RFID stands for radio frequency identification. It is an automatic identification technology whereby digital data encoded in an RFID tag or "smart label" is captured by a reader using radio waves. Put simply, RFID is similar to barcode technology but uses radio waves to capture data from tags, rather than optically scanning the barcodes on a label. RFID does not require the tag or label to be seen to read its stored data—that's one of the key characteristics of an RFID system.
RFID tags consist of an integrated circuit (IC) attached to an antenna—typically a small coil of wires—plus some protective packaging (like a plastic card) as determined by the application requirements. Tags also sometimes are called "transponders," and sometimes they are called "inlays," although technically an inlay is a tag mounted on a substrate that is ready to be converted into a smart label. RFID tags can come in many forms and sizes. Some can be as small as a grain of rice. Data is stored in the IC and transmitted through the antenna to a reader. RFID tags are either "passive" (no battery) or "active" (self-powered by a battery). Tags also can be read-only (stored data can be read but not changed), read/write (stored data can be altered or rewritten), or a combination, in which some data is permanently stored while other memory is left accessible for later encoding and updates.
"Smart labels" go beyond simple tag functionality by combining human-readable information and barcode technology with RFID. A smart label consists of an adhesive label that is embedded with an ultra-thin RFID tag "inlay" (which is a tag—IC plus antenna—mounted on a substrate). Smart labels combine the read range and unattended processing capability of RFID with the convenience and flexibility of on-demand label printing. Smart labels also can be pre-printed and pre-coded for use. In on-demand applications, the tag inlay can be encoded with fixed or variable data and tested before the label is printed, and the label can retain all existing formats and layouts that are required to support barcodes, text, and graphics used in established applications. A read/write smart label also can be programmed and reprogrammed in use, following initial coding during the label production process.
A reader (now more typically referred to as an RFID interrogator) is basically a radio frequency (RF) transmitter and receiver, controlled by a microprocessor or digital signal processor. The reader, using an attached antenna, captures data from tags, then passes the data to a computer for processing. As with tags, readers come in a wide range of sizes and offer different features. Readers can be affixed in a stationary position (for example, beside a conveyor belt in a factory or dock doors in a warehouse), portable (integrated into a mobile computer that also might be used for scanning barcodes), or even embedded in electronic equipment such as print-on-demand label printers.
Information is sent to and read from RFID tags by a reader using radio waves. In passive systems, which are the most common, an RFID reader transmits an energy field that "wakes up" the tag and provides the power for the tag to respond to the reader. In active systems, a battery in the tag is used to boost the effective operating range of the tag and to support additional features over passive tags, such as temperature sensing. Data collected from tags is then passed through communication interfaces (cable or wireless) to host computer systems in the same manner that data scanned from barcode labels is captured and passed to computer systems for interpretation, storage, and action.
Passive smart label RFID systems offer unique capabilities as an automatic data capture system in that they: Provide real-time, wireless transmission of data without human intervention; Do not require line-of-site scanners for operation; Allow stored data to be altered during sorting or allow workflow process information to be captured with the data; and Work effectively even in harsh environments with excessive dirt, dust, moisture, and extreme temperatures.