CFAR coherent radar detection against K-distributed clutter plus thermal noise

The paper shows the non-CFAR characteristic of the asymptotically optimum detector (AOD), when applied to a mixture of K-distributed clutter plus thermal noise, as the target Doppler frequency is varied. The upper bound to the performance against such composite disturbance is investigated by considering an ideal-AOD detector, which assumes a knowledge of the local clutter power in the cell under test. A practical scheme is obtained by replacing the known local power value with its estimate. The resulting detection scheme, named locally adaptive-AOD (LA-AOD) shows a proper CFAR characteristic, but yields strong detection losses in the same Doppler frequency region where the original AOD operates effectively with CFAR. Finally, a combined detector, Comb-AOD, is proposed, which uses the benefits of both the AOD and LA-AOD structures, and its detection performance is fully characterized as the clutter spikiness and correlation vary.