Pseudo-bearing Measurements for Improved Localization of Radio Sources with Multirotor UAVs

Abstract

Localizing radio frequency (RF) sources is an important application for unmanned aerial vehicles (UAVs), Localization is often carried out by estimating bearing to an RF source, which can be achieved by rotating a directional antenna in place. Multirotor UAVs are well-suited for this sensing modality because they can efficiently rotate in place. However, a full rotation from a single location is needed to account for scale factors affecting the directional antenna's measurements. Although easy to perform, these rotations tend to be slow and delay localization. In this paper, we equip a multirotor UAV with a directional antenna and an omnidirectional antenna. The omnidirectional antenna serves to normalize measurements made by the directional antenna, yielding “pseudo-bearing” measurements. These bearing-like measurements are less informative than bearing measurements but do not require a full rotation, leading to more measurements and faster localization. We validate the normalization with antenna theory and ground tests. Claims of improved localization are validated with simulations and flight tests on a multirotor UAV. Our setup significantly reduces localization time compared to a multirotor UAV equipped with only a directional antenna.