A physical layer open architecture for communications systems integration: Common baseband processor with multiple-access adaptively steered antenna array

Fighting the Global War on Terrorism and sustaining Homeland Defense requires that todaypsilas military platforms, such as E-2 and Global Hawk, and future platforms such as Joint Strike Fighter, support network-centric operations with advanced on-board sensing and communications capabilities demanding high-gain antenna coverage over a large RF spectrum. In the typical radio system integration seen today, a platform can include several radio functions, including communications terminals and intelligence, surveillance, and recognizance (ISR) receivers and other sensors, each of which is tightly coupled to its own antenna or antenna system. The challenge is that many of these platforms have limited surface for antennas or antenna arrays, so multiple antenna arrays to provide steerable gain for each sensing and communications function is impractical. Moreover, a single antenna array that allows independent beam steering for multiple radio functions using banks of RF switches and mixers at the antenna elements can be even more intractable. This paper will present an open architecture (OA) for the physical layer of radio systems integration in which the digital baseband I/Q signals of every radio function in the system, both transmit and receive, pass through a common baseband digital processor. This architecture allows multiple, independently steered beams to be formed simultaneously, at independent frequencies, from a single antenna array, thereby maximizing the efficient use of the antenna resources of platforms having multiple radio functions. This multiple-access-array capability is achieved by applying separate beamforming weights and separate IF modulations to the digital baseband signal of each radio function in the system.