High gain X-band space antenna capable of beamsteering

Small satellites orbiting in low-Earth orbits enable new applications requiring the transfer of information between the satellites and ground stations. However, such a system demands both a substantial signal-to-noise ratio at the receiver and broad system bandwidth to have good data throughput. Therefore, the goal of this master thesis is to study a high gain X-band beamsteering-capable space antenna to improve the system signal-to-noise ratio. Furthermore, the system scan requirement is broad to maximize the link availability duration. This work is a collaboration with Aerospacelab, active in geospatial intelligence. Worst-case analysis of the link budget sets the requirements to close the link and predicts the achievable spectral efficiency. It fixes a minimum directivity of 10.2 dBi for the antenna. We studied conformal phased array antennas to accommodate the high scan requirement. Nevertheless, planar phased arrays maximize the performance for this application while limiting the manufacturing complexity. Selecting the beamformers and power dividers sets the minimum radio-frequency input power (0.048 W) and DC supply power (28.8 W) for the antenna. We made a first layout proposal based on several considerations. Finally, we designed an aperture-coupled antenna with a specific microstrip-to-stripline transition to avoid using blind vias. It has a 6.4% impedance bandwidth and linear polarization. Sequential rotation of the antennas in a two-by-two array improves the axial ratio of the system, which targets a circular polarization. This microstrip-to-stripline transition through coupling enables feeding the antennas without requiring blind vias. In an environment like space where significant thermal expansion provokes mechanical stress on the structure, such a transition is of interest as it improves the system's robustness.