Classification of helicopter Doppler ambiguous echo signal

One of the tasks performed by contemporary radars is the classification of a type of detected objects. Among many types of objects, helicopters, and especially hovering ones, are of special interest in radar's self-defence. The echo signal of such object possesses specific properties of its spectrum that result from the construction of the object. A characteristic property of the echo signal is the presence of the spectral components from the hull of the helicopter as well as from the main rotor. The parameters of the latter components depend on the rotary speed of the rotor, the number of the blades and their length.