## 2 Overview of the SOTM System  
### Principle of Satellite Tracking for SOTM Antennas  
Currently, the majority of SOTM systems utilize conventional parabolic antennas. However, these antennas have several drawbacks, including large physical dimensions, low wind resistance, mechanical inertia during scanning, and slow tracking speed. As a result, they suffer from compromised communication reliability and security.  
Compared to the parabolic antenna, the array antenna is a new high-tech satellite antenna. The array antenna is generally not indivisible but consists of multiple antenna elements, each of which can form a similar and non-directional antenna pattern. Althoughthe gain of each individual antenna element in the array antenna is low, the collective effect of numerous well-designed and properly arranged elements results in a relatively high gain for the array antenna. Therefore, the array antenna meets the requirements of satellite communication systems. The phase between the signals of each antenna element in the array antenna can be adjusted, enabling the beam direction of the overall array antenna to be adjusted without the need for a mechanical system. The array antenna has the advantages of low delay in directional adjustment, high system capacity, strong anti-interference ability, and being lightweight.  
Figure 1 illustrates the communication link structure of the SOTM system. The satellite ground station remains in a stationary state relative to the Earth's surface. It establishes wired communication links with the Internet Service Provider (ISP), command center, etc. Simultaneously, it establishes wireless communication links with communication satellites.  
The SOTM antenna is installed on a moving carrier, its location remains relatively stationary with respect to the moving carrier, and the communication link is established through wireless means. Network devices, such as modems and routers, primarily handle tasks such as data forwarding. They typically establish communication links with the SOTM system through cables. Additionally, they establish links with user terminal devices such as closed-circuit television (CCTV), personal computers (PC), smartphones (SP), etc., through cables or wireless communication; this enables the establishment of a complete communication link between the user's terminal devices and entities such as the ISP and command center.  
The carrier's movement requires the SOTM antenna to continuously align with the communication satellite, ensuring a stable communication link. Figure 2 depicts the structure of the SOTM system's servo control system. Because the carrier may be in a moving state, the location and attitude of the carrier may change.  
The SOTM system attitude calculation processor calculates the real-time attitude of the carrier through the fusion of the gyroscope, accelerometer, GNSS, and electronic compass. The SOTM main controller calculates the direction of the antenna beam based on the longitude, latitude, and altitude of the communication satellite, as well as the location and attitude of the carrier. The main controller adjusts the array antenna beam's azimuth and elevation in real-time to track the communication satellite.  
Figure 1: Overview of the communication link of the SOTM.