Abstract: Ultra-wideband phased array antennas play a significant role in multifunctional integrated electronic systems. Traditional antennas deployed independently in multiple systems can be replaced by them, and highly integrated functions such as reconnaissance, jamming, detection, and communication can be achieved. For particular application platforms like high-speed aircrafts and artificial satellites, significant technical challenges are faced by the development of such antennas in achieving low profile, lightweight, low cost, and low radar cross section (RCS), while excellent wideband and wide-angle radiation performance is ensured. To overcome these challenges, three designs for ultra-wideband phased array antennas are proposed in this paper, which focus on low profile, lightweight and low-cost construction, and RCS reduction, respectively. The feasibility of the proposed design methods is verified by the measured results of fabricated antenna prototypes.