Nowadays, civilian applications including air surveillance, remote sensing, law enforcement, etc. can be implemented by means of remotely controlled, unmanned aerial vehicles. These aircraft are commonly called UAVs. They are usually controlled and operated from distant locations using low frequencies (VHF, UHF) guarantying a sufficient maximal range and supporting low data rates for telecontrol and telemetry. However, for high data rates, another, higher frequency link is required. This link is used to send back to base the images (SAR, radiometer, …), sensor data, or any other information gathered during normal operation, as on-board storage would increase the payload weight and because real-time data processing may be needed, not feasible onboard. The frequencies of interest are in the UHF range where diffraction, reflection and multipath effects dominate. Representative measurements have been performed at 2 GHz.
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