Baseband Circuit Development And System Performance Test Of Wireless Time Comparison System

With the rapid development of science and technology,many important fields put forward higher and higher requirements for time comparison accuracy.At present,the commonly used high-precision time comparison methods include satellite one-way time comparison method,satellite two-way time comparison method,satellite common view method and optical fiber time comparison method.The accuracy of satellite oneway time comparison method is more than ten nanoseconds.The cost of satellite twoway time comparison method is high,and the satellite common view method needs additional channels to exchange information,and both methods need real-time coordinate calibration,so the high-precision dynamic application is limited.The accuracy of optical fiber time comparison method can reach tens of picoseconds,but its dynamic application is limited.In order to meet the application requirements of local nanosecond time comparison,it is necessary to study a nanosecond wireless time comparison system suitable for short-range mobility.Based on the traditional transceiver technology,the baseband circuit board of nanosecond time comparison system based on the principle of wireless two-way time comparison is studied and designed in this paper,which realizes the function of signal receiving and processing.In time comparison,the two wireless time comparison systems transmit and receive ranging signals through the antenna.Through the data analysis of the received ranging signals,the pseudo range information of the opposite station is obtained.Finally,the clock error of the two stations is calculated by combining with the local pseudo range to realize time comparison.The system is suitable for shortrange wireless time comparison and has the advantages of high portability,low cost and high precision.In order to further enhance the time comparison accuracy of the system,the zero delay technology is raised in this paper,which reduces the time delay change caused by switching to the order of 100 picoseconds,and improves the time comparison accuracy of the time comparison system from the aspect of hardware.Finally,an experimental platform is built to test the function and performance of the system,which verifies the function and performance of the baseband circuit board.The main contents of this paper are as follows:1.In this paper,the research significance and development status of wireless time comparison system is analyzed and expounded,the commonly used high-precision time comparison methods is analyzed and compared.Finally,the overall scheme of wireless time comparison system is designed by using wireless two-way time comparison method.2.The key technology of zero delay in wireless time comparison system is studied.The importance of on-off hardware delay consistency to wireless time comparison system is analyzed.The implementation principle of zero delay technology and the implementation method of AD9520 internal zero delay are analyzed.3.According to the function of the baseband circuit board,the function modules of the circuit board are divided,the wireless time comparison transceiver baseband circuit with FPGA and DSP as the core devices is designed and implemented,the circuit of each function module and the interface between each module are designed,and the communication interface between the main modules is verified,and the processing and debugging of the circuit board are completed.4.Build an experimental platform based on the baseband circuit board to test the function and performance of the system.The hardware Zero Delay experiment,zero baseline power reduction time comparison experiment and short baseline time comparison experiment are carried out respectively.In the hardware Zero Delay experiment,when the signal strength before and after switching on is constant,the change of time delay is very small,the average value is less than 0.05ns;when the signal strength before and after switching on is changed,the change of time delay is less than0.4ns.In the zero baseline power reduction time comparison experiment,when the transmission power is in the range of-37 d Bm ? + 3d Bm,the time comparison accuracy is better than 0.5ns.In the short baseline time comparison experiment,when the distance between two stations is less than 500 m,the time comparison accuracy is better than 0.7ns.The test results show that the baseband circuit board of the wireless time comparison system designed in this paper can achieve nanosecond time comparison.