Research On High-Precision Wireless Time-Frequency Synchronization Technology Based On Small Laser

As communications,aerospace,radar,satellite navigation,and other fields have higher and higher requirements for time accuracy,high-precision time and frequency synchronization technology is becoming increasingly important.The current common time-frequency transmission and synchronization technologies can be roughly divided into fiber-based time-frequency transmission and synchronization,satellite-based timefrequency transmission and synchronization,and laser-based time-frequency and synchronization.Compared with the other two methods,laser-based The time-frequency synchronization method is limited by the environment's specific temperature,wind speed,humidity,obstructions and other factors,so it has shortcomings in long-distance applications,but compared to the optical fiber-based time-frequency synchronization method,it does not need to build a fiber channel at the same time,there is no problem of frequency interference based on satellite-based time-frequency synchronization.Laserbased time-frequency synchronization will be promising in short-distance applications in the kilometer range.Therefore,it is very meaningful to study high-precision timefrequency synchronization technology based on small lasers.In the previous work of this research group,a continuous laser-based one-way time-frequency synchronization on an indoor 40 m free space link was realized,and the electrical phase compensation method was used to compensate for the fluctuation of the time signal.However,the time signal transmitted in this experiment has a high frequency and cannot be received and used more widely by other systems,and the result is not universal and general applicability due to factors such as the experimental environment indoors and the short transmission distance.This paper has completed the research on the two-way time-frequency synchronization technology in outdoor 150 m space based on small lasers.The main work and innovations are as follows:(1)A brand-new time information encoding method is proposed.Through this serial time code method,time information and local time interval measurement information are loaded into the standard 100 Hz time signal,and the receiving station obtains it when twoway time-frequency synchronization is performed.Information of the master station.(2)This article uses a combination of coarse measurement and fine measurement to measure the time interval,and uses a combination of coarse synchronization and fine synchronization when synchronizing.Both coarse measurement and coarse synchronization use direct counting methods,while fine measurement uses the CARRY4 carry chain resource inside the FPGA to construct the delay chain by cascading,and send the measured signal into the delay chain to obtain its time interval..Fine synchronization uses the IDELAY primitive to generate a delay chain by providing a reference clock.After calculation,the delay of each stage is about 78.125 ps.(3)A large-scale space laser transmission link of 150 m outdoors was built,and a twoway time synchronization experiment based on a small laser was realized,and the experiment was completed,and the experimental data was obtained.The experimental result shows that the standard deviation of the delay fluctuation after synchronization is524 ps,the time deviation at 1s is 495 ps,the time stability at 1s is 8.58×10^-10,and the time stability at 1000s is 2.72×10^-14.