Fast low-sidelobe synthesis for large planar array antennas utilizing successive fast Fourier transforms of the array factor

A new and very fast low-sidelobe pattern synthesis method for planar array antennas with periodic element spacing is described. The basic idea of the method is that since the array factor is related to the element excitations through an inverse Fourier transform, the element excitations can be derived from the array factor through a direct Fourier transform. Starting with an initial set of suitable element excitations the array factor is calculated. After matching the array factor to the prescribed pattern, an updated set of excitations is obtained through a direct Fourier transform performed on the matched array factor. From this updated set, only the samples associated with the aperture are retained, where after a new array factor is calculated. The whole process is repeated until the updated array factor does not violate any longer the pattern requirements. The proposed synthesis method provides significant improvements in terms of performance, computational speed, flexibility, and ease of implementation in software to the methods described in reviewed literature. A number of representative examples are presented to demonstrate the various unique capabilities of the method. The results include sum and difference patterns for circular and elliptical aperture shapes featuring uniform ultra low sidelobes.