We present the design and experimental results of an X-band unequally spaced reflectarray of microstrip patch elements. For a given number of elements, it is shown that reduced sidelobe levels can be attained for unequally spaced reflectarrays compared to that of equally spaced reflectarrays with no significant change in directivity and array size. The synthesis tool used for deriving the element positions is a variant of the genetic algorithm, namely the differential evolution algorithm.
Dr. Dhanesh G. Kurup, Himdi, M., and Rydberg, A., “Design of an unequally spaced reflect-array”, IEEE Antennas and Wireless Propagation Letters , vol. 2, pp. 33-35, 2003.