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The BeiDou regional navigation system has been continuously running for about three years since it starts providing PVT service in December 2012. During this period, it provides more stable positioning and timing service to lots of users in Asia-pacific region. In this paper, the current time transfer performance of BeiDou is tested and analyzed, the performance of its time transfer service which is relative to GPS and other mature satellite navigation system is evaluated. The time transfer technology performance of BDS, such as one-way timing, common view, and precision point positioning time transfer is analyzed and compared with GPS. The experiment of short distance (30km) and long distance (1000km above) time transfer is carried out to evaluate the performance between GPS and BDS. At end of paper, the results of short distance time transfer on GPS and BDS is compared and verified with GPS PPP time transfer. The results of the time transfer performance of the Beidou are in good agreement with GPS time transfer technology, and the relative accuracy is reached sub nanoseconds.

With the developing of the China's Beidou system(BDS), the technology of positioning and time services based on Beidou system which measure the distance between the satellite and ground are more and more widely used and concerned. However, in the positioning and timing solution, the error of satellite clock time difference is one of the main error, which influence the positioning and time services directly. In this paper, the pseudo-range and phase measurements data of Beidou receiver which is operated in the National Time Service Center (NTSC) are used. First the theory of Phase smoothing pseudo is introduced, and the method of combination of dual-frequency eliminated ionosphere pseudo-range and smoothed pseudo-range are used to calculate the result of local and satellite time difference. Some results are obtained by analyzing and calculating, and it shows that the method of phase smoothing pseudo-range can be used in high precision Beidou Satellite clock evaluation.

The two-way satellite time and frequency transfer (TWSTFT) is the most accurate time synchronization method currently. Antenna is an indispensable element and plays an important role in the earth station of TWSTFT, its direction has a definite effect on the signal quality and performance in TWSTFT. In this paper, some preliminary test results are introduced by using the new TWSTFT system of Ku band with a 2.4 meters tracking antenna in National Time Service Center (NTSC). Through the experiment, we have obtained some data according to different antenna direction, by the analysis we can know: the change of azimuth angle is more sensitive than elevation angle during receiving the signal; in theory, the biggest deviation of azimuth angle should be symmetrical in both sides and asymmetric actually, the deviation of elevation angle is also. The deviation is the angle apart from the pointing of antenna at which receiving signal is the best. It can offer a powerful reference for antenna pointing deviation in earth station of TWSTFT and provide theoretical foundation for the antenna direction and high precision time transfer and synchronization.

National Time Service Center, Chinese Academy of Sciences(NTSC) has taken the charge of the national standard time UTC(NTSC). The difference between UTC(NTSC) and UTC has not exceeded ±20ns ever since 2012, which is notable achievements in high precision time-keeping. But short-term(

A new steering strategy is used to monitor and control UTC(NTSC) in this paper. A new atomic time scale TA for real-time monitoring UTC(NTSC) is shown firstly, then the New steering strategy and software proceeding are discussed afterwards. Finally, the results of real steering are discussed, and a successful improvement in steering strategy is showed.

The Common-View time transfer is often adopted in time comparison between two Time Laboratories. With a GPS or Other Global Navigation Satellite System receiver, a few nanoseconds time transfer precision can be gotten. In traditional GPS common-view, single channel C/A code is used for computation. In order to overcome ionospheric delay error, double frequency observed data is used to improve the ionospheric delay computation. In this paper, the common-view time transfer method using Chinese navigation system Satellite GEO and IGSO is tested. The P3 code and carrier phase smoothed P3 code is adopted and tested in the computation. At the end of paper, the precision of this technique is analyzed. The results show that the smoothed P3 Code can reduce the code observation noise and get a better stability.

It is a complex and important job that how to measure and estimate the time & frequency system before designing and evaluating a satellite navigation system. Almost all of the available methods for time & frequency performance measurement are designed for a single equipment or the discrete part. It is considered rarely to measure the performance of time & frequency system as a whole. In this paper, the technical index of time & frequency system to achieve the function of position was been analysed and discussed, and one way is given, from it's performance chain standard range to analyze and evaluate the performance of time & frequency. The method of time & frequency performance chain standard range is used for analyzing the reason and the consistency of time & frequency technical index selection, estimating the rationality of correlative technical index, evaluating the optimal or the worst technical index set. In this paper, the concept is presented and used, a method for measuring and evaluating the time & frequency of satellite navigation systems as a whole is studied.

The paper introduces the microwave time transfer system between timekeeping laboratory in Lintong and time & frequency control laboratory in Pucheng of National Time Service Center. The distance between timekeeping laboratory and time & frequency control laboratory is about 71 km. The microwave time transfer system was reconstructed in 2007, in order to transfer time signal more precisely, the digital channel was added to the system which adopted SATRE Modem to modulate and demodulate 1pps signal. The time comparing data of the digital microwave time transfer system is measured by a counter, the data is sampled once an hour in about one month. Then the wrong data was processed by using some math methods before it is analyzed. By comparing the analyzed result of analog channel with digital channel, the conclusion was put forward at the end of the paper, including the reason that the microwave digital channel is more precise than analog channel and what cause its instability.

As general international standard, inter-range instrumentation group (IRIG) time codes were widely used in modern digital range, monitoring and measurement system, auto-control and commercial fields etc. A new design of IRIG-B code unified time system with high precision using complex programmable logic device (CPLD) technique based on PCI Bus is proposed in this paper. As compared with the original hardware electric circuit, the CPLD technique has lots of advantages such as smaller size, lower costs and the more reliable stability. Modulated and un-modulated IRIG-B time codes are respectively transmitting the information by varying the amplitude of a sine wave carrier and pulse duration modulation of a DC-signal (TTL). The sine carrier wave modulated signal is generated in a digital way by CPLD. The frequency of this signal is derived from the main oscillator of the system, which is disciplined by CNSS (compass navigation satellite system). This leads to a sine carrier wave with high accuracy. Data transfer is synchronized by the 1PPS (pulse per second) derived from the CNSS. Its various outputs like IRIG-B time code, serial time string and 1PPS (Accuracy of pulse outputs: plusmn