RADIATION PATTERN SYNTHESIS FOR MAXIMUM MEAN EFFECTIVE GAIN WITH SPHERICAL WAVE EXPANSIONS AND PARTICLE SWARM TECHNIQUES

A new Mean Effective Gain (MEG) expression using Spherical Wave Expansions (SWE) is presented in order to evaluate the impact of mobile environments on radiating structures. The proposed approach takes into account the pattern polarization and transforms a continuous functional optimization problem into an approximate discrete formulation. It allows to synthesize efficient antenna radiation patterns in terms of the Mean Effective Gain when it is combined with modern heuristic optimization techniques. In addition, antenna performance limits are evaluated by means of certain bounds. These depend on the modal number which is required to describe accurately far fields and depend ultimately on the antenna size. The method estimates the optimum patterns for two different wireless scenarios that are characterized by the statistical probability density functions of incoming waves and particularized in the case of Gaussian statistics. The numerical evaluation has been performed by means of the Particle Swarm Optimization (PSO) technique, which is slightly modified to include a specific constrain and whose parameters have been computed previously by solving a canonical problem. Finally, representative results in outdoor and mixed wireless scenarios are discussed, pointing out some useful consequences in antenna design.