Some new studies of angular resolution for linear arrays

This paper studies the limitation on the angular resolving power of linear aerial arrays. It is shown that there are some fundamental differences between the resolving powers of arrays, depending upon whether they are mechanically rotated or undergo electronic beamscanning and this leads to a new approach to superdirectivity for arrays employing continuous mechanical rotation. It is shown that a superdirective array can be used with electronic scanning but this process requires discontinuous changes in the array excitation. The ultimate resolving power of a fixed linear array in the absence of noise is studied in terms of its ability to determine separately the angular location of a number of point sources. It is shown that the maximum number of such sources that can be independently located by an n-element array is given by (n¿1). It is further shown that the use of multiplicative signal processing or any other form of non-linear processing on the output of the array can produce no improvement over this limit. The change in the resolving power of arrays from the noise-free case to the noise-limited case is also discussed.