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 toNtimes element gain, whereNis 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 forN ≥ 14, and data are presented forNas high as 50. Specifically, sidelobe levels of 15.54, 16.54, 17.86, and 18.56 dB are obtained forN = 18, 31, 37, and 44, respectively. Although the improvement is modest for lowN, it appears that the available improvement increases directly withN.