Onboard Antenna Placement Studies for CNPC Links of UAS Using AeroMACS

Recently, much attention has been paid to unmanned aircraft systems (UAS), especially for civilian purposes such as disaster prevention and transportation. This paper considers big long-flight-type UASs remotely piloted from ground station by radio communication link, since these types of UASs require higher reliability. The purpose of this paper is to consider a communication system which transmits real-time video of the surroundings of aircraft from unmanned aircraft to the ground pilot. In this paper, the aeronautical mobile airport communications system (AeroMACS) is considered as a command and non-payload communications (CNPC) link between unmanned aircraft and ground pilot. Flight tests using the experimental aircraft and AeroMACS prototype system are conducted to obtain the air-to-ground propagation profile. In addition, the placements of airborne antennas are considered, because the positional relationship between airborne antenna and ground fixed antenna is not constant during the flight. The results of flight tests show the effectiveness of our system, and the received signal strength indicator (RSSI) obtained by flight tests has the same tendency as the free space propagation model. Finally, the results of flight tests show that a vertical placement on top and bottom of aircraft body is effective for the multiple inputs and multiple outputs (MIMO) antenna configuration of UAS.