Via Roland Piquepaille's Technology Trends weblog comes word of a radar tag sensor to eliminate friendly fire during combat.

Sandia National Laboratories, near the beautiful Sandia Mountains in New Mexico, USA, has announced development of a radar tag sensor that is mounted on military equipment. The sensor is used to track military vehicles and prevent fratricide through "friendly fire."

This new technology is what I would loosely call a "second cousin" to RFID -- in other words, distantly related. According to Sandia National Laboratories:

"The sensor, dubbed by the Army as 'athena' --- protector of the troops --- is not a radio transmitter that broadcasts a signal for the aircraft to receive. Instead, the sensor creates synthetic radar echoes, so that the radar picks up the sensor signal in the same way it picks up radar echoes from tanks, trucks, or other objects.

In general, the radar transmits a pulse of energy then looks for the reflections of that energy from objects on the ground. The tag sees the radar's transmitted pulse and sends it back to the radar, except it adds a little bit of data to the reflection (or echo).

As the radar picks up (or receives) reflections from the ground, it recognizes the tag's unique data signal and places an icon on the pilot's screen to alert him."

As some of the comments on Roland's weblog indicate, a key issue seems to be how to prevent the bad guys from reading the radar sensors, too. Otherwise, the whole purpose of the system would be foiled.