# Design and Simulation of Low-Orbit Satellite Broadcast Signal Receiving and Processing Terminal
## 1 Introduction  
In recent years, with the rapid development of science and technology, satellite communication has gradually become one of the most promising research directions in the current communication industry. Satellite communication is a form of communication that is not restricted by natural conditions such as terrain, landform, and climate, nor is it interfered with by human factors such as national boundaries, politics, and economy, and can achieve information transmission between any two points. Satellite broadcasting signal reception is an important part of the satellite communication process, so research on the reception and processing of satellite broadcasting signals has important theoretical and practical significance [1; 2; 3]. In today's satellite communication field, low-orbit satellites have gradually attracted attention and favor in the world's satellite navigation field with their unique advantages in constellations and signals. The US Iridium system and the GPS jointly developed and launched a new satellite timing and positioning service (STL) based on low-orbit satellites, which has become a backup or supplement to the GPS system; the European Galileo system technical team is also actively promoting the research on the Kepler system, through a low-orbit constellation composed of 4-6 low-orbit satellites, and through inter-satellite links to monitor and measure medium and high-orbit satellites with high precision, so as to greatly improve the orbit determination accuracy of the Galileo constellation. China's low-orbit satellite technology is also developing in full swing. Low-orbit satellite constellationssuch as Hongyan, Integrated Space-Earth Network, and MicroentiSpace have carried out in-orbit tests of experimental satellites [1; 3; 4; 5; 6]. For military uses, the low-orbit satellite broadcast signal receiving terminal is an important space-based intelligence acquisition and combat command receiving component for the realization of the military's multi-service full-dimensional joint operations. In actual military applications, low-orbit reconnaissance satellites will detect enemy targets, process the reconnaissance results on the satellite, and report the results to other satellites or distribute them to the receiving terminals of our detection unit. Finally, the reconnaissance unit will process the results [1; 3; 7; 8]. Low-orbit satellites can provide low-latency, high-speed, and high-reliability mobile communication services. In low-orbit satellite communication scenarios, the movement of the satellite carrier will cause the receiver to have a large Doppler frequency shift and rate of change during the transmission process, requiring high-performance signal capture, tracking, and anti-interference technology to achieve signal synchronization [2; 4; 5; 6]. This article mainly studies how to achieve the reception and processing of low-orbit satellite broadcast signals in the current complex electromagnetic interference environment. Digital beamforming uses digital phase shifting to compensate for the phase difference caused by the path difference caused by the inconsistent RF channel delay and the spatial distance difference for the incident signal in a certain direction, so as to achieve in-phase superposition, thereby achieving the maximum energy reception in that direction and completing the beamforming in that direction to receive the useful desired signal. By changing the beam weight value, the beam is pointed in different directions to achieve beam scanning. Through multi-channel parallel processing, beams in multiple directions are formed at the same time [9]. You can also select a suitable window function to reduce the intensity of the sidelobe level. Beamforming ensures the consistency of the multi-channel phase by correcting the signal phase, and then directly accumulates the multi-channel data to increase the signal power. The antenna using digital beamforming has good self-correction and low sidelobe performance.