Robust low-angle tracking by beamforming

One of the agents of error in angle of arrival estimation of signal is the response of the ground to the reflected waves from the target. In low-height target situations this phenomenon can be so tormenting that may cause much more error than thermal noise. In this article two methods of Fixed Beam and Double Null are used as preliminary techniques to overcome the problem of low-altitude targets angle estimation and the optimum weights for beam-forming array radar are proposed. The beam-forming methods enable the radar to estimate the target angle precisely while it is robust against diffuse and specular ground reflection components and the exact knowledge of surface slope is not required.