Design and Analysis of New Surface Wave Antennas for CubeSat and Other Small Satellites

Abstract

The rise of small satellites, particularly CubeSats, has brought about the demand for innovative antenna solutions and compact circuit designs offering high performance at a low cost. Although these small satellites cannot fully replace traditional systems, they are reshaping the future landscape of space satellites. Technological advancements, including digital signal processing, micro-electromechanical systems, low-power programmable systems, integrated circuits, and miniaturisation, have enabled these satellites to efficiently handle increasingly complex tasks despite their small size. However, designing antennas for CubeSats poses distinct challenges, primarily related to size, weight, and power limitations, making it a crucial yet intricate aspect of these miniature satellite systems.

Researchers have explored innovative techniques such as integrating non-deployable antennas with solar panels on CubeSats, creating additional space for solar cells, sensors, and communication devices. While many SmallSat antennas radiate signals broadly, the direction in which these signals travel may not always align with the intended orientation of the CubeSat and in the required direction. For example, endfire antennas radiate electromagnetic fields precisely in the longitudinal direction of the antenna structure, making them potentially more suitable for CubeSat applications. These types of antennas can also offer a low aerodynamic drag profile, especially when compared to some broadside antennas, making them advantageous for other related practical scenarios such as on airplanes and cars.

In this thesis, the primary objective is to bridge the gap in high-gain antennas integrated with solar cells, particularly for high-frequency and endfire radiation applications. The focus is on possible techniques for integrating the solar panel aperture with the antenna to minimise space requirements on the CubeSat platform. Innovative planar configurations are introduced as efficient and low-profile antenna solutions for CubeSats and other Small Satellites, employing advanced concepts like substrate integrated waveguide (SIW) technology, surface wave (SW), and leaky wave (LW) principles. The first approach involves a leaky SIW T-junction for compact feeding, creating a uniform wavefront in a truncated parallel plate waveguide (PPW) section. This leads to the development of a planar quasi-endfire surface wave antenna (SWA) utilising the fundamental TM0 SW mode at the edge of a grounded dielectric slab (GDS). To enhance performance, a sub-wavelength matching section (SMS) is added to ensure a smooth transition between the PPW and GDS, improving antenna radiation characteristics. The measured prototype demonstrated realised gain values of 13.3 dBi at 18.6 GHz for a competitive structure size of 5λ0 * 4.8λ0 and with a simulated total radiation efficiency of 93.4%. The second approach focuses on achieving a truly endfire high gain antenna designed for 3U CubeSats. This design incorporates an air vias (AV) section and a dual-layer structure based on the distributed aperture principle. In the design, the transverse equivalent network (TEN) was applied and results are supported by the theoretical framework and the developed equations. This experimentally demonstrated antenna is fed by two leaky SIW T-junctions with a 180° phase shift between them and a common ground plane and an AV section with a fixed diameter to modify the relative permittivity. This enabled full, endfire radiation and the possibility to integrate solar cells. The measured prototype established a peak realised gain of 17.5 dBi at 18.6 GHz and with high radiation efficiency and low sidelobe levels. Lastly, an endfire high-gain antenna suitable for 1U CubeSats was also developed. This design employs an ungrounded substrate featuring AV sections with varying diameters, facilitating a gradual change in permittivity for minimal reflections to the air region. To feed this ungrounded substrate, a series of SIW horn antennas operating in phase are utilised in an array, ensuring optimal radiation performance and simple feeding. Simulation results show a directive endfire pattern with a directivity of 21.3 dBi at 24 GHz.