C-band aircraft-to-ground (A2G) radio channel measurement for unmanned aircraft systems

This paper presents a summary of a measurement campaign on radio propagation channels in air-to-ground (A2G) links based on a usage scenario of unmanned aircraft services (UASs). In order to reveal their propagation characteristics, a measurement setup has been established that transmits a designed FMCW signal continuously from a small manned airplane with frequency bandwidth of 20 MHz at center frequency of 5060 MHz, and records the transmitted signals on ground as IQ waveforms by using a vector signal analyzer. Metrics on radio propagation characteristics including received signal strength (RSS) and channel impulse responses (CIRs) are obtained from the recorded data. The results on obtained RSS have shown that the trends of RSS change in the A2G links is expressed by free-space pathloss with a shadowing component encountered in mobile radio communications. Regarding the CIR in A2G links, it is observed that the radio propagation channels are expressed by a direct path and a ground reflection with scatter components; however, the direct path has margin of more than 20 dB in signal level against the other components.