Time-Varying Angle Estimation of Multiple Unresolved Extended Targets via Monopulse Radar

Phase comparison monopulse technology is a widely used method for obtaining subbeam-level accuracy in angle estimates by processing the complex amplitude ratio of sum-anddifference beams. However, with increases in bandwidth and observation time, the interaction among multiple closely-spaced targets can significantly reduce the accuracy of angle estimates. To address these challenges, this paper proposes a direction-of-arrival (DOA) estimator named 'Classify-Track' for radar operating in long-time coherent integration (LTCI) mode. Initially, we utilize time-varying radial delay features (TRDF) to match unresolved scattering centers across both fast and slow time. Subsequently, we employ the timevarying angle tracking function (TATF) to estimate time-varying angles by searching over slow time and integrating multiple scattering centers. This method, diverging from traditional monopulse techniques, is based on the target motion model and effectively utilizes the angle difference of extended targets at various slow times. Additionally, to reduce computational complexity, we also present a rank-reduced version of TATF (RR-TATF) and provide guidelines for selecting specific hyperparameters within the method. Finally, multiple simulation experiments were conducted using real electromagnetic data from unmanned aerial vehicles (UAVs). The results of these simulations confirm the superior performance of our estimator in various signal-to-noise ratio scenarios.