# Design and Simulation of Low-Orbit Satellite Broadcast Signal Receiving and Processing Terminal
## 3 Key Technologies  
### Digital Beamforming Technology  
In the business process of traditional low-orbit reconnaissance satellite reception and processing terminals, satellite broadcast signals cannot meet the coverage requirements of high-gain multi-beams [10]. Based on this problem, this design proposes digital beamforming technology, taking low sidelobes and constant gain of array beams into account. 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 [9; 11; 12; 13; 14; 15; 16; 17]. 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. 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. Compared with analog beamforming, the antenna using DBF has better self-correction and low sidelobe performance, which has a far-reaching impact on improving the performance of the receiver [14]. Digital beamforming processes the array received signal in the digital domain and uses the digital beamforming algorithm to calculate the optimal adaptive weighting vector so that the main lobe of the antenna pattern points to the desired direction and the null is aligned with the interference direction, thereby achieving the purpose of spatial domain filtering [14; 15]. Array signal processing in the digital domain can use advanced digital processing technology to make the processing process more flexible and controllable. When the array parameters and target parameters are accurately known, DBF can be used to obtain an approximate optimal output signal-to-interference-to-noise ratio, so that the array antenna can achieve better signal resolution and parameter estimation performance [12; 18]. However, in practical applications, the existence of various errors and non-ideal factors will cause deviations in the steering vector of the desired signal, resulting in a decrease in the gain of the desired signal or even cancellation of the desired signal, which deteriorates the output performance. In addition, high computational complexity is also a problem faced by digital beamforming technology in engineering applications [17]. Therefore, efficient and robust beamforming algorithms have important research significance and practical value. Before signal superposition, digital beamforming needs to adjust the phase between the data of each channel to ensure that the phase error is within a certain range so that the data of each channel can be superimposed to improve the received power and signal-to-noise ratio of the received signal. The digital beamforming software structure is divided into two aspects: beam control and beamforming. Among them, the role of beam control is to align the main beam of the antenna array with the direction of the useful signal, so that the subsequent beam synthesis can maximize the gain of the synthesized useful signal; the role of beam synthesis is to synthesize the useful signal. The control method in this scheme adopts a method based on prior information and spatial domain search. The beam direction is determined by logical control, and then the phase difference between the required superimposed signals is extracted. After compensating for the phase, the beam is superimposed to complete the beamforming [11; 14; 18]. The schematic diagram is shown in Figure 4.  
Among them, the first stage of beam steering first works based on a priori information.