Antenna Elements and Arrays for Future MEO/LEO Navigation Terminals

Kurzfassung

In this thesis, multi-band antennas are investigated to cover both the L-band and the C-band. These elements and arrays are arranged in a dual-band antenna system for L-band and C-band. Such multi-band antennas provide for future satellite navigation terminals combining L-band reception from MEO satellites with C-band reception from LEO satellites. The designed dual-band antenna system consists of a cylindrical-hemispherical dielectric resonator antenna with embedded square prism elements, which are arranged in a two by two array configuration. While the larger cylindrical-hemispherical element provides a broad beam width for the upper hemisphere, the smaller square prism elements exhibit a strongly directive pattern. These narrow beam widths of the square prism elements are designed for future C-band capabilities in GNSS. The outer structure of the much larger cylindrical-hemispherical element is used as a lens for passive beam forming the radiation patterns of the single C-band elements. Two different types of feed networks are investigated. The pin feed presents excellent coupling for the cylindrical-hemispherical dielectric resonator antenna, while deteriorating the performance of the square prism dielectric resonator antenna array in the C-band. Conversely, the slot feed provides insufficient coupling to the cylindrical-hemispherical element, decreasing the performance in the L-band, while it does not interfere with the C-band performance. Clearly, a trade off between the feed types should be considered. An additional anti-reflection layer surrounding the cylindrical-hemispherical element is implemented for both feed types to improve the C-band performance of the square prism dielectric resonator antenna array elements. The designed antennas have been optimized and then manufactured and tested. Best performance is achieved during measurement of the antennas with slot feed. The antireflection layer displays a better performance for both feed types in terms of beamwidth, matching and polarization purity.