Wideband, Beam-Steerable Reflectarrays Based on Minimum-Switch Topology, Polarization-Rotating Unit Cells

Abstract

We describe the results of a wideband, reconfigurable reflectarray concept based on polarization-rotating unit cells (PRUCs) with a minimum-switch topology design. To enhance the simplicity and decrease the cost, the approach focuses exclusively on a one-bit phase shifting architecture. We investigated PRUCs having four conducting, single-headed arrow structures on their top surfaces and crossed, conducting strips acting as hard-wired switches on their bottom surfaces. The top-surface arrows and the bottom-surface strips are connected with four vertical vias. The switch states of the bottom conducting strips determine the two operating states of the unit cell for rotating the polarization of the reflected waves by +90° and -90° with respect to that of the incident, linearly polarized waves. The PRUC provides a co-polarization reflection coefficient of better than -1 dB over the wide frequency range of 8-12 GHz, as demonstrated by the simulation results. The PRUCs were incorporated into an illustrative reflectarray operating in the X -band. The full-wave simulation results show good beam scanning performance over the range of ±45° with a maximum scan loss of 3 dB. Two static realizations of the reflectarray for beam collimation at θ =0° and θ =45° in the x z plane were fabricated and experimentally characterized. The measurement results show good agreement with the simulation results and demonstrate the beam steering operation of the proposed reflectarray.