Metal‐only ultra‐wideband reflectarray

A metal‐only ultra‐wideband polarisation‐selective reflectarray element using the true time delay is proposed herein. The element affords a large bandwidth with a tuneable reflection phase. An offset‐fed reflectarray prototype using the proposed element was designed, and it exhibited stable radiation patterns from 4 to 35 GHz (over 8:1 bandwidth), a low loss, and a measured maximum efficiency of 54.6%. The special metal‐only feature circumvents the need for dielectric substrates and ground planes; such features result in a simple structure that allows it to be used in harsh environments such as space.