Design Of Full Digital High Precision Trigger Module

With the rapid development of electronic technology,increasingly complex electrical signals have put forward higher requirements for the capture ability of electronic measuring instruments.Digital oscilloscopes are the most widely used timedomain test instruments.Triggered precision is imminent.The trigger accuracy depends on the technical indicators such as the sampling rate and bandwidth of the oscilloscope.The TIADC parallel sampling technology is the key to increasing the sampling rate of the oscilloscope.With the increase of sampling rate,the traditional analog trigger schemes cannot determine the precise trigger location in the parallel high-speed data streams.At the same time,the trigger accuracy is limited by analog circuit devices.Analog trigger can no longer support the observation requirements of high-performance oscilloscopes under the parallel architecture,while digital triggering is widely used because of its high accuracy and good stability.This thesis designs an all-digital high-accuracy trigger module based on the 20 GSPS high-speed digital oscilloscope under the TIADC parallel sampling architecture,and designs a high-accuracy advanced trigger scheme for the shortcomings of edge triggers that cannot capture complex electrical signals.A relevant test platform was built to test various functions and technical indicators of the all-digital high-precision trigger module,and the test results all met the design requirements.The main work and problems solved in this thesis are as follows:1.An all-digital trigger module is designed.The digital hysteresis comparison method is used to avoid the false triggering caused by high frequency noise.At the same time,the forward carry method is used to process the parallel high-speed data stream,so as to accurately locate the position of the trigger point in the parallel data.In addition,according to the trigger function logic implementation and data flow direction,the trigger module is subdivided into digital trigger comparison module,trigger source selection module,trigger signal generation module,trigger control module,etc.2.Design and implement a high-precision advanced trigger module.The trigger module processes high-speed parallel sampling data in real time based on the all-digital trigger method,and the edge trigger accuracy can reach up to 50 ps.According to different waveform characteristics,design advanced triggers such as edge,pulse width,slope,underamplitude,window and timeout.By filtering the waveform signals that meet the trigger conditions and using the pulse end edge positioning technology for the effective pulses generated,the advanced trigger can find the precise trigger point position in the parallel data,and increase the minimum identifiable trigger time to 400 ps,which enables the high-precision and advanced trigger function.3.A synchronization scheme for inter-board transmission and a trigger offset correction scheme are designed.Based on the separate architecture of acquiring and processing boards,the metastable phenomena in the transmission process between signal boards are studied in depth.Aiming at the problem of trigger jitter caused by the metastable state during the transmission of storage control signals and trigger positioning signals,a corresponding solution is designed to realize synchronous transmission between related signal boards and ensure stable waveform triggering.The trigger offset caused by the response time of trigger module and the drop point operation of each signal processing module is analyzed in depth,and the offset correction scheme is designed to solve the waveform offset problem.The test results show that the trigger accuracy of edge trigger can reach 50 ps,and the trigger resolution of each advanced trigger can reach 400 ps.The trigger system can realize the functions of source switching,mode switching,trigger release and so on,all of which meet the design requirements.