September 2008

The ABCs of RFID

By Sam Liu

Radio frequency identification is an automatic identification system used to increase operational efficiency in industries such as transportation, construction, manufacturing, and aviation.

Utilizing RFID tags and readers, users can create an automated tracking solution that provides real-time inventory visibility, operational status, movement of assets thru a supply chain, and safety and security for people.

RFID has been around for decades-mostly in the form of low frequency (LF) and high frequency (HF) technologies that often are for control and close proximity tracking. 

RFID is also in many automated tollbooth applications. Recently, a new breed of RFID operating in the ultra-high frequency (UHF range) has emerged to help optimize the operational supply chain and closed loop asset tracking. Based on EPCglobal C1G2 standards, this type of RFID enables the tracking of assets at longer distances than LF or HF (usually up to 30 ft) and can process tags at a higher speed as well as bulk quantities.

However, as the RFID market grows and enters new industries and applications, existing technologies are finding their limits. These include, but are not limited to longer read ranges (e.g. beyond 50 ft), extended rewriteable memory on the tag (e.g. 64Kb), external inputs (e.g. temperature sensor), and the ability to withstand real-world challenging environments such as moisture, temperature, and dust.

To be fair, there is a class of RFID known as "active RFID" that can provide much of the advanced functionalities mentioned above and even more. However, these can be quite costly, actively transmit signals, or are proprietary technologies. However, some applications, such as in the case of the military, do warrant the price and functionality of these types of tags.

Now enter battery-assisted passive (BAP) RFID, also known as semi-passive or semi-active. This class of RFID has some of the characteristics as C1G2 RFID (e.g. passive transmission, UHF based) as well as those of active RFID (e.g. longer range, memory, sensor inputs, etc.). However, the price performance of these tags is at a fraction of active RFID. BAP RFID utilizes a battery to increase the listening sensitivity and transmission power of the tag, thereby achieving a range of 50 meters or more. Moreover, because it does not actively transmit a signal, the battery life can be five years or more. The built-in battery and extended memory also allows these tags to have on-board sensors, without requiring external power or devices.

There is no "good or bad" RFID technology. It all depends on the application and economics of the solution. Combined though, these new flavors of RFID will enable a completely new world of applications-applications that could not have happened with either barcode or human intervention.

As RFID continues to grow, companies are finding new uses of the technology and utilizing it to provide real-time visibility into business operations. Combined with the right business process, RFID can add tremendous improvements to operational efficiency and a company's bottom line.


Sam Liu ( has 20-plus years experience in RFID technology. He works in the U.S. and Asia Pacific regions now as a director at Intelleflex Corp. (, which integrates radio systems into myriad industries and solutions.

It's elemental, Watson

RFID technology breaks out in two major classes.

There are passive tags that have no energy source and draw their operating power from the RFID reader and active tags that include a power source, such as a battery in the tag.
The battery power source can increase the communication range as well as support logging of sensor data without a reader field being present.

The frequencies are these:

Low frequency (LF): 125 to 134.2 kHz and 140 to 148.5 kHz. Typical applications include immobilization systems in automobiles, retail, and animal identification and tracking through the human food chain.

High frequency (HF): 13.56 MHz. Typical applications include tagging of rental items like books or uniforms, public transportation ticketing, pharmaceuticals, and other item tagging.

Ultra-high frequency (UHF): 860 MHz to 960 MHz. Typical applications include fixed asset tracking, baggage handling, and supply chain applications.