Fengwei Shao’s research while affiliated with Chinese Academy of Sciences and other places

The rapid deployment of satellite constellations has propelled the swift development of the satellite industry. Low-cost solutions spanning the entire industry chain will significantly accelerate the improvement of satellite internet. On the user side, phased array antenna terminals are gradually replacing reflector antennas, yet the ensuing challenges of hardware architecture and costs. Lowering the resolution of phase shifter is one solution, but this may result in a loss of beam pointing accuracy. A novel two-stage phase shifter phased array architecture is proposed, coupling subarray division with mixed-resolution phase shifters to reduce costs while ensuring the beam performance. The architecture boasts low complexity and ease of implementation. Simulation results demonstrate the balanced performance of this architecture in scanning accuracy and beam sidelobes, marking a promising path for industrial applications.

Satellite communication has rapidly advanced, from navigation to broadband Internet and direct mobile connectivity. Driven by low Earth orbit satellites, these networks are merging with terrestrial mobile networks, forming integrated space–air–ground systems. However, the growing scale of satellite constellations has intensified intra‐system interference, particularly among ground cells utilizing co‐frequency beams. A mitigation method based on switching array elements is proposed, optimizing their state by considering beamwidth and maximum sidelobe level. Simulations show that the proposed algorithm effectively reduces beam coverage widening and sidelobes, mitigating the interference between co‐frequency beams.

This study introduces the third-generation BeiDou Navigation Satellite System (BDS-3) system’s creative global operation and service architecture based on regional stations and Ka-band inter-satellite links (ISLs). The architecture’s contributions to BDS-3 include not only combined orbit determination and time synchronization but also autonomous orbit determination and time synchronization, global operations and services. The BDS-3 on-orbit operation results are being presented in the paper to verify the designed capabilities. Compared with BDS-2, the orbit determination accuracy is improving from 0.6 m to 0.15 m, and the time synchronization accuracy is improving from 6.67 ns to 1.16 ns. Under autonomous orbit determination and time synchronization, the 30-day orbit maintenance accuracy reaches 16 m, and the time synchronization accuracy reaches 3.74 ns. The success rate of data transmission reaches 99%, and the delay is better than 12.9 s. In the future, laser ISLs will be used to enhance the system structure and further improve global operation and service capabilities.

As the BeiDou Navigation Satellite System (BDS) is developed form BDS-2regional services to BDS-3 global services, the regional-serving GEO and IGSOsatellites are transformed into global-serving MEO satellites. The observation arcof MEO satellites by regional ground stations is about 1/3. The accuracy of MEOorbit determination and time synchronization would become worse, which wouldmake the global positioning accuracy become unacceptable. It is very hard to pro-vide Radio Navigation Satellite System (RNSS) service and effectively managethe satellite constellation. Different from GPS, GLONASS and Galileo adopt-ing a worldwide ground-stations method, BDS-3 creatively established a globaloperations and services architecture with regional stations and Ka-band Inter-Satellite Links (ISLs). The architecture's contributions to BDS-3 include not onlycombined orbit determination and time synchronization, but autonomous navi-gation, global operations and services. The BDS-3 on-orbit operation results arepresented in the paper to verify the designed capabilities. Compared with BDS-2,the orbit determination accuracy is improved from 0.6m to 0.15m, and the time synchronization accuracy is improved from 6.67ns to 1.16ns. Under autonomousnavigation, the 30-day orbit maintenance accuracy reaches 16m and the timesynchronization accuracy reaches 3.74ns. The success rate of data transmissionreaches 99%, and the delay is better than 12.9s. In the future, laser ISLs will beused to enhance the system structure and further improve global operation andservice capabilities.

By introducing the arrayed waveguide router (AWGR) optical true time-delay (OTTD) architecture in bent-pipe satellite optical inter-link to optically assist the RF phased array in Low-earth orbit satellites will extend the multi-hop bent-pipe satellite beam-hopping protocol proposed in DVB-S2X. It solves the challenge of beam steering with the support of precise, broadband, and wide-range scanning. This architecture utilizes a subarray to combine the advantages of AWGR and a high-precision RF phase shifter to realize the beam pointing without an oblique view. Unlike the traditional digital and analog phased array architecture, the introduction of OTTD can solve the problem of beam squint and also ensure the high-precision scanning of the beam.

