The RFID Tag and Reader

To give all of you a hint into how does RFID works. We won’t be going into too many details of how these things make EM waves and how the reader reads or actuates a passive reader. This is just to give you a know how of what is a RFID tag and Reader.

An RFID tag comprises a microchip mounted on a flexible PET substrate with an attached antenna. This assembly is then sandwiched between a label and its adhesive backing. The RFID tag can become the most widely used application of nanotechnology, as one appreciate the fact that the chip used in these tags are no bigger than grain of sand of the order .3mm² . Although the chips are small what gives these tags their size, is the antenna. The antenna needs to pick up and amplify a signal. As we will eventually be discussing in further posts the uses of RFID tags, one basic fact can be appreciated at this moment is, these tags are meant to facilitate the process of communication between various objects, so these tags are required to send signal strong enough to allow them to be read at distance 3 meters and beyond through materials like boxes, metals, human intervention. After the antenna is attached and the assembly is packaged in a protective laminate, the resulting RFID tag becomes finger size or larger.

RFID tags can be of two types

1.  An active RFID tag
2.  An inactive RFID tag

Active RFID tag broadcasts under their own power. An on board battery powers the microchip circuitry and the transmitter. Active tags are capable of receiving and transmitting signals the distance of a football field. They are suited for applications where they can be permanently mounted. Passive tags have no battery, instead they draw power from the reader. The electromagnetic waves transmitted from the reader induce a current in the tag’s antenna. This energy is used to talk-back to the reader. This is similar to the radar function.

Passive tags are cheaper and suit the function of inventory control and supply chain management, as they tread back information whenever needed, for the rest of time we need them to be just passive.

TAG TYPE	ADVANTAGES	DISADVANTAGES	APPLICATION
ACTIVE	Greater read range, memory capacity, continuous signal	Batteries required	Used with high value asset tracking
SEMI PASSIVE	Greater read range, longer battery life	Battery wear and expense	Reusable containers and asset tracking
PASSIVE READ/WRITE	Longer life, multiple form factors, erasable and programmable	Shorter range than active	Case and pallet applications.
PASSIVE WORM	Suited for item identification, controllable at the packaging source	Limited to a few re-writes, replacing existing data with new data	Case and pallet application
PASSIVE READ ONLY	Simplest approach	Identification only, no tracking updates. Difficult to generate on demand and integrate data	Case and pallet application

THE RFID READERS.

A reader uses an antenna to send signal encoded in either of the form.

i)                    Amplitude modulated waveform

ii)                  Pulse modulated waveform

Readers are available as hand held devices, mobile mounted, fixed read only, and combination reader/encoder. Task of a reader is to communicate with the tag and thus acquire and maintain this information for the task intended, now because many tags may be in presence of a reader, they must be able to receive and manage many replies at once. A reader can tell some tags to wake up and some to sleep, just to manage the communication. 

The above mentioned tags and readers describe the majority chunk of tags and readers that are used in RFID labeling. there are many other variations and differences in the functionality and usage of these tags and readers that come into picture as the usage becomes varied and customized.