| The subject of this dissertation is the determination of the generator phase for each element in an antenna array so that the peak sidelobe level of the resulting far-field radiation pattern is minimized. In an array of elements it is desirable to use source phase variations, instead of an amplitude taper, to achieve sidelobe reduction and perform beam shaping, since this allows the output capacity of each radiator to be fully utilized.; Phase-only synthesis is discussed for ring arrays, linear arrays, and circular planar arrays. A numerical search technique based on the minimization of an appropriate function of the excitation phases is presented and applied to linear and planar arrays of radiators. Sample patterns are obtained, and the source phase distribution that is required for minimum peak sidelobe patterns is discussed. The effects of mutual coupling, anisotropic radiators, and sidelobe tapers are also discussed.; To circumvent the limitations imposed by limited computer resources, an analytic synthesis technique is presented. The method relies on a statistical model of the excitation phases, and yields reasonable results for very large arrays. Although, for the same size of array, the computer search technique yields better results, the analytic method requires very little computer time, and it is possible to use the technique with essentially any size array of interest.; Finally, the effects of excitation errors and beam steering on the sidelobe levels of arrays are discussed. Data are presented showing the increase in the peak sidelobe level that may be expected as a result of Gaussian amplitude and phase errors, and also the effects of phase quantization that occurs when digital phase shifters are used, and a theoretical basis for understanding the observed effects is developed.; It is concluded that although in most cases there is not cause to recommend phase-only synthesis over amplitude-tapered synthesis from a performance standpoint, phase-only synthesis can be used to simulate most of the pattern characteristics of the optimum amplitude tapers. Thus, if there are additional considerations, not related to array performance, which make phase-only synthesis desirable, it is a viable method for pattern synthesis. (Abstract shortened with permission of author.)... |
