Low-Profile Wideband Solar-Cell-Integrated Circularly Polarized CubeSat Antenna for the Internet of Space Things

Abstract

This paper proposes a low-profile wideband circularly polarized (CP) antenna using solar cell patches as radiation elements and a sequentially rotated feeding network for CubeSat applications. To realize a wide axial ratio (AR) bandwidth with a compact size, a sequentially rotated feeding network was designed by modifying a quadrature hybrid coupler and a rat-race coupler that has a small change in phase difference even when the frequency changes. A wideband CP patch array antenna was designed by combining a C-shaped slot-coupled solar cell patch in conjunction with a novel feeding network. The overall size of the proposed CP CubeSat antenna is 100 × 100 × 7.2 mm³ (0.83 λ_o × 0.83 λ_o × 0.06 λ_o at 2.5 GHz). Solar cells occupy 79% of the antenna area, enabling efficient energy harvesting. The –10 dB impedance bandwidth is 1.98–3.0 GHz, which is a fractional bandwidth of approximately 41.0%. The 3-dB AR and 3-dB gain bandwidths are 1.98–3.0 GHz (41.0%) and 1.82–2.98 GHz (46.6%), respectively. The proposed CP solar patch array antenna demonstrates a constant radiation pattern within the –10 dB impedance bandwidth. The proposed CubeSat antenna is suitable for use in an Internet of Space Things (IoST) autonomous communication system.