Officials of the U.S. Air Force and the Defense Advanced Research Projects Agency (DARPA) are looking for ways of using airborne radar to identify and protect friendly soldiers, tanks, ground vehicles, and helicopters. DARPA, of Arlington, Va., is working through the Air Force Research Laboratory Information Directorate in Rome, N.Y., to develop an extremely small and low-cost tagging device for infantrymen and vehicles that airborne search radar would identify as friendly. Air Force research contracts for the "Radio Frequency Tagging" project are going to Syracuse Research Corp of North Syracuse, N.Y. ($2 million), Northrop Grumman Corp. in Baltimore ($2 million), Lockheed Martin Tactical Systems Inc. of Litchfield Park, Ariz. ($1.4 million), and to Johns Hopkins University in Baltimore ($199,142). - J.K.