Joint Features Extraction for Multiple Moving Targets Using (Ultra-)Wideband FMCW Signals in the Presence of Doppler Ambiguity

This article addresses the joint estimation of range, velocity and azimuth for multiple fast-moving targets using (ultra-)wideband (UWB) frequency-modulated continuous-wave (FMCW) radar with a phased array in the presence of Doppler ambiguities. The range migration of moving targets is described with the coupling of the fast-time and slow-time (chirp index), leading to the smearing of the target Doppler spectrum. This phenomenon degrades the performance of conventional detection and estimation techniques.As with range-Doppler processing, the estimation accuracy for direction-of-arrival (DOA) with conventional narrowband-based algorithms significantly degrades if a UWB signal is deployed. For the FMCW waveform, the wideband DOA differs from the narrowband DOA due to an extra coupling term, similar to the range migration problem.A novel spectral norm-based algorithm for joint estimation of range, velocity and DOA of fast-moving targets is proposed, taking the appropriate wideband signal model with the coupling terms into account.The proposed spectral norm-based algorithm avoids off-grid peak search and can be easily accelerated withthe power iteration algorithm; it outperforms conventional coherent integration methods in both accuracy and efficiency when using moderate data size. The advantages of the proposed algorithm and its super-resolution capability are validated withnumerical simulations.