12.5GSPS Oscilloscope Module Calibration And Software Design

Oscilloscopes have become one of the important electronic test instruments,and its main functions include signal waveform display,parameter measurement and data storage.Virtual oscilloscope is mainly composed of acquisition board and corresponding computer software.The combination of high-speed data transmission of hardware and flexible data processing of computers makes the application scenarios of oscilloscope more diverse and the test system runs more efficiently.Due to the existence of systematic errors in the design of the acquisition module,the actual sampling results are inconsistent with the theoretical values.In order to improve the system performance,it is necessary to correct the error of the acquisition system.According to the different domains of correction methods,correction methods can be divided into analog domain correction and digital correction.However,the analog calibration method usually requires additional calibration circuitry,which increases the area of the capture board.The method of digital calibration or analog and digital mixed calibration has the characteristics of flexibility and high efficiency,which can meet the calibration requirement.In this thesis,the design of instrument driver and general oscilloscope panel based on the oscilloscope hardware is completed first,and the basic test function of oscilloscope is realized.Error analysis and calibration of analog channels and time-interleaving ADC（TIADC）are also presented.The details are as follows:1.Design of Oscilloscope Software.First,the instrument driver is designed based on IVI protocol,and then we also designed the oscilloscope subsystem,which mainly includes channel sub-module,trigger module,level module and acquisition module.Second,the design of general oscilloscope panel based on Qt is completed,and the functions of waveform display,parameter measurement and parameter selection are realized.2.Calibration of Signal Conditioning Channels.First,we analyzed the error of the signal conditioning channel,and then a combination of digital and analog methods were used to correct the channel’s zero error,offset error,and gain error.In order to improve the calibration efficiency,the automatic calibration thread is introduced to complete the automatic correction of channel errors.3.Estimation and Calibration of TIADC Mismatches.Based on the error analysis of TIADC technology used by the acquisition module,the sinusoidal fitting method is used to estimate the system error,and the estimation performance is improved under the condition of under-sampling.The perfect reconstruction method is discussed in this paper because the traditional digital correction method is only suitable for narrowband input signal.It can be used to complete the correction of wideband signal.The oscilloscope application software containing above can realize the basic test function of oscilloscope.The experimental results show that the error range of the calibration system meets the requirement.