## 3 The Impact of the Electromagnetic Interference on Drones
### Influence of Electromagnetic Interference of Converter Station on UAV Communication
#### 3.1.1 Impact on UAV Data Link Communication System  
The UAV realizes the information interaction with the control terminal through the data link [18; 19; 20]. The control terminal sends control instructions to the drone through the uplink remote control link, and the drone status parameters and task collection information are fed back to the control terminal through the downlink telemetry link. UAV data links usually use IEEE 802.11 a/n/ac, cellular 3G/4G, or analog systems [21], but these three modes have their own shortcomings. The working frequency band of the IEEE 802.11 protocol is 2.4 GHz, which is within the interference range of the converter equipment, and \begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt} p{142.3 pt}} \hline \hline \multicolumn{2}{c}{**Source of Electromagnetic Interference**} & \multicolumn{2}{c}{**Electromagnetic Coupling Approach**} \\ \hline \multicolumn{2}{c}{UAV power ignition device} & Power port \\ \hline \multirow{3}{*}{In the system} & \multirow{3}{*}{Airborne measurement and control launch equipment} & Digital signal port \\ \cline{3-3}  & & Low frequency analog signal port \\ \cline{3-3}  & & Radio frequency port \\ \cline{3-3}  & & \\ \cline{3-3}  & & \\ \cline{3-3}  & & \\ \cline{3-3}  & & \\ \cline{3-3}  & & \\ \cline{3-3}  & & \\ \cline{3-3}  & & \\ \cline{3-3}  & & \\ \cline{3-3}  & & \\ \cline{3-3}  & & \\ \hline \multirow{3}{*}{Out of the system} & \multirow{3}{*}{Natural electromagnetic phenomenon (high altitude)} & Atmospheric noise \\ \cline{3-3}  & & Cosmic radiation \\ \cline{3-3}  & & Various electromagnetic fields intentionally generated by radio transmitters, and additional electromagnetic fields generated by these transmitters and other technical equipment \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The sources of UAV electromagnetic interference and coupling methods. the broadband interference caused by the converter equipment makes the communication load change the channel and the regional problem cannot be solved. When the interference is too large and the signal-to-noise ratio is lower than a certain threshold, the transmission rate can be automatically reduced from 11 Mb/s to 5.5 Mb/s, or it can be reduced to 2 Mb/s or 1 Mb/s of direct sequence spread spectrum technology. rate. At this time, the information transmission rate cannot even guarantee the flight safety of the drone itself, let alone complete the task. Cellular systems are simple and easy to use and are often provided by mobile operators. They are based on the 802.11 a/b/g standard. They have all the aforementioned shortcomings and are limited by the coverage and signal strength of the cellular network. The anti-interference ability is not strong. Quality is easily affected. The analog signal is easily attenuated during the transmission process, is easily interfered, and has insufficient security. The spectrum efficiency is low (100% duty cycle transmission is required, and cannot work in parallel with other communication technologies). Its advantage lies in almost direct radio frequency signals. Modulation, the delay is very low. The current use of analog signals in UAV communication is not common, so this article will not focus on the description. On the other hand, the UAV communication system, as a special mobile communication system, is inevitably affected by multipath fading and Doppler shift. Due to the wide antenna beam of the communication ground station, the radio signal is divided into two or more copies of the signal and arrives at the receiving antenna through more than multiple paths due to the influence of many factors such as ground features, topography, and the moving speed of the transmitting and receiving ends. In this process, these signal waves interfere, which is called Intersymbol interference (ISI). Because each reflected wave passes through a different path, which affects its phase and amplitude when it reaches the receiving end, when the receiving antenna mixes these signals, there will be distortions in the phase and amplitude, that is, \"fading\" [22].