Null depth control for downlink adaptive array

Adaptive antenna arrays boost the desired signal and attenuate interference by steering beams and nulls in appropriate directions. Beamforming algorithms find difficulty in simultaneously keeping a zero-dB gain in the direction of the desired user and a deep null in the direction of a close interferer, when these directions are too close (only few degrees apart). The main lobe of the radiation pattern is increased which inflates the required output power for each antenna element and leads to an unwanted increase in interference in other directions. In practical applications, a moderate null depth may be sufficient to control interference. A null depth control technique is addressed in this paper that can prevent this power increase