Reflectarray Element Based on Aperture-Coupled Patches With Slots and Lines of Variable Length

A phase-shifter element for printed reflectarrays with more than 4 cycles of phase delay is presented in this work. The proposed reflectarray element allows very linear phase curves and is based on the combination of two previously studied and demonstrated concepts: variable length slots on a ground plane and patches coupled through a slot to variable length lines. In the former, the slots act as inductive loading on the patches depending on their length. With the second concept, the effect of nonconstant path delay is alleviated by the introduction of true-time delay (TTD) lines. The mixed effect allows a much larger range of phase delay to be reached and at the same time to improve the linearity of the phase delay behavior. Two ways of increasing the phase delay range are shown: the increase in length using U-shaped delay lines and the use of high permittivity substrates