Design And Test Of High Speed Signal Acquisition System

The high-end oscilloscope can play an important role in the R & D,production and maintenance of electronic units in aerospace and aviation equipment,such as communication,radar,navigation,avionics,computer and so on,and provide the core basic instrument support for the function,performance test and evaluation of these electronic equipment.The research content of this subject is a sub-project of "Development and Application of 20GSa/s Broadband High Speed Multifunctional Oscilloscope".It is responsible for the research of 20GSa/s High Spe ed Signal Acquisition and Calibration Technology,Real-time Digital Downconversion Technology,High Speed and Large Capacity Storage Technology.The research content of this topic is the key technology of high-end Oscilloscope,which can be used as high-end Oscilloscope.Firstly,starting with the overall working principle of the oscilloscope,this paper studies the overall hardware scheme of the key component 20GSa/s high-speed signal acquisition module,introduces the role of the high-speed signal acquisition module in the whole machine,the interaction with other components,the composition of internal functional units and the main functions of the module.Aiming at the functional and performance requirements,the key components such as ADC,FPGA and clock on the module are given.Finally,the requirements of engineering design are introduced,including three-dimensional design,six-dimensional design and software engineering design.This paper focuses on the key technologies involved in high-speed signal acquisition module,namely high-speed signal sampling and calibration technology,real-time digital down-conversion technology,high-speed and large-capacity storage technology.In the aspect of high-speed signal sampling,20GSa/s sampling is realized by 4 pieces of 5GSa/s ADC cross-sampling.The key points of high-speed cross-sampling are analyzed,including clock circuit design,ADC design consideration and data calibration.In the aspect of clock design,the selection of reference clock,the comparison of clock circuit schemes and the design of clock circuit are studied.A small size,low power consumption and low cost high performance dedicated clock chip scheme is adopted.In data calibration,the calibration work is carried out from four aspects: offset calibration,ADC data misalignment calibration,phase calibration and gain calibration,and the calibration process is given.According to the characteristics of application requirements,this paper presents a real-time digital down-conversion technology architecture,which consists of digital orthogonal mixing,FIR1-FIR3 filter and HB1-HB10 filter.After that,each functional unit is analyzed in detail,and the implementation architecture is given.For FIR and HB filters,the optimal filter order and its amplitude-frequency response curve are given.High-speed and large-capacity storage technology is analyzed from three aspects: memory selection,circuit design simulation and memory control.Compared with many kinds of memory,DDR3 memory is selected.In the end,this paper tests and validates the work carried out,introduces the environment and process of test and validation evaluation,and describes the methods of index test and validation evaluation.In the aspect of 20GSa/s signal acquisition index,the sampling rate and effective resolution index are evaluated;in the aspect of real-time DDC,a symbol rate is selected for EVM evaluation according to 13 I/Q rates through vector signal analysis software;in the aspect of high-speed and large-capacity storage,the error rate,writing efficiency and reading efficiency index are evaluated.Through the evaluation,all the indicators meet the requirements of the subject indicators.