Angle of Arrival Estimation in the Presence of Phase Difference Ambiguities

For a variety of applications, the task of global localization is to determine both, the position and the orientation of one or more mobile objects. An important area of application is mobile robotics, where knowledge of the heading angle is of great importance. One way to localize a mobile robot in real time is to use a network consisting of IEEE 802.15.4a radio nodes based on Ultra-wideband (UWB) technology. In addition to measuring the signal propagation time, UWB radio nodes equipped with multiple transceiver modules can also estimate the Angle of Arrival (AoA) of the signal by capturing the phase differences. The additional angle information can be used to increase location accuracy and reduce the absolute number of radio nodes required in a deployment environment. For this reason, this paper investigates the feasibility of AoA estimation based on UWB radio nodes. Specifically, radio nodes from Nanotron Technologies/Inpixon based on the swarm bee ER module are employed. One problem of the specific circuit board design used is that the antenna spacing is so large that ambiguities occur when detecting the phase differences, which leads to large AoA estimation errors. Hence, methods for solving this problem are presented and their functionality is evaluated based on real world measurements.