Research On Channel Design And Calibration Technique Of High Flatness Oscilloscope

The research of modern electronic science cannot be separated from electronic measurement.Digital oscilloscope measuring signal graphics is a common universal digital measurement and analysis instrument.It is widely used in a variety of industrial measurement and electronic equipment fault troubleshooting and other fields.Obviously,the digital oscilloscope accurately displaying the actual signal is very important.The signal is collected through the digital oscilloscope,before the display needs to pass through the channel conditioning.Therefore,the real information of the signal can not be effectively reflected if the signal is changed unexpectedly due to the conditioning work of the channel part of the digital oscilloscope.This Research designs the oscilloscope high bandwidth adjustment channel,and designs the digital compensation filter to carry on the calibration work to the oscilloscope channel part.In order to design an appropriate compensation filter,we need to "measure" the characteristics of the oscilloscope channel,so we need to first estimate the frequency response of the channel.Then,we need to use the channel characteristics to design the compensation filter to achieve the compensation filter effect.In addition,we also need to correct the signal amplitude to ensure the accuracy of the signal under the dc component.Finally,the synchronization relationship between the data and the trigger is adjusted to ensure the synchronization between the data and the trigger,so that the filtered data can be used to steadily "draw" the waveform.The following are the main research contents:(1)Channel design and frequency response estimationThe bandwidth flatness of oscilloscope channel has a great relationship with the design of analog channel.This subject adopts the method of frequency sweeping test and conditioning channel to obtain the channel amplitude-frequency characteristic curve.Specifically,the amplitude-frequency characteristic of the channel is obtained by adding the frequency sweeping signal with constant amplitude value and known frequency uniform change on the oscilloscope,and meanwhile the amplitude and frequency measuring work is completed in FPGA and recorded and saved.(2)Design of compensation filterAfter obtaining the channel frequency response characteristics,we need to design a digital compensation filter to correct the channel amplitude-frequency characteristics.The ideal spectrum characteristics of the compensation filter can be obtained by using the acquired channel spectrum characteristics,and the filter coefficient of the compensation filter can be obtained by using the inverse Fourier transform.Finally,a FIR filter is constructed to realize the compensation filter.(3)Channel amplitude correction and trigger synchronizationThe amplitude of the channel may have error under the dc signal,so we design the gain error compensation scheme to realize the channel amplitude correction.Due to the digital filtering and other series of digital processing after data collection,there is an outof-sync phenomenon between the data and the trigger signal.In order to display the waveform in real time and steadily,we need to synchronize the data with the trigger signal.