Wideband, Beam-Steerable Reflectarray Antennas Exploiting Electronically Reconfigurable Polarization-Rotating Phase Shifters

Abstract

We present a wideband reflectarray antenna with electronic beam-steering capability. The beam-steerable reflectarray uses an electronically reconfigurable polarization-rotating unit cell (PRUC) that acts as a wideband 1 bit phase shifter. The unit cell consists of four metallic single-headed arrows placed above a ground plane. The four arrows are connected to the unit cell’s bottom surface, which contains two p-i-n diodes for switching and three lumped inductors for RF–DC isolation. Changing the bias states of the two antiparallel p-i-n diodes reconfigures the unit cell between two operating states that provide a +90° and −90° polarization rotation (PR). Simulation results for the unit cell show a wide frequency range of 8.5–11.5 GHz over which the reconfigurable unit cell provides dominant reflection coefficients of >−2 dB and relative phase shifts of 0° and 180° for the two operating states. The proposed unit cell was used to construct a 256-element, fully electronically reconfigurable reflectarray prototype with aperture dimensions of 192 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times192$ </tex-math></inline-formula> mm to demonstrate the design concept. The digital control circuitry needed to individually control the unit cells was also designed and fabricated. Experimental characterization of the reconfigurable reflectarray demonstrated the 2-D beam scanning capability within the scan range of ±60° over a 30% bandwidth.