## 3 Results  
The model was applied to the EUT reported in Figure 4a. It is a metallic box having the dimensions 200 mm \(\times\) 90 mm \(\times\) 100 mm, with a rectangular slot (length 75 mm, height 5 mm), centered in the face 200 mm \(\times\) 90 mm. The EUT is fed by a folded dipole connected to the central conductor of an SMA pass-through connector. The EUT was placed into the working volume of a rectangular RC, with the dimensions a = 800 mm, b = 900 mm, and c = 1000 mm. Figure 4: The EUT: (**a**) The real device, used for emission measurements in the reverberation chamber and in the anechoic environment; (**b**) The numerical model, used for full wave simulations. In order to verify the model, the radiation of the EUT was simulated using a full wave numerical tool (Figure 4b) and subsequently measured in an anechoic environment (AE). As regards RC measurements, a vector network analyzer (VNA) was used to measure the scattering matrix between the port used to feed the EUT, and the port was sequentially connected to each monopole placed onto the walls of the RC. Therefore, the VNA measured the amplitude and phase of the parameters of all 2-port scattering matrices because the method, in the proposed formulation, is based on the knowledge of the complex value of the electric field collected at the samples' position. The numerical tool used for simulation is the CST Microwave Studio; in particular, a frequency domain solver was used because we were interested in obtaining results at a single frequency (2 GHz). Measurements in AE were performed by a VNA, used to feed the EUT, connected to port 1 of the instrument. The electric field was measured using a calibrated double ridge horn antenna, connected to port 2 of the VNA. The EUT is located on a turntable, and two planes were considered in these measurements: the E-plane (\(\phi\) = 90\({}^{\circ}\), varying \(\theta\)) and the H-plane (\(\phi\) = 0\({}^{\circ}\), varying \(\theta\)). During these measurements, the antenna was co-polarized with the slot electric field orientation (y). The distance between the EUT and the receiving antenna is 2.3 m, which is smaller than the standard prescription of 3 m due to the environment dimensions and the length constraints of the cables. However, at this distance, the far field condition is fulfilled in the whole analyzed frequency range. Further details of the experimental setup can be found in [18]. The electric field samples were collected using \(N_{S}=120\) monopoles, irregularly distributed onto the chamber walls. The equivalence surface was chosen as a cube having 30 cm on each side and including the EUT. This choice was made to assure that the equivalence surface always includes the EUT, even in the presence of a small positioning error. In [17], it has been demonstrated that the distance between two adjacent equivalent sources should be no more than half a wavelength. In the present case, we chose \(2\Delta_{x}=2\Delta_{y}=2\Delta_{z}=\lambda/4\). Both in the measurements and in the simulations, the considered frequency was 2 GHz. Once the scenario is fixed, a quantitative consideration on the advantage of using equivalent currents parallel to the equivalent surface instead of assuming a volumetric placement of magnetic and electric dipoles can be done. Using a gridding of all the volume included by the equivalent surface, there would be 512 grid points, and by placing three magnetic and three electric currents in each of them, it would need a set of \(N_{eq}=3072\) equivalent sources. Due to the use of the proposed model, there are only 384 subareas; therefore, \(N_{eq}=1536\). The advantage of the proposed method becomes bigger, increasing the dimensions of the EUT, and consequently of the equivalent surface, in terms of wavelength. It must be highlighted that the choice of an iterative procedure to find the values of the equivalent sources allows one to have a non-square \(Z_{ni}\) matrix.