New sets of constraints for maximally flat optimum broadband antenna arrays

A method frequently employed to optimise the performance of a broadband antenna array processor is to find the set of processor weights which minimises its mean output power subject to linear constraints on the processor weights. These linear constraints determine the frequency response of the array processor in the look direction. To obtain robustness against mismatch between the array look direction and the actual signal direction, derivative constraints can be further imposed. However, derivative constraints corresponding to necessary and sufficient (NS) conditions for a maximally flat spatial power response in the look direction are in general quadratic. This limits their value for real-time processing. This paper presents several simpler derivative constraints. These constraints correspond only to sufficient conditions for maximal flatness but perform almost as well as the NS constraints and are better suited to real-time implementation