Parameters Estimation of Unresolved Targets with Stepped Frequency Train of LFM Pulses for Phased Array Radar: Range, Angle and Velocity

When multiple targets are located in the same resolution cell, the performance of parameters estimation will get worse greatly. The stepped frequency train of linear frequency modulation (LFM) pulses can provide a high range resolution to separate multiple targets by forming the high range resolution profile (HRRP). But for the phased array radar, HRRP is not available because the range shift caused by targets' angles and velocities, which cannot be compensated in the case of unresolved targets. In this paper, the limitation of HRRP when used on the phased array radar is analyzed. To overcome this problem, the range-angle beamforming technique is used to separate the unresolved targets. However, the peaks of beamformer output still has the range shift caused by target motion. It is found that such range shift is nearly linear to the pulse repetition interval (PRI). So another stepped frequency LFM pulses train with different PRI is transmitted. By combining the target echoes of two pulse trains, the range shift is compensated well besides the ranges, angles and velocities of unresolved targets are estimated accurately. Several simulation results demonstrate the effectiveness of the proposed method.