The Integrated Electronic Warfare Systems business unit of BAE Systems in early September delivered the 100th surface ship identification friend/foe (IFF) targeting antenna—known as the AIMS antenna—to the Navy since the company (then the Sanders unit of Lockheed Martin) started building the unit in the early 1990s.
In mid-summer, the Navy awarded BAE a new contract for ten additional antennas. Six will go on board Arleigh Burke (DDG-51)-class destroyers DDG-105 and -106 and the Nimitz (CVN-68)-class carriers Carl Vinson (CVN-70), John C. Stennis (CVN-74), Harry S. Truman (CVN-75), and George H. W. Bush (CVN-77). The Republic of Korea Navy will get three units for its KDX-3-class destroyers, and one will go on board the Japanese destroyer Kongo. The Spanish Navy also is purchasing the antenna unit for its F-100 destroyers.
For the U.S. Navy configuration, the antenna unit (designated the OE-120 AIMS) is integrated with the UPX-37 interrogator, built by the BAE Systems business unit in Greenlawn, New York, and the UPX-24 interrogator processor, provided by Litton Data Systems. The three components make up the shipboard IFF system, formally designated the "air-traffic-control radar beacon system/identification friend/foe Mk 12 system." The system now is fielded on board Ticonderoga (CG-47)-class cruisers, Nimitz-class carriers, Arleigh Burke-class destroyers, and Wasp (LHD-1)-class amphibious warfare ships. The AIMS also is slated for the Navy's planned 12 San Antonio (LPD- 17)-class amphibs.
Steve Dichard, BAE's manager of the AIMS antenna program, points out that the AIMS is exclusively a tactical IFF system, and is not used for air-traffic control. The carriers, which employ the AIMS system for IFF, are fitted with a TPX-42 IFF interrogator beacon system used exclusively for air-traffic control.
The electronically steerable antenna, a 12.5-foot ring fitted high on board a deckhouse mast, consists of 64 radiating elements that transmit the IFF beam either on a continuously scanning 360[degrees] path or directed at any of 1,024 positions while the array remains stationary. The path of the beam can be redirected by the below-deck interrogator and processor within ten milliseconds. The interrogator and processor are linked to the ship's combat system or (for new-build carriers, the Wasps, and the San Antonios) with the ship self-defense system Mk 2. The combat system obtains track information from air-search sensors for cueing for IFF operations and weapon-launch decisions. The antenna transmits an interrogatory signal at the standard IFF frequency of 1,030 megahertz. Nonhostile contacts respond at the standard 1,090 megahertz.
The UPS-24 interrogator integrates the IFF function with the ship's command-and-control systems and displays and responds to requests for IFF information on aircraft as well as surface targets. Friendly aircraft contacts equipped with transponders provide a response; hostile contacts provide no response.
Dichard points out that the company, as Lockheed Martin's Sanders unit, inherited the AIMS design from Lockheed's old Electronics Company in Plainfield, New Jersey. The antenna program was criticized in the early 1990s for reliability and maintainability problems. The company carried out an extensive redesign and improved the system's mean time between failure rate to 20,000 hours, and won an excellence award from the Navy's Aegis program office. The improvement persuaded the Navy to drop plans to seek a second source, and now BAE Systems has won a number of sole-source production contracts.
While the company will continue to provide the AIMS antenna to international customers, the buys for the Arleigh Burkes and the San Antonios probably represent the final U.S. Navy fielding of the large donut-shaped AIMS antenna. Future ship programs will seek innovative ways of reducing signatures by embedding antenna arrays in deckhouse structures, as with the SPY-1 array panels on board the Aegis ships. The stringent requirements for minimizing signatures also will eliminate the tall masts that today serve as highly visible perches for multiple communications, radar, and electronic warfare antennas. The AIMS ring design will not be a candidate for the DDX landattack destroyer, CVN-21 next-generation carrier, or the littoral combat ship.
Dichard points out that the AIMS antenna is a component, not a system, and to compete on the new programs would require a teaming arrangement with a systems integrator. He says, however, that BAE is looking conceptually at new designs for its IFF array technology that focus on embedded paneled arrays.