Hierarchical multiparameter optimization of dual-band wearable antenna

In this paper an optimization method of a dual-band wearable antenna is presented. The antenna geometry is described with 8 geometrical parameters that are automatically adjusted with the use of a evolutionary algorithm to obtain the impedance matching of antenna located in the proximity of a human body. The antenna has been designed to operate in the ISM band which covers the frequency range of 2.4-2.5 GHz and 5.7-5.9 GHz. Within the optimization procedure the direct problem is solved by full wave finite-difference time-domain method to calculate the antenna impedance matching used in the objective function. As the first approach the optimization algorithm was firstly executed in an 8-dimensional parameter space. Subsequently the optimization algorithm was modified so it could start from the reduced set of parameters and then dynamically increase the dimension of the design variable space following the prescribed hierarchy of the parameters. The latter variant of the optimization procedure gave a better solution of the design problem with less computational effort.