Monopulse estimation with subarray output adaptive beamforming and low sidelobe sum and difference beams

Monopulse estimation with adapted sum and difference beams can produce a large bias, because the shape of the beams can be severely distorted by the nulls formed in the jammer directions. This effect is distinct for mainbeam jammers. With an adaptive array that uses the subarray outputs one can, in principle, correct this bias. The previously developed correction formula for element adaptive arrays are generalized to subarray output arrays with arbitrary sum and difference patterns, e.g., for patterns with low sidelobes. We assume that a low sidelobe sum beam is formed by element tapering and low sidelobe difference beams are formed by subarray output weighting. The bias can be further reduced by switching the beams at the subarray level to the estimated direction and repeating the procedure. This is called the multistep monopulse procedure