3-D Coupled Annular Aperture Antenna Array With Dual Circularly Polarized Isoflux Beam for CubeSat Earth Coverage Applications

This communication introduces the concept of coupled annular aperture antenna array (CAAAA) that enhances Cube Satellite (CubeSat) Earth coverage with dual-CP isoflux beams. Unlike the formerly reported annular aperture antenna array (AAAA), which relies on complex feeding networks with numerous excitation ports for amplitude and phase adjustment, the CAAAA simplifies design and reduces radiation losses by optimizing the 3-D spatial arrangement, thus tailoring excitation parameters of passive coupled annular aperture elements (coupled AAE) encircling a central excitation annular aperture element (excitation AAE). The inherent axisymmetric structure of the CAAAA yields a consistent axisymmetric radiation pattern. A C-band (5 GHz) prototype demonstrates ±30° isoflux coverage, 4.5-dBi peak gain, and an axial ratio (AR) beamwidth exceeding 180°, indicating robust dual-CP performance. Notable for its low profile ( $0.11\lambda _{0}$ ), lightweight design, ease of fabrication, and high radiation efficiency, the CAAAA offers a viable, efficient solution for CubeSat applications requiring extensive Earth coverage.