Fast Antenna Synthesis by an Iterative FFT Procedure

A common requirement in the design of array and reflector antennas is to synthesize an aperture distribution which generates a best possible approximation to a given far field amplitude requirement. Many methods for the solution of this problem are in use, most of them based on optimisation procedures. The present paper describes a technique based on the iterative use of fast Fourier transforms, enabling many iterations to be performed in a short time on modest computers. The method usually converges quickly to a solution, or indicates that one is not possible. An example is given of the method applied to the design of a synthetic aperture radar antenna for an amplitude pattern prescribed in terms of main beam gain ripple and gain slope, with severe restrictions on sidelobe levels in certain directions. The similarity between the proposed method and those in use for phaseless metrology of reflector antennas is indicated.