A projection approach to model the main beam of non-regular arrays in presence of mutual coupling

As a result of mutual coupling, the embedded element patterns of non-regular arrays are all different. It is known that, with the help of Macro Basis Functions, array patterns can be written as a finite series of pattern multiplication problems. However, for the very large arrays envisaged in SKA AA-lo, this still leads to a prohibitive number of calibration coefficients. Two elements may help in this respect: (i) the setting of main lobe and first few sidelobes as a priority for calibration and (ii) the orthogonalization of patterns of MBFs. Examples are shown for arrays of wideband dipoles and of bowtie antennas. The issue of relative shift-independance of the different array factors upon scaning is also analyzed.