An opportunistic array is an integrated ship-wide digital phased-array radar, where antenna elements are placed at available open areas over the entire shipâ s length. Such an array has the potential to fulfill many of the Navyâ s missions, including ballistic missile defence (BMD) where the radar mission encompasses exo-atmospheric surveillance, tracking and preliminary discrimination. Advantages of opportunistic arrays include enhanced stealth â since low-profile antennas reduce the shipâ s RCS; high angular resolution â as the entire shipâ s length forms the â apertureâ and produces a narrow beamwidth; and potentially lower costs â through the use of COTS technology and a flexible digital antenna architecture that reduces the number of distinct radar systems required. This research first investigated the opportunistic array concept in the context of BMD. A system level tradeoff was performed to size the system and verify that detection ranges greater than 1000 km could be achieved. Next, the research focused on designing a low-profile, broad-band U-slot microstrip patch antenna. Theoretical calculations and parametric studies were performed to develop an antenna element that could operate in the upper VHF/lower UHF frequencies. A set of simple design procedures is proposed to provide approximate rules that result in a good â first-passâ design with prescribed characteristics that require minimal tuning.