Design Of Full Digital Trigger Module In High Speed Digital Oscilloscope

With the continuous development of electronic technology in the new era,electrical signals in electronic systems become more complex and special,which puts forward higher requirements for the acquisition ability of electronic measuring instruments.Digital oscilloscope,as the most widely used time domain testing instrument in the field of electronics,can accurately capture signals with complex characteristics by the trigger function.In recent years,the sampling rate,bandwidth and other technical indicators of oscilloscope continue to break through,and the trigger system also needs to constantly update to match the high-speed acquisition module.In the case of high sampling rate,due to the limitation of FPGA internal working clock,there are multiple sampling points in each working clock cycle,but the traditional analog trigger scheme cannot determine the exact position of the trigger points.At the same time,temperature,noise,device and other factors will lead to the comparator output instability and trigger jitter.And the difference between the waveform data acquisition and storage path and the analog trigger circuit path will introduce systematic deviation to the analog trigger.To sum up,the analog trigger can no longer meet the user’s observation requirements under high-speed digital oscilloscope.In order to improve the precision and the ability to capture trigger of trigger system,this thesis takes high-speed digital oscilloscope as the application scenario to design the full digital trigger module,and give a feasible solution to the key problems in the system design.Finally,these functions are verified on the machine.The main work and problems solved in this thesis are as follows:（1）Scheme design of full digital trigger system.Taking the sampling data as the trigger source signal,a digital trigger module is designed to judge and process the parallel sampling data.Which avoids the systematic deviation caused by the difference of signal acquisition path and trigger path.The trigger system is divided into trigger comparison module,trigger source module and trigger control module according to the function,which improves the modularization of the trigger system.For edge trigger,the offset error of trigger position is analyzed and the corresponding correction scheme is designed.（2）Design of advanced trigger module.The trigger mechanisms of different advanced trigger modes are deeply analyzed.Based on the high-speed digital oscilloscope platform,the parallel trigger schemeis designed for pulse width trigger,slope trigger,runt trigger,set-up time and hold time trigger to deal with different acquisition conditions.It greatly improves the oscilloscope’s ability to capture complex signals,increases the step of the advanced trigger measured parameters to 800 ps.（3）Design of trigger coupling function scheme,a scheme of trigger coupling for digital trigger source signal is designed to replace the original analog trigger coupling scheme.The digital trigger source signal is passed through the real-time filter to eliminate the noise in the trigger signal and avoid the wrong trigger.Finally,the full digital trigger module is applied to high-speed digital oscilloscope,and the related test platform is built.Through the debugging and testing of the digital oscilloscope,the functions and technical indexes of the full digital trigger module designed in this thesis all meet the requirements,the research objective was accomplished.