Nearfield spot-beamforming with distributed arrays

The concept of spot-beamforming with distributed arrays (DAs) is introduced. DAs are array-source configurations whose array elements are spatially dispersed submerging the sources in the nearfield of the array, where they can be distinguished not only by their angular but also by their range signature. The resulting enhanced spatial discrimination capabilities reflected in a beampattern characterized by spot-like mainlobes lend DAs optimality properties. A gradient based algorithm for the joint optimization of the array geometry and the shading coefficients of a narrowband spot-beamformer in a stationary multiple source system is derived, and its convergence and performance are discussed. An important subclass of DAs, namely distributed linear arrays are introduced. This class is of practical significance and has the important property of being; ambiguity-free in the limit for high SNR. For DAs with an arbitrary geometry, which can suffer from spatial aliasing, a set description of the ambiguities is given.