A.O. Manichev, A.S. Kondratiev

Formation of pattern nulls is an efficient method for reducing the influence of artificial and natural interferences. Here, phase-only synthesis methods are most attractive, because allow simple implementation without an additional hardware. At present, there are a large number of phase-only synthesis methods. However, in selection of the most appropriate method, the designer often has an insufficient amount of information: the authors test the proposed methods on antenna arrays having different configurations and by solutions of different problems (for example, the problem of formation of flat-top patterns with prescribed nulls rather than only the null synthesis problem). Data on the operation speed of the proposed methods are also difficult to compare, because these data (if present) are obtained under different operating conditions. In the first part of this paper, most popular phase-only synthesis methods are classified and their principles of operation are briefly described. In the second part, model data for solution of several important synthesis problems (formation of one null in the maximum of the first sidelobe and in a set of spatial directions, simultaneous formation of two local nulls situated symmetrically or in randomly generated directions, and formation of a group of five closely spaced nulls placed near the maximum of the first sidelobe and for a set of different spatial directions) are presented. Analysis of these data shows that, at present, the univariate phase-only synthesis method is optimal for most practical problems, because it ensures fast and reliable formation of deep nulls for arrays with quantized phase shifters. The performance data of the univariate synthesis methods can be improved if the use of this method is preceded by several iterations of the linearization method proposed by Hans Steyskal. In order to obtain deeper nulls, bi-coordinate synthesis methods can be used. However, extension of the space of variables to two substantially decreases the operation speed. Therefore, at present, combinations involving such methods are basically of theoretical rather than practical interest.