Gain limitations of large antennas

Arrays of many elements and continuous aperture antennas are very often designed using Taylor\´s "approximate" space factor which is optimum in resolution, i.e., it offers minimum beamwidth for a given sidelobe ratio. This space factor has a number of equal level sidelobes followed by tapered lobes, the latter being necessary to make the aperture function physically realizable. For conventional antennas, these designs offer gain which, while not that of a uniform aperture, is quite satisfactory. Very long (or large) antennas with their narrow beamwidths, however, may exhibit a severe gain degradation due to large energy contained in the sidelobes. Thus the sidelobe behavior must be carefully controlled to realize the full gain available. Data are presented for the gain variation of various Taylor equal sidelobe designs, and of the modified sin one-parameter family as a function of aperture length.