# Wire-Grid and Sparse MoM Antennas: Past Evolution, Present Implementation, and Future Possibilities
## 5 Wire-Grid Sparse Antennas
### Overview
In this case, the required computational cost significantly decreases, and the obtained results are in good agreement with the experimental ones [279]. In [280] it is shown that when exciting a parallel wire grid located near a flat interface between two homogeneous media with an electromagnetic wave, polarized so that the magnetic field vector is perpendicular to the gird, it can be represented by a shunt element in an equivalent transmission line circuit. In the work [281], the researchers investigated the application of the iterative method to solve a SLAE obtained by representing a spherical antenna by a grid of wires. They also established the optimal parameters of the method, which give close results to those obtained theoretically. The work [282] presents an effective computational method for obtaining RCS of an electrically small aircraft, the fuselage of which is described by a grid of wires. It is shown that with the correct choice of the wire segments' radii, the simulation and experimental results are close for the polarization of the incident wave parallel to the fuselage axis. In the case when the polarization is perpendicular, the agreement of results is worse. In [283], a method for estimating the scattering of a rectangular wire grid, based on the use of CG and fast Fourier transform methods, is proposed. In addition, the principle of equivalent radius is used to determine the reflection coefficient. In [284], an example of the scattering problem for an infinite circular cylinder is used to analyze the influence of the wire diameter of the wires on the modeling accuracy. It is shown that the best accuracy is achieved when the wire satisfies the empirical rule of \"equal surface area\". At the same time, it is revealed that wires that are too thick are just as harmful as wires that are too thin. In addition, it is shown that the observance of boundary conditions between the wires is not a reliable check on the validity of the simulation results. Regarding antenna tasks, the authors in [285] present the results of the development of a wire-grid-antenna modeling system, and in [286] the NEC system, which is used to estimate characteristics such as average power gain and electric near and far fields of a monopole antenna mounted on a cubic base over a perfectly conducting ground plane. It is shown that the simulation results are in good agreement with the experimental data and the results of another independent electromagnetic modeling code. In [287], a new methodology is proposed to calculate scattering characteristics of three-dimensional conducting bodies of an arbitrary shape, and the features of the modeling system that implements it are described. In the work [288], the peculiarities of the development of a graphical user interface of a GEMACS antenna modeling system are presented. In the work [289], the authors considered a number of problems arising that simulate complex three-dimensional configurations, such as the antenna-airplane system, where the fuselage of the aircraft is approximated by a grid of wires. It is shown that, despite some limitations, the results can be obtained with acceptable accuracy. In [290] an algorithm for local mesh partitioning is considered that takes into account the discontinuous nature of the interface between large and small cells for a smooth transition of strongly varying field components. In the paper [291] the convergence of the wire-grid model is evaluated when the number of grid cells changes. This allowed the researchers to obtain correlations between the minimum grid size and the required modeling error. Ultimately, the researchers determined the sensitivity of the original antenna design to small changes in its shape. After creating RWG functions [292] that are used to describe surfaces by a set of triangles, the application of wire grids has become less popular.