Digital Storage Oscilloscope, Digital Filtering And Interpolation Technique

The Digital Storage Oscilloscope is a powerful tool for analyzing and testing various complicated signals. The DSO, in addition to high real-time sampling rate, should provide more specific details of wave analysis. Therefore, it is very important for the Digital Storage Oscilloscope to restore and reconstruct the original signal, and this relies on the application of digital signal processing technology in the DSO. This paper discusses algorithms and realizations on digital technology in the DSO.The design of digital filters is one of the key problems in the DSO. According to the basic principle of FIR Filter, two methods to design FIR Filter have been studied by means of mathematical approach based on MATLAB, which is window function and optimal design. By comparing the results of the two design, we find the optimal design based on equivalent ripple Chebyshev approximation rule has a great deal of advantages including smooth pass band and forbidden band, and narrow transition band in the same order. The simulation shows that the results can meet the requirements very well. The design process based on MATLAB is very simple and practical.This paper also studies the application of interpolation algorithm to digital oscillograph. At high sweep rates, only a few samples of the signals can be on screen. To give the user a reasonable view of the signals and to measure their parameters accurately, interpolation is necessary. The piecewise cubic interpolations, The piecewise linear interpolation, The piecewise nearest interpolation The cubic spline interpolation of several different waveform of the resumption of results have been compared through programming and simulation and the relevant root mean squre error calculated and analyzed. To take into account the actual measured signal of the unpredictability and complexity, and weigh the accuracy and speed, the choice of the cubic spline interpolation is applied when the signal is less than 100 points, when the point of the signal into question is not less than 100 points, the piecewise cubic interpolation is applied. The design process based on MATLAB is very simple and practical.