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 N times element gain, where N 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 N > 14, and data are presented for N as high as 50. Specifically, sidelobe levels of 15.54, 16.54, 17.86, and 18.56 dB are obtained for N = 18, 31, 37, and 44, respectively. Although the improvement is modest for low N, it appears that the available improvement increases directly with N. Copyright © 1969 by The Institute of Electrical and Electronics Engineers, Inc.