| The continuous development of atomic clock technology has led to higher and higher requirements for high-precision time synchronization,and high-precision time synchronization plays an important role,especially in the important fields of deep space exploration,aerospace,positioning and navigation.For the traditional two-way satellite time transfer(TWSTT)and the common-view global positioning system(GPS)time transfer,the accuracy of their time synchronization transmission cannot meet the current demand for the accuracy of long-distance time synchronization due to environmental and other uncertainties.With the advantages of wide coverage,good electromagnetic resistance and low loss,optical fiber is widely used in long-distance optical fiber time transmission system.In the time synchronization system,1 Pulse Per Second(1PPS)signal is usually used as the synchronization signal,and the time interval counter takes the rising edge of 1PPS signal as the judgment basis.Therefore,the steep optimization and detection of the pulse edge are very critical for the time synchronization system,which is the focus of this paper.In this context,the following study content was carried out.(1)Aiming to meet the detection requirements of optical fiber time synchronization system for pulse signals,a balanced photoelectric detector based on transimpedance amplifier(TIA)was designed and implemented.The balanced photoelectric detector uses a TIA at the first stage and a voltage amplification at the second stage.The circuit structure of the detector was optimized and adjusted through the stability analysis of the phase margin and the calculation of the equivalent noise model to enable the balance detector with higher gain and lower noise.The experimental results showed that the detector has a bandwidth of DC-424 MHz,a gain of 80 dB,a common mode rejection ratio(CMRR)of 33 dB at 10 MHz,and a root mean square of electrical noise peak-to-peak value of 10.307 mV.(2)Aiming to meet the requirements of optical fiber time synchronization system for the steep edge of pulse signal,a highprecision pulse shaping module based on LC lumped bandwidth power division circuit and avalanche transistor pulse generation circuit was designed and implemented.A pulse shaping module was developed to solve the problems that in the optical fiber time synchronization system,the 1PPS signal generated by the commercial signal generator has a long rising edge time and there are differences in the transmission lines between the ports,resulting in a large difference in the 1PPS signal.The LC-based lumped bandwidth power division circuit following the pulse signal generator was used to divide the pulse signal into two identical signals,and then the high-precision pulse was generated by the pulse generation circuit based on avalanche transistor.The experimental results showed that the negative pulse amplitude of the pulse shaping module was-4.8 V,the measured falling edge time was 628ps,the pulse width was 5.5 ns,and the time synchronization jitter STD between different ports was 9.3 16ps.To sum up,in this paper,a high-precision pulse shaping module was developed to solve the problems of long rising edge time of pulse signals generated by commercial signal generators and large difference of pulse signals generated by different ports.A balanced photoelectric detector based on TIA was developed according to the demand of pulse signal detection.This research further optimized the steepness of the 1PPS signal edge,and improved the detection ability of the balanced photoelectric detector to the signal,thus providing an idea for improving the time stability of long distance optical fiber time synchronization system. |
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