Research On High-precision Time Interval Measurement Based On SAWF

High-precision time interval measurement is essential in aerospace,industry,daily life,and many other fields,especially ps-order time interval measurement which has been widely used in science and technology projects,such as laser and radar speed measurement,high-speed charged particle flight orbit determination,precise satellite navigation and positioning and space-ground gravitational wave detection that developed by many countries.However,ps-order time interval measurement in the domestic now available is confined with device performance,measurement methods and system's design and so on,it is mostly urgent to improve the measurement precision and resolution.This paper describes a ps-order time interval measurement method based on surface acoustic wave filter(SAWF).This measurement system contains five sub-modules,which are respectively narrow pulse unilateral-capturing,SAWF excitation,A/D clock sampling,data storage and transmission and digital signal processing algorithm.The specific design idea is as follows: firstly,we use a narrow pulse signal which is generated by the narrow pulse unilateral-capturing module to excite the SAWF to output its excitation response signal.Evidently,this response signal has a high suppression spectrum outside its narrow frequency band.Then,the two periodic excitation responses are sampled at the clock cycle,which demand accurate reconstruction from a limited number of samples.Finally,we will take advantage of correlation algorithm to obtain an estimation,and further compare and determine the time interval between the two excitation responses.In this system,we use SAWF as a time-interpolation filter,and its excitation response can be used as a time-interpolation signal,which can play the role of stretching the time and converting single measurement to multiple measurements.In the processing of the sampled data,we combine digital signal processing for quadratic correlation.Because of the average effect of the correlation operations,it is possible to largely eliminate the additional noises in two mutually independent ways,reduce the noise floor,improve the sensitivity and other important indicators,which can greatly reduce the measurement errors and ensure high-precision and high-resolution time interval measurements of this system.The results of system simulation and practical measurement have shown that this method can achieve 2.48 ps measurement precision and better than 0.1 ps measurement resolution.