Radio frequency identification (RFID) technology combines touch memory technology with the ability to interrogate data content, without contact and the necessity for line-of-sight communication.

RFID is a relatively new automatic Identification technology, first appearing in tracking and access applications during the 1980s. These wireless systems allow for non-contact reading and are therefore effective in manufacturing and other hostile environments where barcode labels could not survive. RFID has established itself in a wide range of markets including livestock identification and automated vehicle identification (AVI) systems because of its ability to track moving objects. The technology has become a primary player in automated data collection, identification, and analysis systems worldwide.

The basic RFID system consist of three components: An antenna or coil, A transceiver with decoder, A transponder (often called a tag) that is electronically programmed with unique information. Often the antenna is packaged with the transceiver and decoder to become a reader (or interrogator), which can be configured either as a handheld or a fixed-mount device.The antenna emits a low powered signal that generates a response from the circuitry within the tag. The resulting radio or microwave transmission or electromagnetic induction (depending on the type of tag) is received and interpreted by the transceiver. Antennas are available in a variety of shapes and sizes, which means that they can be built into a doorframe or indeed any object to receive tag data from passing persons or articles. The electromagnetic field produced by an antenna can be constantly present when multiple tags are expected continually. If constant interrogation is not required, a sensor device can activate the field. RFID tags are categorised as either active or passive.

An active tag is powered by an internal battery, which generally gives it a longer read range than passive tags, which obtain operating power from the reader. Active tags are also usually read/write in comparison with typically read-only passive tags. While active tags can operate with up to 1MB of memory compared to the 32 - 128 bits of passive tags, the former are larger, heavier and more expensive than passive tags, which offer a virtually unlimited operating existence in contrast with a maximum active tag lifetime of 10 years. In addition to the lesser memory size, passive tags also have shorter reading ranges and require readers with higher power than those used with active tags. RFID systems are also distinguished by their frequency ranges. Low-frequency (30 KHz to 500 KHz) systems have short reading ranges and lower system costs. They are most commonly used in security access, asset tracking, and animal identification applications. High-frequency (850 MHz to 950 MHz and 2.4 GHz to 2.5 GHz) systems, offering long read ranges (greater than 90 feet) and high reading speeds, are used for such applications as railroad car tracking and automated toll collection. However, the higher performance of high-frequency RFID systems incurs higher system costs.

ADVANTAGES

The significant advantage of all types of RFID systems is the non-contact, non-line-of-sight nature of the technology. Tags can be read through a variety of substances such as snow, fog, ice, paint, crusted grime, and other visually and environmentally challenging conditions, where barcodes or other optically read technologies would be useless. RFID tags can also be read in challenging circumstances at remarkable speeds, in most cases responding in less than 100 milliseconds. The read/write capability of an active RFID system is also a significant advantage in interactive applications such as work-in-process or maintenance tracking. RFID has become indispensable for a wide range of automated data collection and identification applications that would otherwise be impossible.

COMMON APPLICATIONS

Animal Identification, Security access and egress, Anti-theft retail systems, Asset and inventory tracking, Automatic toll collection Wildlife and livestock tracking, House-arrest monitoring systems, Manufacturing work-in-process data, Shipping, container and air cargo tracking, Fleet maintenance, Railway car tracking

Active tagging is a relatively new addition to the RFID portfolio. The tag is a battery powered self-contained data transponder.

The smallest tag size is equivalent to a standard credit card footprint, with a thickness of approximately 5mm. Larger tags are available for industrial applications.

The reading equipment is a low cost UHF receiver, with options of several different antennas. The antenna selection will dictate the range at which the tag is to be read.

Typical read ranges are from 25mm to tens of metres. The tag is factory set to burst data at pre-determined periods, the standard being 800Ms (0.8 of a second).

With this repetition rate the tag has a life of approximately five years. Repetition rates can be adjusted to suit the application.

Each data burst contains the site code of the tag, a unique number, time stamp and alarm status. RS232, RS485, Ethernet or wireless technology can connect the receiver network to a controlling PC.

Tags are available with anti-tamper, tilt and motion, and standard options. Typical applications can be Art tracking, asset tracing, reading container contents whilst moving etc.

Passive tag technology was designed to meet the needs of high volume users, the tag devices being small, low cost, short-range devices. Passive technology is generally used for access control, and applications where high-speed data collection is not required. The tag contains no power source, and receives energy from the reading device. The reader is a radio transmitter and antenna system designed to accept the very weak radio signal form the tag, once energised. Tags may be read only, or read write, with the ability for the user to update and therefore hard code information to the tag. Typical applications are for hands free access control, pet and animal tagging inventory management, and asset control. Tags range from miniature 2.12mm glass inject able tags for pet identification, to specialist 50mm and above tags for industrial applications. Tags may be programmed with unique or sequential identification markers, and are available in many sizes and formats.

PASSIVE TAGS - HIGH & LOW FREQUENCY

To further confuse matters passive tag systems can be sub-categorised into low and high frequency technology. Low frequency is generally used for single or sequential tag read applications, where a large quantity of tags is required. High frequency systems are used for applications where multiple tags are read simultaneously, often as many as 25 or 30 tags at a time. High frequency systems generally have superior anti-collision properties, typical applications include clothing audit, document tracking etc.