Wideband subarray systems: evolution of a research area

R.W.P. King has always insisted that his students look beyond the trivial to uncover the subtleties that, (more often than not) require detailed electromagnetic analysis and reveal fundamental properties. The purpose of this paper is to look at an important topic in scanning arrays to show how the interaction of obvious geometrical features and very subtle electromagnetic features are shaping this evolving technology. This paper discusses developments in the technology of transform-fed wideband scanning arrays. These antennas were introduced over 40 years ago, and proposed for a large number of scanning applications, but because of poor efficiency and high cost, have not found application in fielded systems. However, technological innovations including MEMS phase shifters and digital beamforming have re-focused attention on these systems, which for many applications remain the most viable array architecture for large wide band arrays.