Why RFID ?

Radio frequency identification (RFID) is one of the most rapidly growing segments of today's automatic identification data collection (AIDC) industry. This systems use radio frequency to identify, locate and track people, assets, and animals. Beckoning benefits are offered by RFID system facilitates operations in the supply chain management, tracking of goods and personnel, process automation, access control and anti-counterfeiting.

An RFID-system consists of a transponder (or RFID tag - a microchip with an antenna) which is tagged or placed on an item and then reader (a device with one or more antennas) is used to read data from the microchip using radio waves. The reader passes the information to a computer, so that the data can be used to create business value. RFID tags can both read or written using a reader.

Industry experts consider RFID as an advantageous complement to bar code technology in many cases, such as tracking pallets, cartons and cases in a warehouse, where both technologies are used. The advanced RFID technology, in fact, overcomes certain limitations of bar code applications. As RFID is not an optical technology like bar coding, no inherent line of sight is required between the reader and the tagged RFID object. Furthermore, RFID transmits data wirelessly and is a "read-write" technology, so it can update or change the data encoded in the tag during the tracking cycle.

Categories of RFID
Depending on the source of electrical power RFID tags are categorized into two; Passive & Active.

Passive RFID
Passive tags beget power from the signal of an external reader. As shown in the Figure above, the passive RFID tag gets power from the RF field (magnetic field) generated by the reader antenna. If the magnetic field generated by the reader antenna is strong enough then a current is induced in the tag antenna, which in-turn activates the memory chip. On activation, the chip's unique identification number and other data stored in the chip is transmitted by the tag in response to different commands from the reader.

The advantage of Passive tags is that it can operate at low frequency, high frequency and ultra-high frequency. Low-frequency systems generally operate at 124 kHz, 125 kHz or 135 kHz. Whereas high-frequency systems use 13.56 MHz, and ultra-high frequency systems use a band anywhere from 860 MHz to 960 MHz. Some systems also use 2.45 Ghz and other areas of the radio spectrum. Radio waves behave differently at each of these frequencies, which means the different frequencies are suitable for different applications.

In addition to the above advantage some more highlights of passive RFID tags are:

• The tag is much smaller. These tags have almost unlimited applications in consumer goods and other areas.
• The tag functions without a battery; these tags have a useful life of twenty years or more.
• The tag is typically much less expensive therefore useful in item level tagging.

The read range of passive RFID varies from few centimeters to few meters depending upon the tag size, reader antenna size, power emitted by the reader, operating frequency and environmental conditions.

Active RFID
The active RFID tags contain their own power source, usually as an on-board battery. Active tags are used on large assets, such as cargo containers, rail cars and large reusable containers, etc., which need to be tracked over long distances (in a distribution yard, for example). They usually operate at 455 MHz, 2.45 GHz, or 5.8 Ghz, and they typically have a read range of 60 feet to 300 feet (20 meters to 100 meters).

Active RFID tags have a read range of up to 300 feet (100 meters) and can be reliably read because they broadcast a signal to the reader (some systems can be affected by rain). They generally cost from $10 to $50, depending on the amount of memory, the battery life required, whether the tag includes an on-board temperature sensor or other sensors and the ruggedness required. A thicker, more durable plastic housing will increase the cost.