## 5 Approached Methodology  
For the purposes of the proposed intelligent unit cell geometry generation tool, a neural network was used: the multilayer perceptron. The design process methodology for a unit cell generation tool metasurface for microwave energy harvesting is shown in Figure 1.  
The overall test work on the geometry generator of the desired unit cell of the metasurface consists of four interdependent stages. The first stage is the design of various configurations of the unit cell of the metasurface in the Comsol Multiphysics environment (Comsol Multiphysics 5.4). On the basis of the unit cell geometry data and the simulation data (step 2) on the resonant frequency found for a given microwave radiation, it is possible to further investigate the capabilities of the multilayer perceptron against the generation of the unit cell geometry. The third stage is the preparation of the data produced in the Comsol Multiphysics 5.4 environment into data readable by the multiarray perceptron. Based on this, the artificial neural network is able to learn the relationship between the geometry and the resonant frequency and generate the desired geometry of the unit cell of the metasurface for the frequency we set (step 4). The project in Comsol Multiphysics 5.4 consists of the design of a unit cell layer with a selected (given) geometry of conducting parts on a dielectric substrate (Figure 2), the generation of a mesh against the created unit cell design (Figure 3), and the study of the electromagnetic field distribution against the given physical properties on the designed structure (Figure 4). The application of periodic boundary conditions on the side walls of the model allows us to perform calculations for a single element only, not the whole array of elements. This noticeably reduces the computation time and effort. Figure 1: The design process methodology for a unit cell generation tool metasurface for microwave energy harvesting. Figure 2: The design of a unit cell layer with a selected (given) geometry of conducting parts on a dielectric substrate in Comsol Multiphysics. For the purpose of testing the intelligent geometry generation tool, 100 different unit cell designs were designed. It was proposed that each unit cell should have the dimension of a quadrant, which can be divided into the dimensions of 36 smaller square blocks (quadrant dimension 6 \(\times\) 6 blocks). For each design of a different unit cell geometry, it was assumed that the entire substrate was created from a dielectric and that the 18 blocks consisted of conductive parts. This means that for a unit cell design, 18 blocks made up the non-conductive part (dielectric), and 18 blocks made up the conductive part. This approach was applied to each of the 100 metasurface unit cell designs. An example of the division of a square into blocks and 2 of the 100 different geometries are shown in the example in Figure 5. By default, the block geometries shown are in the unit cell meta-area plotted on the tile at appropriate distances from the edges. Figure 4: The electric field distribution on the different designed metasurface unit cells in Comsol Multiphysics. Figure 5: (a) The division of a square unit cell into 36 blocks; (b,c) 2 of the 100 geometries used in the design of the unit cell. Figure 3: Mesh of designed metasurface unit cell in Comsol Multiphysics. On the basis of the designs of the unit cells of the metasurface (100 proposed geometries), simulations were carried out showing the absorption behavior of specific cell combinations to the microwave frequency range. The results of the simulations are the reflection coefficient (S\({}_{11}\) parameter) and absorption graphs showing the electromagnetic behavior of the metasurface unit cell, i.e., finding the resonant frequency of the material in question (the most desirable frequency band). Simulations were carried out for microwave frequencies incident on the designed unit cell of the metasurface.