Sun Hongwei

Relations between the Standard Variance and the Allan Variance

Relations between the standard variance and the Allan variance are deduced, and it is concluded that if the “L” in the definition of the Allan variance is an infinite, the Allan variance is equivalent to the standard variance, and that if the standard variance exists and the measurement data are independent of each other, the Allan variance equals the standard variance

Development of Satellite Navigation in China

China completed the first satellite navigation system at 2003. The system named Beidou is an active-mode regional navigation system. The service area of the system covers the east and south Asia. The functions of the system include positioning, short-data communications and time service. During the present time, China is constructing the second-generation satellite navigation system, which named Compass; it will be passive-mode global navigation system including 35 satellites. In addition, China joined Galileo project some years ago.

Impact of Satellite Motion on the Asia-Pacific TWSTFT Links

Impact of satellite motion on the Asia-Pacific TWSTFT links are analyzed and calculated. Based on the satellite motion, three aspects, which are the different distances from two stations to the satellite, time synchronization error in stations, and the Sagnac effect, result in the non-reciprocal path affecting the TWSTFT accuracy

Daily variation in Asia TWSTFT resulting from satellite motion

Based on the satellite motion, two aspects result in diurnal variations in two-way satellite time and frequency transfer (TWSTFT). One is that since the two distances from two stations to the satellite are different, the satellite receives the two signals at different position. Another is that due to the Sagnac effect, diurnal variations in TWSTFT are also produced. It is concluded that the satellite motion can bring the diurnal variations with the amplitude of several tens ps. And the variation primarily results from the satellite longitude and altitude.

A Filter Based on Wavelet Transform

Based on wavelet transform with multi-resolution analysis a filter is designed. The theoretical analysis and simulating results show that the filter not only eliminates the noise effectively, but also reserve the signal structure perfectly.

Performance of time transfer using compass satellite

The impact of satellite position error on satellite common-view time transfer was analyzed. The impact varies depending on the elevation of users and the baseline distance between two users. Some extents of the impact were figured out for several elevations and different baseline. Furthermore, actual results from several common-view time transfer links in mainland of China via compass satellite were given.

Development of deep-space navigation by pulsars in China

In this paper, the fundamental framework of the celestial navigation and the development of pulsar navigation are discussed. Moreover, some results of navigation and timing of the millisecond pulsars in China are also presented.

Determining geo-stationary satellite position using TWSTFT links

Based on several two-way satellite time and frequency transfer (TWSTFT) links and multichannel time transfer modems, a positioning method to geostationary communication satellite is presented, moreover, the accuracy of the positioning is concisely estimated. The characteristics of the method are simple and practical. Especially, the positioning system is completely established on TWSTFT links, so it does not need an extra investment

A filtering means to oscillator noise by using multiresolution analysis

Based on the analysis of the drawbacks of the existent wavelet filtering method, a new filtering noise method and algorithm using multiresolution analysis are set forth. This method not only eliminates the noise effectively, but also protects the signal structure.