Design of Phased Antenna Arrays using Evolutionary Optimization Techniques

Mobile and wireless communication systems have now arrived at the point where substancial advances in antenna technology have become a critical issue. The majority of these systems consist of an antenna array combined with an appropriate signal processing (Soni et al., 2002; Godara, 2002), i.e., the antenna elements are allowed to work in concert by means of array element phasing, which is accomplished with hardware or is performed digitally. In these systems, the antenna array performance over a certain steering range is of primary concern. In this case, the antenna array design problem consists of finding weights that make the radiation pattern satisfy the desired characteristics (a maximum directivity, a minimum side lobe level, etc), so the direction of the main beam can be steered at will. Generally, the design problem is formulated as an optimization problem. The design of antenna arrays has a nonlinear and non-convex dependence of elements parameters [Kurup et al. 2003], because of that, the interest has been focused on stochastic search techniques, such as simulated annealing (Murino et al., 1996), and mainly, genetic algorithms (GA’s) (Ares-Pena et al., 1999; Haupt, 1994; Haupt, 1995; Panduro et al., 2005; Rahmat-Samii et al, 1999; Weile et al., 1997; Yan et al., 1997), widely used in electromagnetic problems, including the synthesis of phased antenna arrays (Mailloux, 2005; Hansen, 1998). The antenna arrays optimization for improving performance represents an open line of research in the antenna design field. In the application of evolutionary optimization techniques for designing antenna arrays, it has been considered the design of different phased array structures, such as the linear arrays (Bray et al., 2002; Panduro, 2006) and the circular arrays (Panduro et al., 2006), among others. The design of planar arrays is dealt with in (Bae et al., 2005). In many design cases, it has been considered the optimization in the design of scannable arrays with non-uniform separation (Bray et al., 2002; Bae et al., 2004; Junker et al., 1998; Tian et al., 2005; Lommi et al., 2002). In this chapter it is considered the case of designing scannable arrays with the optimization of the amplitude and phase excitations for maximum side lobe level reduction in a wide scanning range. The purpose of this chapter is to investigate the behavior of the radiation pattern for the design of different phased array structures (linear and circular arrays) considering the O pe n A cc es s D at ab as e w w w .ite ch on lin e. co m