# Analysis of Electromagnetic Interference Effects of 5G Signals on Radio Altimeters
## 3 Simulation of 5G Signal Injection
### Interference Effect Simulation and Results Analysis  
In the simulation, the power of the echo signal injected at the RA RF front-end is set at \(-60\) dBm, with a center frequency of 4000 MHz and a bandwidth of 10 MHz. The power is gradually increased from \(-70\) dBm to 15 dBm in increments of 5 dBm. By observing the gain of the echo signal at the LNA, as well as the power and gain of the final output IF signal, we can analyze the impact of 5G signals on the gain compression effect of IF signals. Figure 5 illustrates that as the injected 5G signal power increases, the echo signal stabilizes at approximately 18.79 dBm during the initial phase of the LNA gain, while the IF signal power stabilizes at 15.13 dBm. In comparison to the input echo signal power, the IF signal gain remains stable at 56.79 dBm during this phase. As the 5G signal power rises to around \(-20\) dBm, the LNA gain begins to decline, leading to a significant decrease in both the power and gain of the IF signal, which exhibits a downward trend in tandem with the increasing 5G signal power. The simulation results indicate that at low 5G signal power levels, the RA RF front-end effectively mitigates interference, thereby maintaining the stability of the IF signal. However, once the 5G signal power surpasses a certain threshold, the LNA enters a saturation state, resulting in a marked reduction in amplification capability and a detrimental impact on the signal gain. At this juncture, the 5G signal power considerably exceeds the echo signal power, compromising the signal processing and amplification functions of the RF front-end. This indicates that the strong interference of the 5G signal significantly weakens the effectiveness of the echo signal and affects the overall performance of the RA RF front-end. In Equation (15), the main parameters affecting the IF signal gain include the power and frequency of the 5G signal. The above parameters are changed to simulate and analyze the interference injection of 5G signals into the RA RF front-end, and the results are shown in Figures 6 and 7. Figure 4: Frequency-domain waveform of the 5G NR TM1.1. The IF power spectrum of the RA under the interference of 5G signals with different powers is shown in Figure 6. When there is no 5G signal interference, the power of the IF signal is 15.25 dBm, and the frequency is 400 kHz. When the interference signal power is \(-33\) dBm, the power spectrum of the IF signal is essentially the same as that without interference, indicating that the 5G signal power does not cause the RF front-end to become overloaded at this time. However, when the interfering signal power increases to \(-23\) dBm, the IF signal power decreases significantly. As the 5G signal power increases, the gain compression effect of the IF signal becomes more pronounced. When the interfering signal power is further increased to \(-13\) dBm, the IF signal power decreases further to 5.47 dBm, and the gain compression effect becomes particularly significant, indicating that the 5G interfering signal has caused more severe interference to the echo signal, leading to a  
Figure 5: Power variation with 5G signal power. Figure 6: IF output under different 5G signal power injections. significant decrease in system performance. It can be seen that with the increase in the 5G interference signal power, the gain compression effect of the RF front-end becomes more pronounced. Figure 7 illustrates the output IF power spectrum of the RA receiver when affected by the 5G signal at different center frequencies. At the same 5G signal power of \(-20\) dBm, it is evident that the closer the center frequency of the 5G interference signal is to the working band of the echo signal, the more obvious the IF signal gain compression effect becomes.