Research On Reducing The Sampling Rate Based On Time Interleaved Acquisition Technology

With the attention to shallow geology and the rapid development of geophysical technology,the research on shallow surface detection has entered the white-hot stage.Among amounts of shallow surface detection methods,frequency domain electromagnetic detection is widely used in geology,national defense,military and other fields for its wide detection range,fast response and high detection accuracy.In order to compromise the contradiction between sampling rate and sampling accuracy in the broadband electromagnetic induction detection system independently developed by Jilin University,the solution of reduced sampling rate,based on frequency domain electromagnetic detection method,is adopted in this paper,which performs better than the solution of single A/D conversion chip in dealing with the contradiction.During the completion of the thesis,the research and realization of time-interleaved sampling technology is studied to solve the contradiction between high sampling rate and high sampling speed.Specifically,the time-interleaved sampling technology adopts multiple A/D conversion chips to sample the same signal at different time intervals,and achieve equivalent sampling rate,which is several times that of a single-chip A/D conversion chip,by recombining and splicing the collected data from different A/D conversion chips.Based on the theory of clock phase separation technology,the technology of all-digital phase-locked loop is researched,which can satisfy the requirements of the time-interleaved sampling for the phase-shift clock.Based on the time-interleaved sampling technology,a time interleaved acquisition system prototype has been designed and developed in this paper.The sampling system consists of three parts: the signal conditioning unit,the time interleaved sampling unit and the data acquisition unit based on FPGA.Taking FPGA as a platform,this paper studies the conversion,storage and transmission of data collected from the sampling system prototype based on time interleaved sampling technology.By data width matching,building FIFO and the transmission rate matching,we have solved the problem that may occur during data transmission.Besides,we use spectrum analysis to estimate the error,and take measures to compensate the error of the system.The performance of the high-speed sampling system based on time-interleaved technology was tested in the end.Firstly,the simulation test,the actual test and the spectrum analysis were carried out for the four-channel sampling clock.The results obtained satisfied the requirements of the time interleaved acquisition for the clock.Next,the noise test and the sine wave test were conducted for the sampling system.Finally,combined testing is performed under laboratory conditions in conjunction with the original system.