High-Precision Time-Frequency Broadcasting System under GNSS Rejection Situation

The high-precision time-frequency is a crucial strategic resource for any country, serving as the bedrock for national defense construction and economic operations. Global Navigation Satellite Systems (GNSS) provides timing service through satellite, which has the characteristics of all-weather, high-precision and wide coverage. It has become an indispensable means of timing service. However, GNSS signal can be disrupted under certain conditions, leading to service interruptions and preventing users from obtaining accurate time information. This paper introduces a time-frequency broadcasting system utilizing the BeiDou Navigation Satellite System (BDS) signal system in scenarios when GNSS is unavailable. By acquiring and calculating the BDS ephemeris data, the system calculates the BDS coordinate information according to the local time in real-time, simulates the satellite trajectory, adjusts the time of broadcasting according to the local position input, and generates the corrected satellite navigation message information. The time-frequency broadcasting system can provide real-time timing service for BDS navigation terminals within the coverage area. The timing accuracy of the system is better than 6.3 nanoseconds, the project implementation is feasible, and the application range is wide. In the case of no GNSS, the system can also provide emergency timing service for BDS navigation terminals within the coverage area.