Quasi 5 foci Rotman-Turner Discrete Lens Antennas with Minimised Optical Aberrations

Discrete Lens Antennas guarantee several advantages including a true time delay behavior, simplified beamforming networks, large field of view, high number of radiated beams. Despite to several papers proposed on the design and applications of two-dimensional constrained lens antennas, and in particular on the Rotman-Turner lens, a rigorous study focused on the minimization of optical aberrations does not seem to be available. The main results of a general procedure for the design of two-dimensional bootlace lens antennas with a flat front profile are proposed in this paper. It will be shown that the best performance is achievable when, in addition to the three nominal focal points, two additional symmetric quasi foci are present. It will be shown also that a completely different two-dimensional discrete lens, characterized again by a flat profile and 4 focal points, presents minimized aberrations when the presence of one additional quasi focus on the lens axis is guaranteed. Interestingly, both the 3- and 4-foci lenses, when optimized, converge to the same configuration which exhibits aberrations following a Chebyshev-like behavior and guarantees quasi 5 foci.