# Virtual Validation of In-Flight GNSS Signal Reception during Jamming for Aeronautics Applications
## 4 Full-Scenario Simulation  
### Scenario 1: jamming Power Level Estimation  
In the first scenario, we will analyze the amount of jamming power received at the airborne antenna during flight, as illustrated in Figure 1. In this case, the airborne antenna will receive jamming signals from the lower hemisphere, and hence, the installed performance (considering the shielding from the fuselage as well as the pattern distortions due to the installation) will be essential to obtain accurate information.  
By analyzing the signals received from the jammer acting as the transmitter, it becomes possible to identify specific time intervals during which the jamming effect significantly impacts the reception of signals. These time intervals represent periods when the interference from the jammer has a notable influence on signal quality.  
DLR's in-house developed hardware receiver, i.e., GALANT receiver [20; 21], is used in the measurement campaign, whose simplified block diagram is shown in Figure 9. \(M\) (number of antenna elements) antennas are linked to \(M\) RF frontends, each housing an analog-to-digital converter (ADC), which feeds into the digital signal processing stage. For the sake of comparison between simulation and measurement, the measured power levels at the ADC input will be considered and compared with the jammer-to-noise (J/N) ratio (carrier-to-noise (C/N) ratio of the jammer) obtained from the simulation, as shown in Figure 10. Figure 11 shows the comparison between measured ADC power and simulated J/N in the specific time window where jammer power is highest at reception on the airborne side. As mentioned earlier, our signal reception setup utilizes four L1 elements, resulting in four antenna outputs that are available for comparison in the plots. A very good agreement between simulation and flight data can be observed. Having an estimate of the received interfering power anticipated in a flight scenario is highly beneficial in order to eventually plan countermeasures/adapt the interference suppression algorithms.  
Figure 8: Radiation pattern of jammer antenna. (**a**) Measured pattern in Starlab. (**b**) Installed performance on PEC ground.  
For a more detailed examination of the impact of jamming on individual antenna elements, Figure 12 provides a closer view of each antenna element. In order to obtain reference values, obtainable through easier system simulation, we have performed the same analysis employing not the sophisticated installed performance of the actual antenna, as shown in Figure 4, but a simplified antenna pattern, built-in in Ansys STK. In particular, we have analyzed the case of an isotropic antenna and a GPS \"common patch\" antenna. It is possible to notice in Figure 12 how the simplified simulations are incorrectly estimating the received power: in particular, the simplified patch antenna pattern (apparently a good candidate for the simulation) would totally underestimate the effect of the jammer, as it does not consider the backlobe effects. On the other hand, an isotropic pattern would better approximate the real behavior, but still (due to its strong simplification and the absence of any detailed information about the pattern deformation on the aircraft) provide less accurate results than the ones obtainable with the method we propose, properly considering the installed performance of the antenna.  
Figure 11: Simulation and Measurement results for the flight route (affected duration).  
Figure 10: Simulation and Measurement results for the flight route (full). (Solid lines–Measurement, Dashed lines–Simulation).  
Figure 9: Block diagram of the Galant array receiver.