Infoscience

Thesis

Antennas for low-cost Ka-band ground terminal devices

The ever-growing demand for high-speed data links together with the increasing congestion in the traditional microwave spectrum are pushing for the exploitation of higher microwave and millimeter-wave (mm-wave) frequencies, including the so-called Ka band. Major investments came along, especially in the satellite communications industry, raising the technological con-straints imposed on electronic equipment, mainly concerning performance, compactness and both reduced cost and weight. The great antenna size reduction achieved at Ka band has boosted the research towards satel-lite-on-the-move applications (SOTM), aiming the development of ground terminal antennas for both commercial and personal use. Such antennas must work simultaneously at downlink and uplink Ka bands with circular polarization and also have beam steering capabilities to keep a steady connection with the satellite. In addition, the target is also achieving a cost-effective low-profile antenna. The present thesis is focused on the design of feed antennas to be integrated in mechanical beam steering systems for the aforementioned application. Three different designs are here proposed and discussed. The first one, a wideband ridged horn antenna, was tested standalone and with a dielectric lens antenna. Once good results were achieved in both sce-narios, reducing its height would be the next goal. Thus, the second design is a cavity backed patch antenna. A comparison between both feed antennas is performed, highlighting the pros and cons of both solutions, either standalone or with the same dielectric lens antenna. Here, the first studies with a planar lens antenna are shown. Finally, the third device consists of a ridged cavity antenna with a cross-slot on its top aperture. This time, the feed was successful-ly tested with a transmitarray which allows achieving a more compact antenna system than the first one here presented. This thesis also analyzes two different manufacturing techniques, traditional milling technique and an innovative additive manufacturing (AM) technique based on metallized polymers called stereolithography (SLA). The present AM-SLA prototypes clearly illustrate the strong potential of this technology and pushes for its further assessment.

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