Research On Random Equivalent Sampling Method For High Speed Signal

With the rapid development of modern digital signal processing technology, more and more high speed signals are sampled. Random equivalent sampling is not restricted by the Nyquist sampling theorem, and it can use lower sampling rate to achieve higher equivalent sampling rate, which significantly reduces the complexity and hardware cost of sampling system, so it is widely used in various fields of high speed signal acquisition and processing. The existing random equivalent sampling has the problem of the larger short time measurement error between the trigger point and the first sampling point after the trigger point, and the problem that the real-time and the accuracy of interpolation cannot be satisfied at the position points that are not sampled in the waveform, therefore, the research on random equivalent sampling method for high speed signal is carried out. The work done in this paper is mainly divided into the following aspects:Firstly, This paper analyses domestic and foreign research present situation and the basic principle of the random equivalent sampling, and expounds in detail the short time measurement principle, sampling the data sorting principle and signal waveform interpolation display technique.Secondly, a short time measurement algorithm based on time identification is proposed. Aiming at the problem of low precision of short time measurement in the existing random equivalent sampling, a time discrimination FPGA circuit based on edge detection and narrow pulse propagation is constructed, which is used to extend the short time so as to meet the measurement requirements; in order to improve the accuracy of measurement, a measuring time circuit is designed, which is used to transform the measurement of time into the measurement of voltage. The test shows, this method has the advantages of high measurement accuracy and simple circuit design, so this method meets the requirement of the short time measurement of random equivalent sampling.Thirdly, a linear interpolation algorithm based on weight function is proposed. Aiming at the problem of the large interpolation error in existing linear interpolation algorithm, although it can meet the requirement of real-time interpolation, the linear interpolation function of the interpolation interval is combined with the linear interpolation function of the adjacent interpolation interval by designing a weight function, so that a weighted linear interpolation function is constructed in the interpolation interval. Experimental data analysis shows that compared with the two order Lagrange interpolation algorithm, this algorithm improves the accuracy and real-time performance of the interpolation algorithm.Finally, the improved prototype of the portable Ethernet eye test equipment is developed. By improving the hardware and software platform of the existing portable Ethernet eye testing equipment based on real-time sampling,random equivalent sampling method is implemented. Fast Ethernet are respectively tested by the improved prototype and the existing equipment, the test shows that the improved prototype can more accurately realize the sampling of Fast Ethernet.