Methods and Experiments for Forward Scattering Detection of UAV Targets Based on Opportunistic Illumination from Low-Orbit Satellites

‍ ‍Owing to advancements in unmanned aerial vehicle （UAV） technology， the demand for the efficient monitoring of typical “low， slow， small” target UAVs has increased. Given the difficulties in UAV detection， this study proposed a new type of UAV low-altitude detection method using low-orbit satellites as the source of opportunity illumination， combining the miniaturization of the forward scattering system， anti-stealth， and the all-weather and easy-to-acquire characteristics of satellite signals， and investigated the potential applications of the satellite signal forward scattering radar for UAV detection. First， this study analyzed the geometric structure of the satellite signal forward scattering radar， introduced the signal processing flow of the forward scattering radar， constructed the radar evaluation model based on the horizontal baseline distance of the target， and simulated the maximum horizontal baseline distance that can be detected by the radar under the different target flight heights. The simulation result showed that when the flight altitude of the UAV was 100 m， the maximum horizontal baseline distance detected by the radar was 77.2 m. Modeling analysis of the satellite motion and antenna beamform on the time-frequency characteristics of the UAV target was conducted. The analysis results showed that the motion of LEO satellites had less influence on the time-frequency characteristics； when the antenna beam was too narrow， the time-frequency response changed from a “V”-shaped image to a “vertical bar” image. A low-orbit satellite signal-receiving system was also designed according to the characteristics of high-speed movement of low-orbit satellites， and system test experiments were conducted， and the results of the test experiments showed that the designed system received low-orbit satellite signals in a stable manner and in real time. Finally， the low-orbit satellite forward scattering radar UAV detection experiment was conducted， and the time-frequency characteristics of the forward scattering when the drone crosses the baseline were obtained； the experimental results matched the simulation results， proving the accuracy of the theoretical analysis and the feasibility of detecting the UAV target using the proposed system.