Adaptive antenna nulling for a phased array monopulse radar

In monopulse tracking systems using adaptive arrays, two adaptive receiving beams are formed: a sum beam, Σ, and a difference beam, Δ. It is desired that adaptation in both beams allows the nulling of external interference sources, a low loss for the desired signal in the Σ beam and the derivation of a monopulse error signal which indicates the angle of arrival of the desired signal. The author presents an approach to derive adapted Σ and Δ beams. The Frost (1972) power minimization criterion is selected as the adaptive nulling technique along with appropriate main-beam constraints for the Σ and Δ beams. This combination is shown to result in the required nulling of the interferers, a low signal loss and a monopulse error characteristic free of any boresight bias. A variation of this technique is shown to yield the desired quiescent patterns