A compact tri-band omnidirectional antenna design for CubeSat applications.

This paper presents a compact tri-band omnidirectional antenna designed for CubeSat applications, operating at UHF (0.755 GHz), L-band (1.25 GHz), and S-band (2.28-3.74 GHz). The antenna features a defected ground structure (DGS) and metallic vias, which enhance impedance matching and enable stable multi-band resonance while maintaining a small footprint of 0.26λ × 0.26λ × 0.013λ within a 1U CubeSat. Unlike conventional CubeSat antennas that require external deployment, the proposed design is fully enclosed within the CubeSat, ensuring easy integration and mechanical robustness. The antenna exhibits omnidirectional radiation patterns across all frequency bands, making it suitable for reliable satellite-ground communication. The measured results confirm a high radiation efficiency exceeding 90%, and strong agreement between simulated and experimental results. The combination of compact size, multi-band operation, and high efficiency makes this antenna an ideal candidate for next-generation CubeSat communication systems.