ODIN University - RFID education at your fingertips

Education leads to understanding. RFID has been labeled as complex, difficult, or even an art. The truth is that RFID is pure science — specifically physics.

From the very start of the company, ODIN has prided itself on having the best educated clients in the world. When our CEO Patrick J. Sweeney II published RFID for Dummies and CompTIA RFID+ Study Guide, many people said we were giving away our secrets. We feel just the opposite, we were teaching people to do it right. We knew we would keep innovating and getting better.

The following white papers, analysis and case studies should help you understand the physics and science behind RFID:

Five Elements of Success

Deploying an RFID Reader

This week read about Ultra Wide-Band RFID below:

Overview of UWB technology

Ultra Wide Band (UWB) refers to the radiation of RF energy such that the occupied bandwidth of the signal is extremely large as compared to conventional narrow band RF techniques; however the power is distributed across the bandwidth such that, in any small segment of the band, the power level is very low.

UWB is currently being tested and used in three functional areas: Short range communications such as wide personal area networks (WPAN), short range radar devices (vehicle anti-collision systems) and real time locating systems (RTLS), also known as UWB RFID.

A UWB RFID system consists of active transmitters (which are the tags), fixed location receivers and a host processor or hub. At least one tag is set in a precisely known position; this is called a reference tag. Tags radiate a UWB signal of a small number of bits (one system uses 60 bits) at a low duty cycle and at about 24 to 27 dBm spread over a broad frequency spectrum of 3.1 GHz to 10.6 GHz into a low gain antenna. The tags are roughly omni-directional and generally packaged in plastic cases (which avoid detuning issues that plague passive RFID solutions). The receivers note the signal, then note the time of arrival with a practical accuracy and granularity on the order of nanoseconds. The receivers are networked through Ethernet to a host system that correlates the differential times of arrival of the same tag signal from each receiver to triangulate the position of the tag.

UWB is currently allowed and regulated in the United States under CFR 47 part 15 subpart F or, in at least one case, paragraph 15.250 which is in subpart C. Under these current regulations, the maximum power across a 50 MHz segment of the band centered on the peak radiation is 0 dBm.

UWB for unlicensed devices was first permitted under part 15 of the FCC regulations in February of 2002. Commercial interests had been advocating for it at least since 1998. Interest has been in UWB for wireless data transfer communications, short range radar devices, and real time locating systems (RTLS).

Companies offering RTLS using UWB techniques have leveraged the term RFID, and these systems are now referred to as UWB RFID. These companies are advertising 650 ft ranges (line of sight) and 200 ft ranges (not line of sight). These companies report the ability to locate tags within buildings through building walls.

Key technology characteristics and innovation trajectory

Active UWB RFID tags offer advantages and disadvantages over passive UHF RFID. The advantages include continuously updated location information, longer range, and co-existence with narrowband RF systems.

UWB tags are low powered transmitters. The tag sends a short burst of pulses (each pulse being on the order of 250 picoseconds) at a low repetition rate (for example, 1 to 40Hz). The receivers pick up the tags and the hub calculates the tag location from the differential time of arrival (DTOA) provided by the receivers. The hub then passes that location to a back-end program for use. Theoretically, this program can update the position calculation at the same repetition rate. In practice, it will be somewhat less.

A new innovation in the development of the tags is a wireless control link from the receiver or the hub that changes the characteristics of the transmitter tags; for example, the update rate. This link is normally a narrow band signal in one of the ISM bands. This might allow dynamic control to increase precision of tracking moving items while minimizing data flow for stationary items.

UWB systems can co-exist with existing RF systems. Although detectable energy can be discovered within the ISM bands at 2.45 GHz and 915 MHz, the levels are much too low to interfere. Because of the broad bandwidth, those systems should generally not interfere with the UWB RFID.

Since the readers are only receivers, they can be much more sensitive than a UHF RFID transceiver receiver section. This translates to longer range, range doubling for every 6dB improvement in sensitivity. Since the tags are transmitters rather than backscattering devices, the signal will be orders of magnitude larger.

Nothing is without a cost, and this is true of UWB RFID as well. There are several disadvantages, some inherent and some that should be mitigated as technology improves.

MSSI tags are reported to cost $40 each, with large order discounts bringing them down to only $15 (large order is undefined). Time Domain PulseON tags, available from Parco Merged Media, are ballparked at $30 - $35.

Current FCC regulations may keep these tags from being used outside. There are three paragraphs of the FCC regs that relate to UWB systems. One allows for indoor use, one allows outdoor handheld use, and a third, which is more restrictive, that allows more general use. The signal levels for the outdoor and general case are lower. The Time Domain tags are advertised for indoor use. The MSSI Sapphire Dart system is approved for indoor and outdoor use.

These tags are battery-powered. The manufacturers are probably advertising optimistic battery life. Any deployment should include a plan for periodic test and battery replacement.

Beyond the regulatory framework that has been erected by the FCC, there are no standards around UWB RFID. Efforts by the IEEE that commenced in 2003 to establish a UWB standard around communications (short range consumer devices) fell apart in 2005 as two different communications technologies could not achieve domination in the standards group. Similar efforts have not even been started around UWB RFID.