Genetic optimization of fractal dipole antenna arrays for compact size and improved impedance performance over scan angle

The driving-point impedance of an array element is a function of the self-impedance of the element, the mutual impedances from other array elements, and the array excitation currents. As the beam is steered in a phased array, the driving-point impedances of the array elements will vary with scan angle. This presents a challenging problem in the design of practical phased array systems, especially when considering compact array configurations. This paper introduces a novel approach to the design optimization of compact phased arrays. The new technique introduces fractal dipoles as array elements and uses a genetic algorithm to optimize the shape of each individual fractal element (for self-impedance control) as well as the spacing between these elements (for mutual impedance control) in order to obtain compact array configurations with improved driving-point impedance versus scan angle performance.