Research On CINRAD Clock Synchronization Hased On NTP Protocol

Chinese Next Generation Radar (CINRAD) is one of the advanced weather radars in the world today. It plays a huge role in weather forecasting and early warning systems of disaster prevention and mitigation. In practice, the timing accuracy of radar data is directly related to the disaster weather prediction and identification. Therefore, business rules have been released to specify the timing precision of the radar systems. At present, manual dialing clock synchronization is commonly used. In addition, the accuracy of high-voltage/low-voltage working time of the radar is also an important issue which relies on manual recording at present. Aiming at filling the inadequacy of existent techniques, we have developed an automatic clock synchronization system for CINRAD based on NTP protocol.The system hardware platform uses ARM9-based industrial terminal as a NTP server and accesses to CINRAD network via the standard Ethernet port. The clock synchronization functions by running NTP server software. The12-channel timing GPS receiver is employed as standard time source. The high-voltage/low-voltage working time collecting device is designed based on AT89C52microcontroller, where ADS7804is employed to perform sampling. It communicates with NTP server via the RS232-TCP/IP converter.The NTP server software and client-side timing software are developed based on Microsoft.NET2005and NET Compact Framework2.0Functions of the NTP server software include NMEA packet analysis, standard time source selection, NTP synchronization request response, low and high voltage working time management and so on. To monitor the status of the radar system conveniently, touch-screen-based interactive interface has been designed to display real-time information. The NTP client software adopts UDP connection mode. A master-and-slave type automatic clock synchronization between NTP server and client is realized by using Winsock library.To deal with the problem of GPS error, a linear statistical processing mechanism has been proposed. Specifically, linear prediction and sliding window method are employed to mitigate the influence of the error of GPS standard time source.The clock synchronization system of CINRAD has been tested in a number of radar stations. The test results reveal that the system design is successful, and can be used to improve the accuracy of clock synchronization effectively.