Low-cost antennas for SatCom on the move systems

Satellite Communication on the Move enables broadband connectivity for mobile platforms. In this context, the expansion of LEO and MEO satellite constellations demands user terminals with better beam agility, reduced weight, and cost-efficiency. Traditional mechanically steered reflectors and phased arrays provide necessary performance but are unsuitable for widespread civilian use due to their complexity and high power consumption. These challenges highlight the need for simpler and lightweight antennas that still meet the required radiation performance standards. A possible solution consists of the use of a primary feed with a reduced number of electronically controlled elements plus a planar or slightly curved meta-lens, located in the near field region of the primary feed and realized with a (quasi-)planar structure, to reduce the antenna system profile. The activity carried out in the thesis was focused on the design and analysis of the fully dielectric, planar meta-lens working in Ka-band and discretized with hexagonally arranged unit cells. Acting as a phase-modulating layer, the metasurface converts the feed’s spherical wavefront into a collimated beam. For this purpose, the use of a hexagonal pattern provides an enhanced surface discretization, promoting a uniform behaviour radially from the structure's center. The use of dielectric materials enables fabrication through additive manufacturing techniques, resulting in a lightweight and mechanically robust structure. Several geometric configurations for the unit cell were designed and then analyzed via full-wave simulations in CST Microwave Studio to quantify scattering parameters and phase control performance. The final geometry consists of a cell with a central hexagonal hole with tapered profile, developed using Preperm ABS1000 material with ε_r = 9.6 and tan⁡δ = 0.2. The structure has a sizeL = 2.2 mm = 0.22 λ_0 at the design frequency f_0=30 GHz and a thickness H = 8.6 mm = 0.86 λ_0. The phase of the incident field can be compensated by varying the dimension of the internal hole diameter d in the range [0.9, 2.1] mm. This configuration delivers a full 360° transmission coefficient phase coverage, while its magnitude is never lower than -3 dB across the Ka-band frequency range (29–31 GHz). Consequently, the unit cell was adopted to design a lens with a diameter D = 100mm = 10λ_0, and illuminated by a circular horn located at a focal distance F = 124 mm from the lens, so that F/D = 1.24. The results of the numerical analysis of this configuration confirm the effectiveness of the proposed lens structure. Considering the need to minimize the volume occupied by the entire antenna, the F/D ratio is reduced to F/D = 0.25. In this case, the lens design must consider that it is in the near-field region of the feed. Additionally, an analysis was conducted to evaluate the impact of relocating the feed from the position employed in the lens design on antenna performance. For its improving, a bifocal lens, engineered to enhance angular coverage and sustain a reliable link with moving satellites, all while minimizing the drop in gain, was also designed and analyzed. This research establishes a strong foundation for advancing satellite communication antenna terminals tailored to new applications in transportation, remote connectivity and autonomous communication systems. Upcoming initiatives will aim to enhance the surface design to ensure conical coverage while minimizing the mechanical complexity within the adopted configuration.