A basic Radio Frequency Identification (RFID) system consists of three components:
The antenna emits radio signals to activate the tag read and write data. The antenna is the channel between the tag and the transceiver, which controls the acquistion of data and the system communication. The antenna may have many forms and sizes and be installed in places like doors, to read information from people or objects that pass through it, or mounted into a toll cabin to monitor traffic in a highway, for example. The electromagnetic field produced by an antenna may be constant, but if continuous reading is not necessary, the field may be activated by a sensor.
Normally the antenna is enclosed with the transceiver and decoder to become a reader, which may be configured as a handheld reader or fixed reader to be connected to the central computer. The reader emits radio frequency waves with varied ranges depending on the reader and tag. When the tag goes through the electromagnetic field zone, the activation signal of the reader is detected. The reader decodes the data from the tag's integrated circuit and the information is passed to the computer.
RFID tags have a great variety of shapes and sizes. The tag used for animal identification may be less than 3 mm tall and 10 mm wide. Tags may be shaped as nails, to identify trees and wood articles, or as credit cards, for access control applications.
RFID tags are classified as active or passive. The actives are fed by an internal battery and are typically read/write. The tag data may be written and changed, depending on the application. The memory size varies according to the application's requirements — some systems work with memories of up to 1MB. The battery-assisted or active tag has a wider range, being readable up to 10 m away from the reader. But, there is the disadvantage of a bigger size and elevated cost, as well as the operational life, limited by the battery which can last 10 years at most.
Passive tags work without external power supplies 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 practically unlimited lifespan. The disadvantage is that they have shorter reach than the active tags and demand a more powerful reader for the data reading. Passive tags may be read-only or read/write.
The RFID systems are also distinguished by their frequency. Low-frequency systems (30 kHz to 500 KHz) have short read reach and low cost. They are more commonly 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 high reading reach and speed, are used for applications like locating of railroad cars and automatic toll services. However, better performance implies higher costs.
The significant advantage of all RFID systems is not needing contact or visual field to read the tag. Tags may be read through a variety of substances like water, mist, ice, paint, dirt, plastics, wood and environmental conditions where bar codes or any other optical technology would be in vain. The RFID technology also allows reading in challenging circumstances at notable speeds — in most cases, a response is given in less than 100 milliseconds. The read/write capacity of an RFID system is also a significant change in interactive applications, such as maintaining control, despite being a more expensive technology, if compared to the bar code. RFID is essential to a big variety of data collecting and identification applications that would not be possible with other technologies.
RFID technology developments keep improving systems with bigger memory capacity and reading ranges as well as faster processors. RFID technology isn’t going replace bar codes. Even with a price reduction, a tag with transponder will never be as cheap as a tag with a bar code. RFID will keep growing and establishing niches where the bar codes or other optical technologies lack the flexibility, range or features. As standards are defined for RFID systems, to make systems of several producers compatible, the RFID market will grow exponentially.
