The Design And Implementation Of Portable High-Speed Data Acquisition And Waveform Reconstruction System

With the rapid development of digital system,ultra-high-speed data stream has become a major feature of modern digital systems.With the rising frequency of the signals,the front-end digital systems need to use high speed or ultra-high-speed data acquisition system to sample the signal and achieve the transmission of the signal.With more and more applications,such as fieldwork space and equipment production sites hope that the signal acquisition system can directly reconstruct the original signal in order to observe and analyze the signal in further.Thus portable data acquisition and waveform echo system will have a certain develop space.The paper designed and implemented a high-speed data acquisition and waveform echo system with simple hardware,high stability,high accuracy and low power consumption.It includes the completion of the hardware platform designing and Verilog HDL programming.The design uses the structure of FPGA and random equivalent sampling to achieve not only high-speed sampling,but also reconstruct the original signal directly.The main contents of this paper are as follows.Firstly,analyzed the existed data collection methods and determined the data acquisition scheme for the system: use real-time sampling when the signal frequency is low and random equivalent sampling when the frequency is high.Real-time sampling can directly restore the original signal without additional processing of the sampled data.While random equivalent sampling requires a certain trigger sampling process and signal processing process to achieve the reconstruction of the original signal,so the design will focus on the achievement of random equivalent sampling.Using AD chip with moderate sampling rate can reach high equivalent sampling rate through random equivalent sampling,which not only reduces the difficulty of realization,but also avoid the using of GSPS level of sampling rate that would bring crosstalk,interference,jitter and other phenomena that would affecting the stability of the system.Then introduced the two key technologies of random equivalent sampling: short-term measurements and waveform reconstruction.Introduced the existed short-term measurements and its strengths and weaknesses,so that can be comparing with the time-measure method using in this design and highlight its advantages eventually.Then develop the hardware platform based on the designed data collection scheme.The system uses FPGA as the main controller and the operator to coordinate the work of the system,and complete the controlling and data exchanging of each module,and both achieve random sort algorithm.Then use the comparator,AD sampling chip,DA converter chip as the cores to complete the detailed diagram design of the trigger circuit,digital to analog converter and analog to digital conversion module respectively.Give detailed design of power supply module and the PCB layout.Then divide the system into more specific modules,and introduces the principle of each module.To achieve random equivalent sampling,here use Verilog HDL to realize the modular structure and complete the programming of trigger shaping module,short-term measure module and waveform reconstruction module.At the same time,using the embedded logic analyzer Signal Tap II to analysis important signals of each module and tell the implementation method and process of each module combine with simulation results.Among them,the short-term measurement module uses a novel method,called state method to achieve nanosecond measuring accuracy without any additional hardware.Moreover,optimize the random sort algorithm when realize the waveform reconstruction which improve the performance of the system.Therefore,the new time measuring method and the optimized random sort algorithm is the two bright spots in this paper.Finally,by providing an input to the system and carries on the sampling,then use the oscilloscope to observe the reconstructed waveform can verified whether the system can satisfy the requirement of the system indicators or not.Last concludes this paper and points out the shortcomings of the design,and prospect the specific work of the next phase in order to improve the system.