A surgical jamming system that can stop the enemy from communicating and navigating while minimizing disruption to friendly forces will be demonstrated under a new program launched by the U.S. Defense Advanced Research Projects Agency.

The Precision Electronic Warfare (PREW) program will demonstrate synchronization and pointing technology enabling multiple airborne and ground transmitters to work together to focus their jamming power on an area smaller than a city block.

Jamming systems now used in Iraq and Afghanistan to block the triggering of remote-controlled explosive devices via cellular or satellite telephones are effective, but interfere with friendly forces' communication and navigation systems over a wide area.

The PREW concept envisages a sparse array of 40 or more nodes transmitting precisely timed signals that combine coherently to jam radios within a small area while minimizing interference with communication and navigation services outside the target area.

The goal is to limit jamming to a spot about 100 meters in diameter. Instead of saturating receivers with barrage jamming, the system would degrade the quality of service within the target area to levels where wireless devices and GPS receivers are useless.

DARPA's broad agency announcement for the PREW program calls for a system that can jam across a frequency range of 200-2,700 MHz., covering 802.11g wireless and GMRS mobile radio services as well as classified target frequencies.

Individual jamming nodes would be lightweight and low-power -- typically 5 pounds and 7 kW. -- and low cost. DARPA says persistent low-speed airborne platforms are of interest, with the need for a low system cost favoring use of weather balloons.

Focusing the jamming power within a 100-meter-diamater spot from ranges up to 100 kilometers will demand extremely precise pointing and is likely to require the use of a passive or active beacon within or close to the target areas to assist in pointing the array, DARPA says.

A three-phase program is planned. The first phase would demonstrate clock synchronization across a 10-node ground array and the ability to project coherent energy; the second would demonstrate accurate pointing of the coherent energy from a 20-node airborne array. A third phase involving a prototype system comprising 40 airborne and ground nodes is expected to be the subject of a later solicitation, DARPA says. The PREW system is planned to transition to the user in fiscal 2013.

Image: DARPA