Circularly Polarized High Gain Leaky-Wave Antenna for CubeSat Communication

In this work, a novel planar leaky-wave antenna (LWA) and its array are proposed and presented for CubeSat communication applications. Using the substrate-integrated waveguide (SIW) technology, the proposed LWA is implemented by etching periodic fan-shaped slots on top of an SIW. These novel fan-shaped slots exhibit extraordinary circular polarization (CP) radiation in high efficiency over a wide frequency band. Moreover, by switching the excitation ports, both left-handed (LH) and right-handed (RH) CPs are achieved in a wide beam steering range backward or forward. An SIW LWA prototype has been designed and tested with validate LHCP/RHCP steering beams ranging from -51° to 0° or from 51° to 0° in the elevation when the frequency varies from 27.4 to 37.3 GHz. In the 30% frequency band, the axial ratios (ARs) on the main beams are all less than 3 dB demonstrating the broadband CP characteristic. In this 1-D LWA, the realized gain varies from 12.4 to 17.9 dBi. However, it requires higher gain and a fixed beam but narrow bandwidth (BW) in some applications like CubeSats. Hence, a conformal LWA array is further introduced by combining the CP radiation of two LWAs deployed in two perpendicular surfaces of a one cubic unit (1U) CubeSat. Fed by an elaborated vertical transition, the conformal array is designed at 28 GHz with a high directive sum beam along the diagonal direction, requiring each LWA to radiate at ± 45°. As a result, the total gain is enhanced from 14.4 to 16.6 dBi with an AR of 1.8 dB and a sidelobe level (SLL) of -17.1 dB. The proposed compact planar LWA and its array provide promising CP radiation in terms of ARs, BW, polarization flexibility, impedance matching, efficiency, and gain, which reveals great potential for applications in satellite communication systems that demanding low profile, lightweight, dual CPs, and high directivity.