Emerging satellite constellations at low- and medium earth orbits are expected
to revolutionize the expansion of broadband connectivity into rural areas. The
requirements of wide field of view and the availability of larger bandwidths in
the Ka-band have opened new challenges in antenna design. At the same time,
highly cost-effective solutions are needed. The main objective of this thesis is to
investigate and develop quasi-optical millimeter-wave antennas with enhanced
beam scanning and beam reconfiguration capabilities that answer these needs.
High-frequency models are developed for the analysis of different parallel-plate
beamformers in reception. It is shown that these models can be used efficiently
for the design of feed systems with stringent requirements on scanning range.
Two novel lens beamformers, operating in the uplink and downlink Ka-band,
respectively, are presented. The first is a shaped parallel-plate lens combined
with a mechanical scanning feed based on gap waveguide technology. Equivalent circuit models that aid in the design of the feed structure are addressed.
The resulting design and experimental results from an all-metal demonstrator
are presented. The second corresponds to a lens beamformer implemented in
multilayer PCB technology. The developed numerical procedure is applied to
the synthesis of overlapping feed clusters. Both designs represent significant
advances in terms of scanning performance and low-cost implementation
