What is RFID?

  Knowledge Center

Radio frequency identification, or RFID, is a generic term for technologies that use radio waves to automatically identify objects. There are several methods of identification, but the most common is to store a serial number that identifies the object and perhaps other information, on a microchip that is attached to an antenna (the chip and the antenna together are called an RFID transponder or an RFID tag). The antenna enables the chip to transmit the identification information to a reader. The reader converts the radio waves emitted by the RFID tag into digital information that can then be passed on to computers that can make use of it.

What are the Major Components of an RFID System?

Deploying a radio frequency identification system that delivers true business value involves much more than purchasing the right tags and installing the right readers. To get business value from the all of the information collected, companies also need middleware to filter the collected raw tag data.

Tags and Readers

Tags and readers are the main components of an RFID system. There are two basic types of tags, active and passive. Active RFID tags have a transmitter and their own power source (typically a battery). The power source is used to run the microchip’s circuitry and to broadcast a signal to a reader (the way a cell phone transmits signals to a base station). Passive tags have no battery. Instead, they draw power from the reader, which sends out electromagnetic waves that induce a current in the tag’s antenna. Semi-passive tags use a battery to run the chip’s circuitry, but communicate by reflecting power from the reader.

Readers can house internal or external antennas. Readers with external antennas can have one or more ports for connecting additional antennas. Readers can also have input/output ports for connecting to external devices. An input port might be connected to an electric eye that activates the reader when something passes through its field of view. An output port might connect to a programmable logic controller, conveyor sorter or other device controlled by the reader. Readers also have ports for connecting to a computer or network.


Middleware is a generic term used to describe software that resides between the RFID reader and enterprise applications. The middleware takes raw data from the reader (which might read the same tag 100 times per second), filters it and passes on the useful event data to back-end systems. Middleware can play a key role in getting the right information to the right application at the right time.

What are Active RFID Systems?

Active tags may be broadly operated in one of two operational modes: as transponders and/or as beacons. Active transponders are awakened when they receive a signal from a reader. Popular applications are in toll payment collection, checkpoint control and other choke-point systems. For example when a car with an active transponder approaches a tollbooth, a reader at the booth sends out a signal that activates the transponder on the car windshield. The transponder then transmits its unique ID to the reader. In this manner, transponders conserve battery life by enabling the tag to send a signal only when it is within range of a reader.

Active beacons are utilized in real-time locating systems (RTLS) that cannot accommodate choke points. A beacon emits a signal with its unique identifier at pre-set intervals, for example, once every second, every minute, every hour, or several times per day, depending on the urgency of the location tracking application.

Active tags can be read reliably because they transmit (rather than reflect) a signal to the reader. Read ranges of 100 meters (greater than 300-feet) is common, but range often depends on the antenna type, environmental factors, and regulatory constraints. Active tags can cost from $10 to a few hundred dollars, depending on their capability, amount of memory, battery life, and integrated sensor functionality.