Atlantic alliance efforts provide common combat identification

Signal, May 1998 by Reed, Fred V

Technology for dismounted ground maneuver forces conquers recognition, improves soldier's awareness.

A four-nation working group of North Atlantic Treaty Organization countriesFrance, Germany, the United States and England-is agreeing in principle on common technology for a battlefield identification friend or foe system. This recognition system is planned for use with ground forces and helicopters. The technology chosen is a 36- to 40-gigaghertz interrogation and response system, which is being proposed as part of an alliance standardization agreement.

Those countries directly involved are anticipating that the technology will be available early in the next century, providing a partial solution to the fratricide that plagued coalition forces involved in the Gulf War.

At present, only two existing identification friend or foe (IFF) systems conform to the North Atlantic Treaty Organization (NATO) proposed standard. One is the U.S. battlefield combat identification system (BCIS), being developed for the U.S. Army by TRW, Redondo Beach, California. The other is the French Dispositif d'Identification au Combat (DIC), being developed by France's Thomson-CSF. The two companies are now working together under contract with their respective governments to make their versions of the technology interoperable. A TRW official asserts that the work is going well.

The systems are based on encrypted Ka-band interrogator/transponders. The French system will be 100 percent interoperable, Thomson-CSF officials claim, with the BCIS. The proposed IFF standard is a functional definition, not a hardware specification. Countries will be able to design their own equipment, provided it meets NATO standards and is interoperable with the hardware of the other nations.

A NATO combat identification working group tested systems from the four nations in Munster, Germany, last June. Four candidate systems competed, with the French and American being almost identical, according to Lt. Col. John D. Mahony, USA, the Army's product manager for combat identification at Fort Monmouth, New Jersey.

The British system, designed to be low cost, involves placing a continuously emitting beacon radiating in the M band at 94 gigahertz on all friendly vehicles. Friendly tank "shooter" platforms, as an example, detected the transmission during the demonstration with directional, highgain, coherent receivers. An advantage of the system is believed to be a low probability of interception (LPI) based on very lowpower transmission, coding and wideband frequency hopping.

The German system, which is transponder-based, operates in the D band at 1.090 gigahertz. The system also incorporates a laser interrogator that emits coded light pulses generated by an eye-safe solid-state laser. Infrared detectors on friendly platforms detect the pulses and respond with a radio frequency encrypted response picked up by the interrogating platform's directional antenna. This, said the Germans, demonstrates LPI and low probability of detection. The drawback is the inherently shorter range of lasers compared to millimeter wave radiating devices.

The French system and the American BCIS both operate in the 38-gigahertz bandwidth. The two countries agree that millimeter wave transmissions offer superior range under the adverse atmospheric conditions of the battlefield.

The Thomson-CSF system, like the BCIS, employs a highly directional interrogation antenna boresighted to the shooting platform's weapon-the main gun in the case of a tank, as an example. Transmission occurs whenever the tank's laser range finder is used. The ciphered interrogation is received by the omnidirectional antenna on the target vehicle, which immediately responds with an "I'm friendly" signal. Transmission-response time is less than a second, Thomson-CSF officials claim. The result-either friend or unknown-is displayed in the gunners' sight so that they do not have to move their eyes from the target. Correct identification occurs more than 99 percent of the time, the Thomson official emphasizes.

The angular width of the French interrogation beam is 2 degrees, which translates to roughly 100 meters at three kilometers. The French system's beam width corresponds to 22.5 mils in the BCIS. The effective range of identification is 6 kilometers ground-to-ground, and 8 kilometers helicopter-to-ground, according to Thomson officials.

The likelihood of interception or detection of IFF transmissions is low, those individuals directly involved maintain. Platforms radiate only when they are about to shoot. The interrogation lasts only 0.5 milliseconds, and the response is within 64 microseconds. Radiated power is low. The highly directional interrogating beam makes off-boresight detection unlikely. The transmitter employs high-speed frequency hopping and spread spectrum under the control of the encryption computer. The cryptocomputer is approved for both transmission and communications security by the National Security Agency and France's counterpartservice Centrale pour Securite Systeme d'Information (SCSSI).