Main beam jammer cancellation and target angle estimation with a polarization-agile monopulse antenna

An alternative, more cost-effective approach to cancellation and angle estimation in airborne radars is proposed. A set of preformed, phase-steered, product-pattern monopulse beams are used to form adapted sum (Σ) and difference (Δ) beams that yield undistorted target monopulse ratio estimates while nulling both main-beam and sidelobe ECM (electronic countermeasures). The authors consider three approaches to optimal weight calculation. The first is a straightforward sample-matrix-inversion algorithm, which maximizes the signal-to-noise ratio in a prespecified look direction or, equivalently, minimizes the adapted beam residue subject to a unity-gain constraint in the prespecified look direction. The other two approaches to adaptive weight optimization are based on finding the eigenvector with the minimum eigenvalue for modified versions of R (the sample covariance matrix). Results of algorithm performance analysis are presented. The bandwidth effects of phase-steered antennas on the main beam canceller are also discussed