Design Of Mixed Trigger System Of Oscilloscope

With the rapid development of electronic technology, higher requirement of electronic measuring instruments is also put forward. In the process of information acquisition of digital storage oscilloscope, the trigger is lead up as an important indicator of system to collect right data and display waveform steadily. The traditional trigger patterns will increase investment costs and consume a large amount of time in dealing with the complicated signal or other synchronal detection of mixed signal, so it requires a more advanced triggering mechanism.The main task of the topic is to complete the design of mixed trigger system of oscilloscope. The hardware platform is based on the mixed signal oscilloscope, realized synchronous acquisition of mixed signal such as analog and digital; trigger system is the most important part of the process on mixed signal acquisition. The main contents of the research include:(1) Mixed trigger system. High speed and mixed trigger are the key technology of this design to meet the needs of synchronous display of mixed signal such as analog and digital. In the process of sampling digital and analog signals, while triggering and detecting the mixed signal. Analog trigger source is to be compared with comparative level that produces trigger pulse. Digital trigger source is to be compared with threshold level that produces digital pulse. They were sent to trigger system of the oscilloscope and logic analyzer, then users select trigger modes, through detection and recognition and trigger conditions judgment, finally output a trigger signal. output eventually trigger output signal crossover to the other side of the trigger system again choose to implement a mixed triggering.(2) HDTV triggers circuit. It uses decoder chip to translate the HD analog video signals into four kinds of digital synchronous signals which include vertical synchronous signal, odd and even field signal and horizontal signal. Then put four kinds of triggers signal into the corresponding trigger module as the judgmental condition of optional trigger based on the input video formats. Trough hardware language on FPGA to generate odd field trigger signal, even field trigger signal, the specified row trigger and any line trigger signal,(3) Design of acquisition and trigger synchronization control. The design is based on FPGA which uses hardware to fix the trigger point. The two designs were compared and analyzed in this paper. One is using trigger point synchronizing on pulse expanding circuit, expanding the duration of the pulse that is less than the quantization unit into for digitized measurements, this design will reduce the trigger point jitter and achieve the purpose of displaying the waveform stably in acquisition; the second uses the integrated LVDS receiver(IP) on FPGA to realize the acquisition of synchronization trigger, the output differential signal of ADC and output trigger pulse of comparator are sent to the receiver for desterilizing, the scheme solves the trigger delay of channels, reduces the external trigger jitter, achieves the precise positioning of the trigger point.The designer of trigger system in this paper realizes the flexible and reliable trigger of the mixed signal, and realizes the multi trigger mode of high definition video. The precise location of the trigger point is realized by the trigger synchronization process.