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The Basics of RFID Technology

There are many different types of radio frequency identification technology. This article explains the difference between active and passive tags and between low-, high- and ultra-high frequency systems.
By Bob Violino
Jan 16, 2005Radio frequency identification is the next wave in the evolution of computing. Essentially, it's a technology that connects objects to Internet, so they can be tracked, and companies can share data about them. The concept is simple: Place a transponder—a microchip with an antenna—on an item and then use a reader—a device with one or more antennas—to read data off of the microchip using radio waves. The reader passes the information to a computer, so that the data can be used to create business value.

There are many different types of RFID systems, and installing them and using them to generate data that can be used to cut costs or boost efficiency is challenging. It's important to choose the right type of RFID system for a particular application. It's also important to work with an experienced systems integrator to make sure the system is installed and configured properly.

The purpose of this article is to introduce you to the basics of RFID technology. We present a lot of technical information. It's not critical that you grasp it all. Understanding the major differences between the various types of systems will help you choose the right systems integrator and work with the integrator to choose the right RFID technology for your needs.

Active tags can broadcast a signal over long distances
The vast majority of RFID tags or transponders (the tags are often used interchangeably) use a silicon microchip to store a unique serial number and usually some additional information (for information on systems that don't use microchips, see our FAQs). There are two broad categories of RFID systems—passive and active systems. Passive RFID tags do not have a transmitter; they simply reflect back energy (radio waves) coming from the reader antenna. Active tags have their own transmitter and a power source, usually—but not always—a battery (active tags could draw energy from the sun or other sources). They broadcast a signal to transmit the information stored on the microchip. (There are also semi-passive and battery-assisted RFID tags, which are suitable for specific applications. These are covered in our FAQs and Glossary.)

Active RFID Systems
Active tags are used on large assets, such as cargo containers, rail cars and large reusable containers, 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).

Broadly speaking, there are two types of active tags: transponders and beacons. Active transponders are woken up when they receive a signal from a reader. These are used in toll payment collection, checkpoint control and other systems. When a car with an active transponder approaches a tollbooth, a reader at the booth sends out a signal that wakes up the transponder on the car windshield. The transponder then broadcasts its unique ID to the reader. Transponders conserve battery life by having the tag broadcast its signal only when it is within range of a reader.

Beacons are used in most real-time locating systems (RTLS), where the precise location of an asset needs to be tracked. In an RTLS, a beacon emits a signal with its unique identifier at pre-set intervals (it could be every three seconds or once a day, depending on how important it is to know the location of an asset at a particular moment in time). The beacon's signal is picked up by at least three reader antennas positioned around the perimeter of the area where assets are being tracked. RTLS are usually used outside, say, in a distribution yard (see Logistics Gets Cheaper by the Yard), but automakers use the systems in large manufacturing facilities to track parts bins (see RFID Revs Up Hummer Plant).

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