True Time Delay in Phased Arrays

Abstract

This paper reviews the topic of true time delay (TTD) and its importance and implications in wideband imaging phased arrays. The paper describes an early analog version of TTD using the “Rotman lens,” discusses various architectures, and talks about photonic implementations. Also emphasized are the differences in design between narrowband arrays which are calibrated at individual frequencies and wideband imaging arrays where TTD is necessary.