ETD

• 5G
• antenna arrays
• array design
• beamforming
• formation of arrays
• formation thinning
• geostationary earth orbit
• low earth orbit
• mega-constellations
• non-terrestrial network integration
• phased arrays
• power
• satellite antennas
• satellite communications
• throughput

Effective integration of terrestrial and non-terrestrial segments is one of the key research avenues in the design of current and future wireless communication networks. To this aim, modern communication-satellite constellations intend to attain sufficiently high throughput in terms of bit rate per unit area on the ground by rather aggressive patterns of spatial frequency reuse. This goal calls for on-board narrow-beam antennas, whose size turns out to be in many cases incompatible with the size/mass and accommodation constraints of the hosting satellite. This thesis investigates the attainable performance of large distributed arrays of antennas implemented as the ensemble of a few to many simpler sub-antennas of smaller sizes, carried by one (small) satellite each. The sub-antennas can in their turn be implemented like (regular) 2D arrays of simple radiating elements, realizing an overall (distributed) antenna architecture that we call “Formation of Arrays” (FoA). The satellites that implement this radiating architecture need to be relatively close to each other and constitute a formation of flying objects, to be coordinated and controlled as a whole. In this thesis, there is a theoretical analysis of a FoA antenna, and how to take advantage of this new technology to improve network throughput in a multi-beam S-band mobile communication network with low-earth or geostationary orbiting satellites directly providing 5G-like communication services to hand-held user terminals.
The FoA distributed antenna technology has recently been proposed to provide 5G-like mobile satellites services in the context of the integration of non terrestrial with terrestrial networks – the overall system goal being a sufficiently high throughput in terms of bit rate per unit area on the ground. This large distributed array configuration must be carefully engineered to provide the desired benefits. In this thesis, we also tackle some fundamental issues related to FoA design, namely, frequency selectivity, power generation, and optimal formation configuration. Concerning frequency selectivity, we evaluate the intrinsic FoA frequency response assuming a wideband signal, and suggest how to mitigate possible impairments from a communication system perspective. Regarding power generation, we show how to decouple the functions of antenna and solar arrays to come to a power-efficient satellite configuration and design. Finally, in terms of formation optimization, we investigate a formation thinning approach with random placement of satellites on a grid, leading to a significant reduction of secondary beams in the emission of the FoA as well as fully satisfying the constraints placed by optimum power generation.