# Wire-Grid and Sparse MoM Antennas: Past Evolution, Present Implementation, and Future Possibilities
## 5 Wire-Grid Sparse Antennas
### Occa Method
#### 5.4.4 Discussion and Future Work  
The OCGA method is under research and further development. This can be explained from the fact that the rectangular grid is universal for any excitations and frequencies, but is far from optimal (for example, by the criterion of reducing the mass and by the criterion of reducing the computational cost of modeling). Taking into account the arbitrariness of the coordinates of the beginning and end of any wire segment, the optimal grid should repeat the directions of the current on the surface and thickening at the places where the changes in the current are sharp. When modeling, this will reduce the order of the matrix of the SLAE that describes the structure (when modeling using MoM). But modeling the surface with a wire grid, according to the flow of currents over the surface, enables manufacturing the object itself not in the form of a real flat surface but in the form of a wire grid. Indeed, there is no need to use, for example, a sheet of solid metal if currents do not flow through it everywhere; it is necessary to leave the metal only where significant currents flow and remove it where insignificant currents flow. Then, for example, it is advisable to switch: from a wire grid to radial conductors; from a grid of strips with the same width to strips with varying widths in accordance with the current density; or from a solid volume to a certain structure with the combined use of the two previous options. Thus, this idea requires more investigation and further development. Till now, this method has been applied to simple wire structures (the entries of the SLAE matrix can be calculated even analytically) using the thin-wire approximation (impulse basis functions and Dirac test functions, according to the classical work by [PERSON]). It is supposed to be used later, even though it requires a correct choice of the segment length at a given wire radius relative to the wavelength. Further study should consider the possibility of reducing the number of antenna elements with a controllable change of their critical characteristics with a given GEET. This is appropriate to reduce the antenna's mass, size, sailing, required memory, and computer time consumption in a multivariate analysis or optimization of the structure on a large number of parameters. Figure 11: Antenna gain at 5.1 GHz obtained using the sparse antenna from the wire-grid structure at 5.9 GHz compared to that obtained using the wire grid (full structure) at 5.1 GHz in E-plane (**a**) and in H-plane (**b**) with GEET = 10%. In addition, it is crucial to investigate another important aspect: the applicability of the proposed approach. Thus, due to the non-use of unnecessary elements, it seems that this is effective for simple requirements (for example, radiation of the antenna at only one frequency). However, in the case of complex requirements (for example, radiation at several frequencies), the efficiency of this method will reduce. Meanwhile, this conclusion is ambiguous: despite the fact that the antenna currents flow differently at different frequencies, a preliminary study of this method showed the ability of the antenna to work in a fairly wide frequency range, such as 6-9 GHz. Moreover, the amplitudes and directions of the antenna currents changed insignificantly. As a result, the received \"sparse\" antenna (at a certain GEET) could easily replace the initial one (full grid). Therefore, it is expedient to investigate this question. Moreover, the possibility and the efficiency of the transition from the orthogonal to the radial wire grid should also be considered, as it will allow the reduction of the redundancy of the orthogonal grid, by reducing by two times the number of segments (by replacing two cathetuses by hypotenuse), and possibly even more, by reducing the number of segments in the polyline (up to the radial line from the source to the structure edge).