Radio-frequency (RF) tags, or simply “tags,” are small electronics devices used for communications in a wide variety of tagging, tracking, and locating (TTL) applications. The common feature of all RF tags is the use of radio frequencies (kHz -> MHz -> GHz) over the air as an information-transport layer.

Differing from traditional radios, RF tags typically do not convey real-time voice communications. Fundamentally, the job of the RF tag is to provide some measure of information back to another entity (the “interrogator”), be it a locating signal, data (ID, sensor information, etc.), or a synthetic radar echo. Unlike a radio, a tag is usually intended to be “autonomous” (no human input required); however, many tags take command and control instructions directly from a user or host.

Common Features of RF Tags

Tags may be as simple as a tiny RF switch providing a 1-bit “yes/no” response, and they can be as complex as high-speed signal-processing devices in a complex communications channel.  Typically a Tag integrates the electronics, antenna, and batteries in a single package. The list below includes many common features of RF tags. In some cases, one or more of these features is not included in the tag, but rather as a “next-level assembly.” Arguably, integration of more of these features creates a more useful tag!

Common Tag features include the following:

• RF transmitter, or transceiver

• Antenna(s)

• Internal battery and/or external power port

• Control and timekeeping electronics with embedded software and hardware

• Internal sensors (temperature, movement, GPS, etc.)

• External data I/O ports

• Efficient mechanical and environmental packaging

The Tag-System Concept

An RF tag does not exist in a vacuum; instead, in a system sense, it co-exists with the interrogation device and operates in a dynamic environment. The tag must therefore be designed not only for the RF communications channel, but its design must consider intended operational procedures, the user community, environmental concerns, and co-existence with other communications systems.  A major design factor can be procurement cost.

Sandia TTL expertise was born out of and has grown along with our long history of building radar systems (http://www.sandia.gov/radar/). In parallel with Sandia’s fuzing, SAR, and MTI radar development, Sandia’s RF tag technology has branched into every kind of radar, communications, and monitoring application.

Sandia applies a system-centric approach to RF tag development regardless of application. Indeed, some programs desire “black box” designs, whereas some programs develop complete tag-interrogator systems. In either case, Sandia attempts to understand the complete tag-system concept to maximize utility and effectiveness. To solve difficult problems, Sandia tag engineers, radar engineers, and system analysts work together and share experiences and new ideas.  Interaction with the customer and user community is also critical.  We believe this interaction is vital in order to provide robust solutions for our Nation’s TTL missions.

RF Tags vs. RFID

Commercial RFID (radio-frequency identification) tags are widely used in toll/access applications and are now making headway into item tracking. Sandia RF tags differ from these devices in several fundamental ways. The table below describes the many differences between COTS RFID and Sandia TTL applications.

Though COTS RFID tags are not a primary focus at Sandia, we have in-house expertise in this area. Several staff have worked in the RFID area and have consulted on commercial and government RFID ventures and evaluations.

Independent Organization

Sandia National Laboratories is a Federally-funded research and development center (FFRDC). As such, one of our primary missions is to develop critical technology for our Nation’s missions and transition that technology into manufacturing or to an outside entity as appropriate. Sandia works with numerous organizations, both government and commercial, to advise and to develop solutions to many types of tagging problems. Where the solution requires technologies that go beyond what is currently available, Sandia can help design a solution and transition that solution to a partner organization. We take pride in the fact that government and leading commercial entities put their trust in Sandia to deliver hardware for real-world applications.