Felling Antenna Forests ONR's AMRF

As the services scramble to adapt to 21st century visions of "network-centric warfare" that call for vast growth in tactical information exchange, they'll be looking for innovative ways to multiply communications networking capabilities—while slashing costs.

All the services are looking at "transformation" initiatives that demand greater command, control, communications, surveillance, intelligence, and electronic warfare performance for joint operations. The Navy, out in front of the other services on the information-networks front, has introduced a new initiative, called FORCEnet, that stresses urgently the need to network command and control, weapon, and sensor systems among ships, aircraft, and ground units.

The upshot, operators and technologists say, is ever-greater dependence on radio-frequency (RF) bandwidth, and, unless another approach is identified, more antennas, transmitters, receivers, and the accompanying complexities of operating and supporting new RF systems. The Navy has met each new functional requirement for use of the RF spectrum with a new antenna, each needing new auxiliary equipment, operator training, and maintenance and logistics support.

The ever-growing reliance on RF connectivity in recent years—actually recent decades—has spawned a forest of antennas on Navy ships for multiple communications, radar, and electronic warfare systems, all which transmit and receive at different frequencies. The number of antennas aboard aircraft carriers, amphibious ships, cruisers, and destroyers delivered in the 1990s has increased more than 100 percent over the number of antennas aboard ships delivered in the eighties.

Antenna growth—apart from the continuously increasing procurement and maintenance costs of individual "stovepipe" antenna types—has increased ships' radar cross-sections. The need for new antennas also has required extensive modifications in ship design to manage the added weight, as well as complex restrictions on use to minimize dangerous electronics interference.

The solution, in the emerging age of information warfare, won't be in limiting the use of the RF spectrum. Ships, aircraft,, and even ground vehicles—will need more bandwidth, not less.

Instead, managers of Navy ship and aircraft programs are looking at pioneering work sponsored by the Office of Naval Research to develop new multi-function radio-frequency concept (AMRF-C) antenna apertures that use software to modify common apertures for multiple RF systems. The AMRF-C approach, which eliminates the need for additional hardware, would enable ship designers to pare back dramatically the microwave "antenna farms" that have proliferated aboard ships now in service, while meeting future requirements, expanding the effectiveness of sensor, communications, and electronic warfare systems, and reducing RF cross section.

ONR scientists say that the AMRF-C effort, as the name implies, will integrate radar and communications functions in a few sets of high-performance transmit and receive antenna apertures.

AMRF-C apertures also will integrate electronic warfare systems, which detect, jam, or deceive enemy radars and weapons.

Joe Lawrence, director of ONR's surveillance, communications, and electronic combat division, says that the AMRF-C effort aims at overcoming the antenna-proliferation crisis, with all the cost, ship-design, and operational problems it creates. Instead of separate transmit and receive apertures for each of the multiple radar, communications, and electronic warfare systems, a few pairs of AMRF-C apertures would handle most microwave RF functions. Some applications, such as theater ballistic missile defense, would continue to require unique systems.

The AMRF-C approach, Lawrence says, addresses squarely the design, systems-engineering, and maintenance problems that confront the developers of requirements for the Navy's future surface ships, while offering major savings to the ship program managers through the elimination of many costly RF apertures.

ONR initiated the AMRF concept work in the mid-1990s and continues to direct it. The Naval Research Laboratory is coordinating the development of an AMRF-C test bed. Other Navy labs, including the Space and Naval Warfare Systems Command, based in San Diego, and the Naval Surface Warfare Center's Dahlgren division in Dahlgren, Va., are helping with component development and ship integration, respectively.

The Navy's most experienced systems integrators in industry also are supporting the work. Lockheed Martin's Moorestown, N.J. surface-ship group is working on high-band receive array and receiver technology. Raytheon Electronic Systems is developing signal and data processors, and Northrop Grumman is developing low- and high-band arrays.

ONR already has sponsored some early component demonstrations. More demonstrations are set to start early in 2003, aiming at a fully integrated demo in mid-2004.

Lawrence points out that AMRF-C technology already is "backing into" the fleet. Boeing, under contract to Raytheon for work on the systems architecture for the surface Navy's high-profile DD(X) next-generation destroyer, is using AMRF software for the resource allocation manager for the DD(X) sensor, weapon, and inventory-control system. Northrop Grumman Ship Systems and Raytheon also are looking at a solid-state transmitter developed by Northrop Grumman for a DD(X) electronic warfare system.

The Navy's cruiser conversion program, which will field a number of warfighting upgrades for Ticonderoga-class Aegis cruisers, is pursuing a common aperture development program that will incorporate AMRF-C transmitter and receiver technology.

The AMRF-C vision is far-reaching. The Army's biggest "transformation" program, development of a highly integrated future combat system (FCS), is looking at multi-function array technology that AMRF-C could provide.

The Pentagon-mandated joint-service joint tactical radio system, or JTRS, is based a common architecture, to be modified by software for diverse communications applications, echoing the AMRF-C approach.

Meanwhile, Navy acquisition leaders have declared that they're looking for innovative design and systems-engineering approaches to achieve procurement savings that can by plowed back into warfighting. They're also seeking "process improvements" that will permit ship program managers to reach across organizations, to field technologies and systems developed outside their own organization. As the new ship programs move to face the complex challenge of integrating RF systems, the AMRF-C mix of technologies will be available.