As the number of non-geostationary orbit (NGSO) satellites continues to grow, interference with other communication systems, including radio astronomy systems (RASs), is becoming increasingly critical. In this study, an interference simulation framework was developed to analyse the potential impact of NGSO systems on RAS in accordance with the relevant International Telecommunication Union (ITU) regulations and recommendations. In addition to the simulation of interference generated by individual NGSO satellite systems, the framework also supports the analysis of aggregate interference from multiple NGSO satellite systems. By inputting satellite system parameters, including constellation configuration, user distribution and beam scheduling strategy, the framework is able to obtain interference probability distributions for a typical RAS ground station at different latitudes and observation directions. The simulation results provide a reference for the analysis of interference from NGSO satellite systems to RASs, and can also be used to guide the development of strategies to mitigate harmful interference to RASs.

Intersatellite links (ISLs) are an effective way for the global navigation satellite system (GNSS) to reduce its dependence on ground infrastructures, which guarantees constellation orbit determination and satellite communication. When the number of onboard Ka -band antennas is less than that of visible satellites, ISL assignment of GNSS cause a problem. For the problem of ISL scheduling, considering that the result of the allocated link has a feedback effect on the subsequent link assignment as a priori knowledge, an adaptive topology optimization algorithm based on signed variance is proposed. In order to meet the requirements of the communication and ranging performance, the time slots are divided into communication time slots and ranging time slots. Taking the communication time delay from overseas satellites to anchor satellites and position dilution of precision as measurement indexes, the proposed strategy is simulated for 10 080 min. The results show that the ranging performance of this strategy is better than other recently published methods, which verifies the effectiveness of signed variance for adaptive link planning and is also beneficial to the survivability of constellation.

Due to the limitation of the satellite platform, the number of Ka-band Inter-Satellite Links (ISLs) antennas is usually less than that of visible satellites. A topology processing mechanism is proposed based on Finite State Automata (FSA) to link topology optimization with inter-satellite link constraints. Considering the inter-satellite visibility, number of links, and other constraints, a link optimization model is proposed to minimize the maximum Position Dilution of Precision (PDOP) of ranging performance. To solve the problem that the gene mutation mechanism and chromosome crossover mechanism of the traditional genetic algorithm cannot meet the constraints of the optimization model and thus lead to a large number of link conflicts, the Single Point and Traceable Variation (SPTV) mechanism and the chromosome crossover mechanism including Time Slots Crossover (TSX) and Position Self-Crossover (PSX) based on the " hybridization + self-crossover" are proposed. The simulation results show that TSX-PSX mechanism reduces the maximum PDOP by 27. 28% compared with TSX mechanism and avoids the conflict problem, verifying the effectiveness of the improved genetic algorithm for link topology optimization.

Inter-Satellite Links (ISLs) can effectively enhance the Global Navigation Satellite System (GNSS) performance, such as communication and ranging performance. These performances would have been improved by disposing sparsely of ground stations and ISLs. Here, we demonstrate a topology scheduling strategy based on Signed Variance and Blossom algorithm (SV-Blossom) to promote the topology performance of GNSS. We also analyze the effect of this strategy on the robustness of the ranging information quality of the ISLs assignments system. For the domestic and overseas satellite communication Time Delay (TD) and Position Dilution of Precision (PDOP), by analyzing the relation of satellites, a set of the ISLs cost models is established, and the cost matrix is obtained. The final ISLs assignments result is obtained by processing the link cost matrix with the Blossom algorithm in the graph theory. In order to verify the rationality of the SV-Blossom strategy, a typical BDS-3 simulation scene with 10080 min is built to test these performances of ISLs. The final results show that the ranging information quality of the SV-Blossom strategy is greatly improved compared with recently published strategies, and the proposed links assignments mechanism has good robustness.