# Virtual Validation of In-Flight GNSS Signal Reception during Jamming for Aeronautics Applications
## 3 Installed Performance Analysis  
The approach for assessing the installed performance involved a hybrid method. This hybrid approach, as depicted in Figure 4, utilizes both simulation results and measured data to accurately assess the antenna's performance when installed on the aircraft. First, the antenna design was carried out using commercial software Ansys HFSS (3D High Frequency Simulation Software) 2022 R2. Subsequently, the antenna was manufactured and measured in a semi-anechoic near-field chamber (MVG's Starlab) at the DLR facility. The measured electromagnetic fields in the anechoic chamber were then converted to equivalent currents on an enclosing box. These equivalent currents were used as the antenna source in electromagnetic simulations performed on a digital twin of the D-CODE airplane. A more detailed explanation of the approach is presented in [19].  
Figure 3: Jammer antenna installed on the ground.  
Figure 2: Antenna installed on the aircraft.  
A simplified CAD (Computer Aided Design) model of the mentioned aircraft is available at the DLR facility; it was, therefore, used to simulate the installed performance of the antenna on the aircraft. Figure 5 illustrates both the original D-CODE aircraft and a simulated view of the antenna mounted on the aircraft using the Ansys HFSS. This allows for a visual comparison between the actual aircraft and the simulated antenna installation. Figure 6 shows the radiation pattern of one of the antenna elements of the selected antenna array measured in our Starlab and the radiation pattern obtained after simulating the installed performance of the antenna on aircraft. The reflections emanating from the aircraft contribute to the antenna's installed radiation pattern, resulting in a modification of the overall pattern of the installed antenna.  
Figure 4: Hybrid installed performance scheme.  
Figure 5: DLR’s Dornier DO-228. (**a**) Original. (**b**) Simulated CAD model with installed antenna.  
A similar method has been applied to the jamming antenna, i.e., the GNSS helix antenna from Matterwaves. It was first measured in DLR's Starlab facility as shown in Figure 7. The pattern is then imported into HFSS to obtain the installed pattern of the antenna on the ground (see Figure 8). By considering the ground as a perfect electric conductor (PEC), we obtain insights into the maximum ground reflections, providing us with valuable information about multipath generation from the ground. A square on the ground measuring 100 m in length and breadth is selected with a jammer positioned at its center at a height of 1.6 m.  
In addition to calculating the antenna's installed performance, we also integrate it into the system simulator from Ansys, i.e., STK (Systems Tool Kit) 12, to ensure optimal adherence and comparability to the data obtained from the measurement campaign. Ansys STK is software for digital mission engineering and systems analysis. It provides a physics-based modeling environment for analyzing platforms and payloads in a realistic mission context and provides canonical antenna patterns for the analysis. In our approach, however, the far fields of the simulated installed antenna performance, both for the receiver airborne antenna and jammer antenna, were imported into Ansys STK for a more realistic analysis of the full scenario. This technique provides a more accurate approximation of the actual power levels compared to simpler approaches such as using isotropic elements or built-in antennas in STK, which rely on simplified antenna pattern characteristics, and therefore, do not consider the pattern deformations due to installation in the scenario.  
Figure 6: Radiation pattern of one antenna element. (**a**) Measured pattern in Starlab. (**b**) Installed performance on Aircraft.  
Figure 7: Jammer antenna in Starlab.