Research Of Satellite Time Service Device With GPS System

Time Sevice technology is essential in many aspects in the modern life. There are many kinds of ways about time serve. Among them, satellite time service system has been widely used characterized by all weather, global-mode coverage, high precision, powerful reliability and convenience. Global Positioning System (GPS), the second generation of the Navigation Satellite System, was made in United States in 1993, which were advanced and has been most widedly used.This system real-timely provides the time which is high-synchronic with the universal time to the user. By now, GPS regarded as systemic standard time has been widely used in the fields of the power system, communications, aviation and aerospace.In the present study, we described the synchronous clock method based on the synchronous clock System of GPS and stated that accuracy and stability of the clock pulse of the Synchronous Clock System is the key of the whole synchronous system. By analyzing the availability of the GPS clock and the system error, we proposed that several methods for error standardization in order to increase the frequency measurement accuracy of crystal clock, and explored the jamproof method as well as the solve program of maintaining the normal function of the synchronous clock System after signal becoming invalid.B code is the abbreviate of the time code of IRIG-B. It is an important way for time synchronous transmission and regarded as the first selected standard code of timing equipment because of high performance. By means of B code decoding electric circuit, IRIG-B code transmitted by standard timing equipment is decoded into hour, minute, second, and millisecond information, and imported to the computer for standalization time system of the present machine.The present study described in detail how the system finished from both hardware and software. On the aspect of the hadware, PIC serial micro- controller, which has the powerful jamproof ability, is selected as the main controller and used for central treatment unity. GPS time synchronous system is mainly devided into GPS pre-treatment unit, B code decoding unit, synchronous signal auto-timing circuit, synchronous pulse signal circuit, synchronous pulse signal chosing unit, timing information communication interface, and B code coding circuit. GPS information pre-treatment unit gets out synchronous pulse PPS and timinginformation; B code reads B code information transmitted from other timing synchronous device and gets out synchronous pulse PPS; synchronous signal auto-timing circuit produces synchronous signal by the device itself, which stadars autospecific pulse when the external timing information inputs; synchronous pulse signal chosing unit controls the export way of the synchronous pulse; timing information communication interface and B code coding circuit are responsible for synchronous timing expot. On the aspect of the software, we introduced the ideal of the design of GPS information pre-treatment unit, timing synchronous pulse auto-timing unit and synchronous pulse signal chosing unit.The device was introduced by examples in the present study,including the composition, application, performance index, time sevice ways and the principle, and so on.This system characterized by high accuracy, simple manipulation and active extention, has passed the examination and market launched in batches.There are several limitations in this study. Firstly, accuracy need to be increased. Secondly, overdependence on GPS. Compatibility with other satellite time sevice system needs to be considered, especially with the dipper satellite navigation system in China.