A Novel Scheme for Detection and Estimation of Unresolved Targets With Stepped-Frequency Waveform

The “masking effect” of unresolved targets always results in missed detection and inaccurate parameter estimation. A feasible approach to separate the unresolved targets is improving the range resolution by increasing the signal bandwidth. In this paper, we propose a novel scheme to detect and measure the unresolved targets for the phased array radar with stepped-frequency waveform, which provides a large synthetic bandwidth. We establish the signal model of the stepped-frequency pulse train and review the conventional 1-D High Range Resolution Profile (HRRP). Since the 1-D HRRP of each element fails to integrate the spatial domain, we develop a 2-D HRRP where the target echo can be effectively integrated both in time and spatial domains. Specifically, the 2-D HRRP is generated by the range-angle beamforming technique. In order to address the range shift in the 2-D HRRP caused by target motion, we design a short-long stepped-frequency pulse train as the transmit waveform, which contains a short pulse subtrain with a small pulse repetition interval (PRI) and a long pulse subtrain with a large PRI. The proposed scheme includes two parts of beamforming detection and parameter estimation with range shift elimination. Based on two 2-D HRRPs generated by short and long pulse subtrains, each target can be successfully detected by beamforming detection and target's range, angle and velocity can be accurately estimated by parameter estimation with range shift elimination. Simulation results demonstrate the effectiveness of the proposed scheme.