Adaptive clutter suppression for airborne array radars using clutter subspace approximation

The main problem is that the moving target echo is submerged in Doppler broadened sidelobe clutter in the frequency domain so that purely temporal filters cannot suppress the sidelobe clutter with the same Doppler frequency as the moving target. However, because the sidelobe clutter comes from different direction from that of the target, the moving target echo can be distinguished from the sidelobe clutter in space domain and from the mainlobe clutter in time (frequency) domain, optimum clutter suppression can be performed by a filter operating on both time and space. The space-time filter requires space-time sampling of the echo field. It can be realized by a coherent pulse Doppler radar with an array antenna. The sensor elements of the array provide spatial samples, and the coherent pulse train realizes temporal sampling of the echo field