A Passive Broadband Radar System Design for Low, Slow and Small Target Detection

This paper designs multiple targets passive radar system that can estimate the position and velocity information using orthogonal frequency division multiplexing (OFDM) signal emitted from an uncooperative fixed transmitter. The radar receiver has two channels. In channel one, a high gain directional antenna points to the transmitter to obtain a pure reference signal. The other part is configured with a uniformly rectangular array (URA) to capture the multi-target echo signals. As the echo signals scattering back from small targets with lower RCS are weak, a long correlation operation of the echo signal with the reference signal is required to detect the targets, unfortunately, which will degrade by the frequency shift arising from the movement of targets. This paper uses a piecewise correlation accumulation algorithm to solve this problem. First, we obtain the relative delay profile of the echo signal by a piecewise correlation between it and the reference signal, followed by the nonlinear accumulation of block and multiple receiving channels. Then, a detection procedure is applied to discriminate the targets. The direction of the target relative to the URA can be estimated by 2D DOA algorithms using the block-correlation array signal sampling at the target relative delay. Using the beamformed multi-channel echo signals, we can estimate the target Doppler by the Root-Music algorithm. Finally, we can estimate the targets ‘ location and velocity from the geometric relationship between the transmitter, receiver, and target with the obtained delay, direction, and Doppler parameters. Simulation results verify the feasibility of our designed passive radar system.