1. Satellite communication application scenarios
Satellite communication has the advantages of no line-of-sight limitations, dedicated channels, and good confidentiality. Satellite communication can realize data communication between any two terminals within the satellite coverage area.
(1) Non-line-of-sight communications
Due to the influence of the curvature of the earth, if the two terminals cannot be kept "visible", the traditional data communication will be blocked by the earth's surface, resulting in poor communication quality, or even communication interruption, at this time satellite communication is a good means. The common situation is that in the case of ground-to-ground communication and air-to-ground communication (the aircraft flight altitude is relatively low), the "visibility" between the two terminals cannot be maintained, and satellite communication should be used at this time.
In special occasions such as mountainous areas and forests, the surrounding environment is complex, the occlusion is more serious, the conventional communication mode communication distance is limited, and long-distance transmission cannot be realized, so the use of satellite communication can effectively break through this obstacle.
(2) Long-distance communication
In the case of air-to-ground communication, the communication distance is 150km~200km, and satellite communication should be considered if you want to continue to increase the communication distance.
(3) Real-time
Satellite communication is real-time communication, the communication delay is about hundreds of ms, can transmit real-time video, audio and data to the monitoring station, which is convenient for the monitoring station to analyze and process the data in real time, and provides a basis for remote control and decision-making. If the way of satellite communication is not adopted, in the case that the traditional communication means cannot be realized, the record data can only be archived, and then processed afterwards, which will greatly reduce the efficiency of the test and work.
2. Unmanned aerial vehicle (UAV) satellite communication system
The UAV satellite communication system consists of an airborne satellite communication terminal (airborne station), a ground satellite communication station (ground station), a vehicle-mounted satellite communication station (vehicle-mounted station) and a network management system, as shown in the figure below.
The airborne satellite communication terminal comprises an airborne dynamic communication antenna, an airborne satellite communication terminal, an airborne power amplifier and other supporting equipment. The communication terminal is integrated with a satellite communication modem, an audio and video data codec, a task controller and a data processor.
The vehicle-mounted satellite communication station includes a vehicle-mounted satellite static antenna, a vehicle-mounted satellite communication terminal, a vehicle-mounted power amplifier, a ground network management terminal and other supporting equipment. The vehicle-mounted satellite communication station can be built separately by using an independent cabin, or it can be installed and modified on the basis of the already built vehicle-mounted command station.
According to the actual operation needs of users, a set of ground fixed accusation stations can also be built. The composition of the ground control station is basically the same as that of the vehicle-mounted communication station, and the ground fixed control station communicates with the dispatch room of the user headquarters through a wired network.
3. Classification of UAV satellite communication systems
UAV satellite communication systems are divided into the following two categories according to application scenarios:
(1) Rotorcraft helicopters
Rotary-wing helicopters often lead to ground communication interruptions due to the influence of helicopter flight altitude and complex terrain conditions, which brings certain safety risks, so it is very necessary to use satellite communication systems. The installation of satellite communication system in rotary-wing helicopters focuses on solving the problem of communication reliability under rotor conditions.
(2) Fixed-wing UAVs
Due to the large coverage of long-endurance fixed-wing UAVs, reliable communication cannot be guaranteed in the case of over-the-horizon. The satellite-based airborne satellite communication system can realize reliable and high-speed communication of long-endurance UAVs throughout the range.
4. The main features of the UAV airborne satellite communication system
1) Fully independent intellectual property rights
Airborne dynamic communication antenna, airborne communication terminal and ground communication terminal are all independent property rights, safe and reliable, master all technical details, can be adapted to the application, the antenna full carbon fiber surface mold, to ensure the consistency of production.
2) Low operating threshold
It is about 2dB lower than that of domestic competitors. Under the same conditions, the lower the demodulation threshold, the more link margin, and the higher the reliability, that is, the system availability is stronger, the transmission data rate is higher, and the channel capacity is larger in remote areas with poor satellite coverage.
3) Burst communication in the case of rotors
It has the ability of automatic rotor detection and data rotor gap transmission, and is in the best position among similar products in China. The time occupied by the burst transmission of data is short, and the probability of being blocked by the rotor of the helicopter is low. By rationally designing the frame structure and retransmission mechanism, the transmission efficiency can be improved under the premise of ensuring the reliability of communication.
4) High spectrum utilization:
The filter roll-off coefficient is 0.15, and other domestic products are 0.4 or 0.5, which reduces the occupied satellite bandwidth and reduces the cost of renting satellite resources for customers.
5) Low power spectral density
A low threshold means low transmit power and low power spectral density, which can be further reduced by spreading spectrum to prevent interference from neighbor satellites and increase system availability.
6) One station multi-machine function
It has the function of multi-aircraft cluster management at one station, and realizes that a set of ground stations can manage multiple aircraft at the same time.