Wideband high-gain beam-steerable reflectarray for millimeter-wave non-terrestrial networks

Abstract This paper presents a wideband, high-gain, beam-steerable reflectarray antenna designed for Ka-band non-terrestrial network (NTN) applications. The antenna consists of a 31 × 31 planar array of sub-wavelength metallic square ring unit cells, whose geometric dimensions are discretely varied to realize eight distinct phase states, thereby implementing a 3-bit quantized phase modulation scheme. The reflectarray is illuminated by a wideband horn antenna, which is mechanically rotated to enable beam steering operation. At 28 GHz, the proposed design achieves a peak gain of 27.8 dBi, a beam-switching loss of 1.9 dB, an aperture efficiency of 55.4%, and a 3 dB gain bandwidth of 46.78%. The reflectarray and horn antenna were fabricated using printed circuit board (PCB) and 3D printing technologies, respectively, and the assembled prototype demonstrates good agreement between simulation and measurement, confirming the suitability of the design for mm-wave NTN applications.