Optimization of Multiple-Short PIFA for Broadband Communication Kisangiri Michael * , Andrzej A. Kucharski * * Wrocław University of Technology, Wrocław, Poland Abstract— As wireless systems gain wider acceptance and enjoy increased application, performance and cost constraints on the wireless system antennas become more difficult to meet. In this context, antennas that are small in size, inexpensive to manufacture, conformal or are low-profile and that exhibit broadband or dual-band operation are of particular interest. In this paper we apply an optimization technique for multi-short PIFA antennas based on combining a genetic algorithm (GA) and Method of Moments (MoM) technique. The GA optimizes the position of shorting patches in antenna model together with the shape of the radiator itself, in order to obtain a specific frequency response. Recalculation of the MoM interaction matrix for each individual in the GA is avoided by application of DMM (Direct Matrix Manipulation) I. INTRODUCTION The current development in wireless telecommuni- cation industry in which mobile devices are smaller in size and multifunctional, requires mobile phone antenna which is small, simple and at the same time fulfill electrical specification of a specified system. The existing designs, especially those exhibiting wideband or multiband operation, have been developed through careful application of engineering judgment and expertise to extend the canonical designs and/or through serendipitous discovery [1]. Either way, the development of new designs is often a slow, haphazard process that often yields designs that are difficult to manufacture and, therefore, unsuitable for commercial wireless antenna applications. What is needed is a new approach that allows the designer to specify design goals and then generate a candidate “optimal” structure in a methodical and evolutionary manner. An approach that holds much promise in this regard is the coupling of full-wave electromagnetic modeling codes with optimization methods. The Planar Inverted-F Antenna (PIFA) has found widespread internal utilization within wireless terminals due to its small size for both single and multi band applications. The PIFA has many known mechanical advantages, e.g. ease of fabrication, low manufacturing cost, ground plane compatibility and conformity with complex geometries. PIFA antenna with three shorting patches will be examined in this paper. II. GA/MOM METHODOLOGY Genetic algorithms are a probabilistic search approach, which are founded on the ideas of evolutionary processes. The GA procedure is based on the Darwinian principle of survival of the fittest. GA optimizer process, as shown in Fig. 1, begins by producing randomly distributed initial population. After the initial population is formed and fitness values assigned to each member of the population, a reproductive loop, consisting of a selection, cross over, and mutation operators, is performed until enough new individuals are generated to fill the new generation. When a new generation has been completely filled, it replaces the old generation and, if the termination criterion has not been met, a new round of selection, crossover, and mutation begins [4]. The goal of the investigation is to develop a means for generating an optimal or near optimal antenna structure in a methodical manner. The approach that is adopted in the GA/MoM is to begin with a mother structure and then derive substructures from it through an interactive GA search with MoM as the basic research Method. The method of moments (MoM) solution used in this research relies on RWG (Rao–Wilton–Glisson) edge elements. First the surface of a metal antenna under study is discretized into right triangles as shown in Fig. 2 Each pair of triangles, having a common edge, constitutes the corresponding RWG edge element. Thus the division of the antenna structure into RWG edge elements approximately corresponds to the division of the antenna current into small “elementary” electric dipoles. Impedance matrix Z describes the interaction between different elements. The size of the impedance matrix Z is equal to the number of the edge elements [2]. Every edge has its corresponding row and column in the mother Z-matrix of the PIFA antenna model. Fig. 1. Genetic algorithm flowchart [1]