Flight Test Performance of an RFSoC Based Direct RF FMCW Radio Altimeter

The radar altimeter (RA) is one of the most important sensors in avionics systems. It is the only sensor that reliably indicates altitude above the ground. With the roll-out of the 5G network, many concerns have been raised about the interference between the 5G network and radar altimeters. This issue highlights the importance of future-proofing avionics systems. One way to do this is by leveraging software-defined radio (SDR) technology. Advances in high-speed analogue-to-digital converters (ADCs) and digital-to-analogue converters (DACs) have made it possible to directly digitise the radio frequency (RF) signal and get rid of the RF mixing stage. This is called Direct RF Sampling (DRFS). This work aims to demonstrate the feasibility, capability, and performance of a DRFS radar altimeter based on the Xilinx RFSoC technology. The radar altimeter was tested in a laboratory environment and in a flight test. The laboratory test results show that the radar altimeter meets the MOPS tolerances. The flight test results show that the prototype is accurate at altitudes above $\mathbf{5 0 0} \mathbf{f t}$ but there are still some issues that need to be addressed. The results show that DRFS is a viable solution for high bandwidth systems like the radar altimeter.