A basic RFID system consists of three components:

• Antenna or coil
• Transceiver (with the decoder)
• Transponder (known as tag), electronically programmed with data

The antenna emits radio signals to activate the tags, read and write data. The antenna is the channel between the tag and the transceiver, which enables the acquisition of data by the communication system. The antenna can have different shapes and sizes, and can be installed in places such as doors to capture the tag data identifying people or objects that go through the door, or an antenna mounted on a toll booth, to monitor the traffic on a highway, for example. The electromagnetic field produced by an antenna can be constant, but if continuous reading is not necessary, the field can be activated by a sensor.

Usually the antenna is packaged with the transceiver and decoder to become a reader, which can be configured as a data collector or a fixed reader to be connected to a PC. The reader emits radio frequency waves with several ranges depending on the reader and Tag type. When the tag passes through the area of electromagnetic field, the reader activation signal is detected. The reader decodes the data encoded in the microchip of the tags and the data is transfered to the computer.

The RFID tags have a variety of shapes and sizes. The tag used for animal identification may be less than 3mm in diameter and 10 mm in length. The tags can be in nail form, to identify trees or wood items, or a credit card, to be used in applications for access control.

RFID tags are classified as active or passive. Active tags are powered by an internal battery and are typically used for read/write mode. The data from tags can be written and modified according to necessity. The memory size of active tags varies according to the application requirements – some systems operate with up to 1MB of memory. The tag with an internal battery achieves a greater read distance and can be read up to 10m away from the reader. However, there is the disadvantage of larger size and an increase in cost, in addition to the operational life limited by the battery that can last up to 10 years.

Passive tags operate without a power supply and are activated by the electromagnetic field emitted by the reader. They are consequently much lighter and smaller than the active tags, much cheaper and offer a virtually unlimited operational life. The disadvantage is that they have less reading distance than active tags and require a more powerful reader to collect the data. They can be read only or read/write.
RFID Systems can also be distinguished by frequency. Low frequency systems (30kHz to 500kHz) have a short range and low cost. They are frequently used in access control and animal identification applications. High frequency systems (850 MHz to 950 MHz and 2.4 GHz to 2.5 GHz) with long range and high speed reading are used for applications such as railroad car tracking and automated toll payment. However, the best performance in the high-frequency systems, means higher costs, but quite often with a very good Return on Investment.

The biggest advantage of all RFID systems remains in the fact that they don’t require any contact or field of vision to read the tag. Tags can be read through a variety of substances such as water, fog, ice, paint, dirt, plastics, wood and environmental conditions where barcode or any other optical technology would be impracticable. RFID technology also allows reading in difficult environment conditions and at remarkable speeds – in most cases a read can be made in less than 100 milliseconds. A RFID system read/write capacity is also an important advantage in interactive applications such as maintenance management. Despite being a technology more expensive when compared to barcode, RFID has become essential for a variety of data collection and automated identification applications that would not be possible with other technologies.

Developments in RFID technology continue to improve the system with greater memory capacity, greater range of reading, and faster processes. It is very difficult for this technology to replace the barcode – even with lower prices; a label with transponder will never be as cheap as a label with a bar code. However, RFID will continue to grow in its established niches where the barcode or other optical technologies are not effective. Industries will continue to develop standards and applications for RFID systems and with that the market for RFID will grow exponentially.