Software Defined Radio for direction-finding in UAV wildlife tracking

Abstract

Two Software Defined Radio (SDR) approaches for assisted wildlife tracking with a multi-rotor Unmanned Aerial Vehicle (UAV) are described. The approaches are Pseudo Doppler (PD) and Yagi Rotation (YR), where each method corresponds to a common Radio Direction-Finding (RDF) technique. Pseudo Doppler utilizes the Doppler Effect by digitally sampling four (or more) monopole antennas in a sequential and circular order, simulating the rotation of a single monopole antenna. This approach can be complex with SDRs and suffers from reduced signal reception from the omnidirectional monopoles. The Yagi Rotation technique utilizes the directional Yagi antenna, rotating 360° about the antenna's center of mass. As the antenna is rotated, the SDR System calculates the Signal to Noise Ratio (SNR) and Angle of Arrival (AoA) of the incoming radio signal. The Yagi Rotation was implemented and field tested; numeric results shown in this paper indicate that system accuracy is limited to the azimuth beamwidth of the Yagi antenna. Due to complexity and reduced signal reception from omnidirectional monopoles, the Pseudo Doppler approach was not implemented; however, a system design is presented. Finally, the SDR methodology and UAV control implications of each approach are discussed in this paper.