Research On Precision Time Interval Measurement Technology Based On FPGA

Time interval measurement provides precise time-based coordinates for scientific research,engineering technology and military industry.With the development of science and technology,various fields have higher requirements for the accuracy and resolution of time interval measurement.In order to meet these needs,time interval measurements are transformed from analog to digital.FPGA development platform has been widely used for its fast running speed,strong scalability and short development cycle.This paper reviews the development of time interval measurement theory and analyzes the time interpolation principle.The existing time interpolation method is improved and the time interval measurement method based on FPGA is realized.The time interval measurement method consists of two parts: "coarse" measurement and "fine" measurement.The "coarse" part is implemented in the form of synchronous counter group.This method avoids the clock frequency limitation of the counter due to the cascade mode.The time interval measurement of the "fine" part is realized by two time interpolation methods: clock phase method and delay chain method.In this paper,a FPGA based method of clock phase method is implemented.This method improves the phase shift of the clock according to the principle of clock division.The PLL in FPGA is used to carry out multiple phases shifting for the half clock cycle of the clock,so as to reduce the limitation of PLL finite number of extracts on the time measurement resolution.In this paper,delay chain interpolation time measurement method based on FPGA is implemented.This method uses edge synchronizer to extract the measured signal edge,avoiding the system's multiple sampling processing;the delay processing of the signal is carried out by using the special carry chain in FPGA to solve the problem of unevenness of delay time caused by wire running in delay chain method.The experimental results show that the time-measuring resolution of the clock phase method reaches 165 ps and the measuring range is 12 us.The time measurement resolution of the delay chain method reaches 61 ps and the measurement range is 20.4us.The time interval measurement methods based on FPGA in this paper have high resolution,and the measurement range can be adjusted,and have the advantages of strong extensibility,short development cycle.So they can be applied to some custom time interval measurement instruments and equipment research and development.