Antenna tracking techniques for long range air-to-ground communication systems using a monopulse method

In this paper, we consider long range air-to-ground (AG) communication systems which support airborne platforms including unmanned aerial vehicles (UAVs) for real-time applications. In this system, we design tracking techniques for directional ground antennas which enable reliable AG communication regardless of dynamic maneuvers of the UAV. We apply a simple monopulse method and a fixed gain filtering algorithm to develop a single channel monopulse tracking system with an angular estimation filtering, which exploits a downlink signal without requiring a dedicated channel. Through the AG communication prototype and realistic flight tests, we evaluate the tracking accuracy performance at the distance of hundreds of kilometers and demonstrate the auto-tracking capability of the angular estimation filter. The flight test results show that the tracking accuracy of our proposed system is sufficient for long range transmission with a narrow beam antenna. Also, in the absence of the downlink signal, it is observed that the ground prototype can resume the monopulse tracking procedure, and successfully maintains the tracking accuracy.