Reduced sidelobes for Butler-matrix-fed linear arrays

It is shown that simple transposition of the elements of a linear array fed by a Butler matrix can be used to improve the sidelobe level without significant degradation of the other characteristics of the array. The beams remain collimated with gain equal to times element gain, where is the number of elements in the array. The beam crossover level is lowered slightly but not so much as would be the case for a conventionally tapered aperture distribution. Improved sidelobes are obtained for , and data are presented for as high as 50. Specifically, sidelobe levels of 15.54, 16.54, 17.86, and 18.56 dB are obtained for , and 44, respectively. Although the improvement is modest for low , it appears that the available improvement increases directly with .