The birth of RFID systems can be traced back to the 1940s, when the US government used transponders to differentiate friendly aircraft from enemy aircraft. Any basic RFID system consists of three components - an antenna or coil, a transceiver (with decoder) and a transponder (RF tag)- electronically programmed with unique information. The antenna emits radio signals to activate the tag and read and write data to it. Antennas act as conduits between the tag and the transceiver, which controls the system’s data gathering and communication. When an RFID tag is passed through an electromagnetic zone, it detects the reader’s activation signal and the reader decodes the data in the tag’s silicon chip and the data is passed to the host computer for processing.

RFID tags come in a variety of shapes and sizes like animal tracking tags that can be inserted beneath the skin to credit card shaped tags for use in access applications like lanyards. As a result, RFIDs are used in a wide variety of applications in areas like transportation, logistics, manufacturing, security etc.

RFIDs can also be broadly classified into two categories–active and passive tags. While both use radio frequency energy to communicate between a tag and a reader, the method of powering the tags is different. Active RFID uses an internal power source (battery) in the tag to continuously power the tag and its RF communication circuitry, whereas Passive RFID relies on RF energy transferred from the reader to the tag to power the tag.

RFIDs can also be calssified on the range of frequency they use - high frequency (850-950 MHz and 2.4-5 GHz), intermediate frequency (10-15 MHz) and low frequency (100-500kHz). Low-frequency tags are used for applications such as security access that need shorter ranges. High-frequency systems are used for applications such as toll-collection that need longer ranges.