Tethered UAV with High Gain Antenna for BVLOS CNPC: A Practical Design for Widespread Use

This paper presents the design of a hovering, tethered unmanned aerial vehicle (UAV) capable of lifting a high gain antenna which can be used as a relay node for Control and Non-Payload Communications (CNPC) from a ground control station to a distant UAV. Ground based remote controllers are constrained by the terrain and the curvature of the Earth. The proposed design overcomes these limitations and provides a tower alternative, which is inexpensive, easily deployable, and moveable in all three dimensions. We show that a typical battery-powered UAV flight time is limited to just above one hour, or under half an hour with its maximum liftable payload, and therefore propose a power tether that connects the UAV to a ground power source. This is important to be able to serve rover UAVs that can be asynchronously launched. The hovering UAV will turn to steer the high gain antenna based on position reports from the roving UAV. The prototype design leverages commercial off the shelf equipment as much as possible and uses the L-band unlicensed frequency range of 902-928 MHz which is close to the aviation protected frequency band.