Array technology has progressed primarily because of limitations imposed by practical engineering; by the cost, size, weight, manufacturability, and the electromagnetic issues of polarization, sidelobe and gain requirements, the limitations of phase, and amplitude control and reliability. These have driven the whole technology to invention and progress. In the 11 years since the first publication of this book, these stimuli have led to much more extensive use of printed antennas, conformal arrays, solid-state T/R modules, time-delay devices, optical and digital beamforming, and a variety of new and more powerful methods of computation and synthesis.