Development of structures capable to minimize the sensitivity of GNSS antennas from their mounting platform

Abstract

Global navigation satellite systems (GNSS) offer worldwide information in terms of positioning, navigation and timing (PNT) for multiple applications. Especially applications such as geodesy and reference stations, have strong requirements on the GNSS positioning accuracy. However, the achievable accuracy at the GNSS receiver is limited by the frequency and direction dependent properties of the antenna, which introduces an antenna-induced error in the GNSS measurement. To compensate these effects, commonly high precision GNSS antennas are calibrated. Nevertheless, research in the recent years has shown that the calibration data is no longer correct when the objects in the antenna vicinity are not the same as during the calibration procedure. This concerns all objects in the antenna near-field, such as the required antenna mountings and adapters. This thesis aims to design a structure, which reduces the influence of the antenna mountings on the pattern, making the antenna effectively more insensitivity to changes of the objects in its vicinity. To achieve this, an approach using tapered resistive sheets to be place on the antenna ground plane has been chosen. The optimal structure is then found by means of optimization of a cost function, that considers the pattern variations on the different mounting structures and aims to minimizing them. The simulated optimal structure has then been produced by means of additive manufacturing (AM), after having analyzed how to obtain the required material parameter to be printed from the required surface resistivity values. Simulation results have demonstrated the functionality of the structure. However, in measurement, the expected results could not yet be replicated, due to further implementation-related issues that arose at measurement time. Possible countermeasures and next steps are discussed in the thesis.