Improvement of the GO/PO method for the study of focal array fed lens antennas

Focal array fed lens antennas are very attractive for multi-beam and beam shaping applications at millimetre waves. They typically consist of an integrated lens antenna illuminated by phased sub-arrays. Due to their moderate or even large size, their radiation characteristics are generally computed using high-frequency techniques like the geometrical optics/physical optics (GO/PO) method. We introduce here a refined version of the conventional GO/PO algorithm in order to account for mutual coupling between the elements of the feed sub-arrays. It consists in modeling each feed radiation pattern by its active pattern. The numerical implementation is straightforward. The accuracy of the proposed method is demonstrated by considering two numerical examples, namely the analysis of a synthesized elliptical lens and the optimisation of a shaped integrated lens antenna producing two independent radio coverage for short range and long range radars. In both cases, the lenses are illuminated by linear printed arrays.