Design and Development of a Helical Antenna for Mitigation and Characterization of Multipath

Multipath remains one of the most significant challenges in GNSS positioning in urban environments. This study will present the design and development of a helical antenna aimed at both mitigating and characterizing reflected signals using real-world collected data. The antenna design is optimized for directivity while still allowing for observations of lower-elevation satellites. The antenna successfully acquires strong GNSS signals and it is possible to use it for computing a position. To explore the capabilities of the custom-made helical antenna, three applications have been explored: (1) pointing the antenna upwards to minimize ground reflections, (2) using multiple antennas at different azimuths to distinguish direct and reflected signals, and (3) leveraging a Left-Hand Circular Polarization (LHCP) antenna to possibly analyze reflections from known surfaces. Experiment (1) shows that the helical antenna does reduce some multipath errors, however likely due to the low-grade quality of the antenna, a worse positioning accuracy is seen. Experiment (2) shows a large improvement in positioning, as the reflected signals are ignored by the antennas, due to arriving outside of the main lobe. Experiment (3) showcases the possibility of capturing LHCP signals with the custom helical antenna. These experiments suggest that the helical antenna is a versatile tool for multipath-related studies, although further refinement is needed to improve its overall performance.