2 standards. GEN 2 is beginning to unseat some legacy RFID practices.
Various Types of RFID Tags
There are two types of RFID tags: active RFID tags and passive RFID tags.
Passive RFID tags have no internal power supply. Instead, a small electric current is created in the antenna when an incoming signal reaches it. This current provides enough power to briefly activate the tag, usually just long enough to relay simple information, such as an ID number or product name. Because passive RFID tags do not contain a power supply, they can be very small in size, sometimes thinner than a piece of paper. Passive RFID tags can be activated from a distance of ten millimeters to over six meters away.
Active RFID tags contain an internal power source, which allows for a longer read-range and for a bigger memory on the tag itself. The power source also makes it possible to store information sent by the transceiver. Active RFID tags are larger than passive tags - usually slightly bigger than a coin. They can be read from many meters away and generally have a battery life of about ten years. Advantages of active tags include accuracy, reliability, and superior performance in adverse RFID environments such as water or metal.
The major advantages of active RFID tags is that it can be read at distances of one hundred feet or more and that it may have other sensors that can use electricity for power. Active RFID tags may have longest communication range of any RFID tag. Active tags can perform independent monitoring and control and initiate communications. These tags can perform diagnostics and be equipped with autonomous networking. The disadvantages of active RFID tags are that the tags cannot function without battery power, which limits the lifetime of the tag. Active RFID tags are more expensive often costing $20 or more per tag. The tag is physically larger, which may limit its use in certain applications. The maintenance costs for an active RFID tag are greater than a passive tag if batteries need to be monitored and replaced. Battery outages in an active RFID tag can result in costly misreads. |
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