Approach with nonuniform linear arrays

Until now, we have dealt with ULAs but another straightforward geometry extension is the nonuniform linear array (NULA), which is the focus of this chapter. First, we show how from two virtual ULAs we can construct a physical NULA whose associated steering vector is the Kronecker product of the steering vectors associated with the virtual arrays. Then, we explain how Kronecker product beamforming is performed. We give the most important performance measures in this context. Finally, we show how to derive some interesting optimal beamformers.