GEOMETRY PARAMETERS OF FREQUENCY SELECTIVE SCREENS OPTIMIZATION
The procedure of frequency selective screens synthesis is the aim of the paper. The initial condition is the requirement to the shape of scattering matrix elements frequency dependences. As the synthesized parameters there are used geometric dimensions that define shape of the screen periodic array. It is noted that the success, quality and speed of solving the synthesis problem (calculation of optimized set of screen parameters) is substantially determined by specifying the initial approximation. To determine the correct choice of the initial approximation there were made a considerable number of preliminary computational experiments allowed to offer the most convenient configuration of the screen Floquet cell and identify "most sensitive" geometric parameters of the screen, which values selection is implemented in the optimization process. It is shown that while frequency characteristics optimization it's more appropriate to use so called interpolation synthesis technique with applying one of the known optimization procedure. Several examples demonstrated that for practical applications is sufficient to put the values of the frequency characteristics in limited number of controlled points. Questions of constructing the objective function of the problem optimization and methods of setting system restrictions on the desired solution. It's recommended to fix a number of parameters, for example, the values of dielectric constant and thickness of the layers, and to determine characteristic geometric dimensions, which define the configuration of the screen element in the periodic array. Synthesis problems results for several types of frequency selective screens, each of them represents itself as three-layer system of periodic lattices square patch with rectangular shape and (or ) cruciform recesses. There are shown the initial values of the parameters to be optimized and the corresponding frequency response. Minimizing procedure of the objective function is made by one of genetic algorithm methods. The results of optimization problem solution are presented as a set of parameters and display the synthesized frequency characteristics. There was made an experimental verification of laboratory model of frequency selective screen, built on the results of the theoretical problem solution. A comparison of results of calculations and experiments are discussed.