A Flexible K-Band FMCW Radar Prototype for Low-RCS Nano-Drone Detection

Nano-drones are insect-like drones used to provide intelligence through their capability of intrusion and ability to carry small sensors. They pose a defence and security threat and can potentially violate secure establishments and privacy rights. Their rapid emergence and increased availability have made them an existing technology which is affordable and easy to operate. Nano-drones are typically defined as drones smaller than 15 cm. They are light and stealthy in nature and present a very low radar cross-section (RCS) which creates a significant challenge for active Radio Frequency (RF) security systems tasked with detecting potential threats. This paper presents a K-band Frequency Modulated Continuous Wave (FMCW) radar prototype tailored for detecting nano-drones. Operating at 24 GHz and utilising commercial off-the-shelf components, the radar offers a low-cost, flexible and customisable solution with user-selectable frequency and waveform parameters. The system's detection capabilities were tested using low-RCS oscillating metallic spheres ranging from 0.5 to 3.0 cm in diameter. Nano-drone detection was demonstrated using range-Doppler maps and time-frequency spectrograms of a real and small 5 cm nano-drone. The paper provides a detailed overview of the radar design and test methodology, together with a detailed investigation of the radar performance.