Yanrong Xue

A new timing method based on common-view

GPS one-way timing is the simplest and most commonly used method for users to acquire precise time. However, it has inferior accuracy in performance as most errors due to satellites and in the path from satellites to users can not be canceled. Common-view time transfer is seen as the improvement of one-way technique and its accuracy is typically in the 1 to 10 ns range. Without exception, common-view time transfer also has limitations. For instance, it is real-time limited and can not be used simultaneously for broad users.

Research on position differential method of dual-satellites TDOA and FDOA in passive location system

Combining with the principle of dual-satellite TDOA and FDOA in passive location system, a position differential method basing on dual-satellite TDOA and FDOA in passive location is put forward, which derives solution position of known and unknown radiation source by using conventional location algorithm method of TDOA and FDOA location, then position correction is achieved by subtracting the exact position and solution position of known radiation source to correct the solution position of unknown radiation source. Simulation results show that, according to similar Geometric Dilution of Precision(GDOP) principle, the known and unknown radiation source at a distance of several hundred kilometers are selected for differential, which can greatly improve location precision. This method develop positioning system of dual-satellite TDOA and FDOA, which has important value for improving its availability and the reliability of positioning result.

Two Methods of Processing System Time Offset in Multi-constellation Integrated System*

Two methods on how to deal with the time offset in multi-constellation navigation systems are discussed in this paper. One approach is disposing time offset in receiver end (DRE) and another disposing in system level (DSL). Comparisons and analysis in different aspects of these two methods are involved. Simulation results indicate that the positioning accuracy of multi-constellation navigation systems is affected more obviously by the method of DSL than DRE. When the error of broadcasted time offset is 5ns, it is more advisable to process time offset use the method of DRE.

System Time Offset Based RAIM in Combined GPS/Beidou Navigation System

Compatibility and interoperability of Global Navigation Satellite System (GNSS) are becoming the main trend of future navigation. However, each navigation system has a time scale. When users positioning with not only one system, the time offset between them must be considered. There are several ways to acquire system time offsets. By adding unknown variables in the combined position equation to solve this variable is the commonly used way. For positioning with multi-constellations, system time offsets are some kind of burden which must be taken into account. This paper takes full use of the obtained offsets and proposes a new fault detection method for Receiver Autonomous Integrity Monitoring (RAIM). Simulations are made to estimate the ability of this new method. This new method takes the high stability of system time offsets of GPS/Beidou system and applies it to assistant fault detection. This method has no additional requirements for navigation system and is fit for applied in receivers. It can be expected this method will be one means of RAIM for Beidou navigation system when integrated with other GNSS in future.

Application of Kalmen Filter for Steering UTC(Lab) to UTC

In order to steer master clock in timekeeping laboratory, it is necessary to identify a suitable algorithm for steering UTC(Lab) to UTC for a period of 45 days. By introducing Kalman Filter into the steering, some considerations which are assumed to effect result are encountered. By compared with the result of quadratic polynomial model, Kalman Filter, based on four years historical data and state parameter initialed by 4 order quadratic polynomial model, is able to predict the plausible results in terms of both stability and accuracy.

Transmission delay measurement for converter

This paper presents two various methods of transmission delay measurement for converter. One is group delay measurement method for multi-lever converter by means of high performance vector network analyzer. The other is envelope method used to determine the absolute delay of a converter using fast sampling scope. A scheme and key technologies of group delay measurement are described. A good measurement example is given and measurement results and their uncertainty are analyzed. It can not represent the real delay when modulation signals pass though the converter, Because the group delay curve measurement is performed by a vector network analyzer which needs the input of sweep frequency stimulation signal. Therefore, the characterization of BPSK modulation signal is analyzed. Transmission delay measurement method of BPSK modulation signal which passes though the converter is researched. Finally, the two measurement results obtained using two methods mentioned above are compared.