A basic Radio Frequency Identification (RFID) system consists of: an antenna; a transceiver with a decoder; and a transponder (also known as an RFID tag). Without software to utilize the information derived from reading the tags, however, the system would have little practical value. So it is wise to include middleware as a component.

A transponder, or tag, is electronically programmed with unique information sometimes as little as an identification number so the item it is attached to can be located and tracked. Some RFID tags are much more sophisticated. Electronic passports based on RFID technology, for example, can include biometric data about the passport holder and encryption capability as well.

When an antenna is packaged with a transceiver and decoder, it becomes an RFID reader. Depending on their output power and RF frequency, readers have ranges of from an inch to 100 feet or more. When an RFID tag passes through the reader's active zone, it detects the reader's activation signal. The reader decodes the data encoded in the tag's RFID chip and the data is sent over the wired communication infrastructure to corporate, institutional, of governmental databases where it is included in databases.

In the basic system, the antenna emits RF signals to activate the tag and read and write data to it. Antennas are available in a variety of shapes and sizes depending on the application. They can be attached to any number of retail items such as clothing, inserted under the skin of livestock, or mounted on toll booths to monitor traffic passing by on a freeway.

When a steady stream of tags is expected in the application, the electromagnetic field produced by an antenna can be on all the time. But if constant interrogation is not required, the field can be activated by a sensor.

Tags vary in their technological sophistication and capabilities. Regardless of the type of tag, however, since there are always far more tags than readers in a system cost is a controlling factor. In many systems, the tags are discarded or destroyed.

Software consists of the embedded systems software that runs the hardware and middleware, which connects the local RFID system to corporate, governmental or institutional databases. In almost all RFID applications, middleware is by far the single most expensive part of the system.

Click here for Figure 1
Figure 1: RFID system components.

Passive RFID tags>
Passive RFID tags do not have internal power supply. Instead, they are powered by energy induced in the antenna by the RF signal. Most passive tags transmit by backscattering the carrier signal from the reader. The engineering challenge is to design an antenna that can collect power from the incoming signal and transmit it to the outbound backscatter signal. The response of a passive RFID tag is not necessarily just an ID number; the tag chip can contain non-volatile EEPROM for storing data.

Hitachi, Ltd. presently holds the record for the smallest passive tag. Its μ-Chip measuring 0.15x0.15mm (not including the antenna) is thinner than a sheet of paper. (7.5 micrometers). It transmits a unique 128-bit ID number hard coded into the chip as part of the manufacturing process and has a read range of 30 cm.

The lowest cost RFID tags cost about 5 cents each. Adding an antenna creates a tag that varies from the size of a postage stamp to the size of a post card. Passive tags have practical read distances ranging from about 10 cm to a few meters. Their simple design means that a printing process can be used to manufacture passive tags.

Active RFID tags Active have an internal power source, which makes them more reliable and provides a wider range of operation. Their higher reliability is derived from the tag's ability to conduct a session with a reader during which transmission errors can be detected and corrected.

Many active tags have practical ranges of hundreds of meters, and a battery life of up to 10 years. Active tags can have a range of up to 300 feet and they typically have larger memories than passive tags, as well as the ability to store additional information sent by the transceiver. Presently, the smallest active tags are about the size of a coin and sell for a few dollars.

Due to the wide range of applications RFID continues to develop based on new standards and improvements in the technology and design. A few of these challenges include HF gen 2 standards, Near Field UHF technology, as well as mature and off-the-shelf hardware and sensor technology.