Creating and optimizing microstrip antennas using the genetic algorithm and the finite difference time domain method

The current trend for wireless devices is to make them integrated and smaller. While mobile devices are getting smaller, physical laws that dictate the size of antennas are constant.; Current conventional multiband antennas have limited bandwidth and efficiency. Dual band antennas are difficult to design, and designing tri-band antennas with wide bandwidth, high efficiency and small size is extremely difficult using conventional design methods. Current antennas designed with the genetic algorithm often take excessive computational time and are generally limited to simulation methods that do not allow heterogeneous materials nearby.; This research has three goals to overcome these problems. The first is to improve the usability of the GA-FDTD (genetic algorithm-finite difference time domain) antenna design method. The graphical interface GAVU has been developed that integrates an effective, flexible cost function with the GA for designing broadband and multiband antennas simulated using the FDTD method.; The second goal is to reduce optimization time. This can be accomplished by reducing individual FDTD simulation time, and by finding optimal GA parameters. Methods are developed to reduce FDTD simulation times. These relatively course simulations run very fast and produce results that are good enough to quickly develop broadband antennas. The best GA parameters are determined through a parametric study to find the best population size and mutation rate for designing amorphous ellipse antennas.; The third goal is to select from the research literature the best GA antenna type to produce broadband results. Also, a novel GA antenna type is studied that uses ellipses to generate amorphous designs. These amorphous ellipse antennas produce results that are much better than those reported in the literature. Results from comparing amorphous, waffle, and arbitrary strip monopole antennas show that each GA antenna type has its own strengths and limitations.; The application of these improvements was demonstrated by designing small multiband and broadband antennas that have much greater bandwidths than are currently available and that can be designed at the desired frequency bands in a relatively short period of time using fast FDTD simulation methods and optimized GA parameters.