Research And Implementation Of Virtual Oscilloscope Based On FFT Spectrum Analysis Algorithm

Testing technology has been applied to most areas of engineering, which has become an important indicator of productive efficiency and manufacturing capabilities. In order to improve productive efficiency and product performance, lots of countries strived to develop automated testing techniques. But the research on the automatic test system is late in our country, so most of sophisticated testing equipments are imported. Today, the emergence of virtual instrumentation gives us a new opportunity for development.This paper has used DSP technology and virtual instrument technology to construct the signal processing and analysis system. It is the virtual oscilloscope module of helicopter automatic test system. The structure this paper has applied is different from the common structure of virtual oscilloscope. To avoid problems with large data transmission, the DSP module completed both data acquisition function and data processing function. It also improved real-time performance of the system.This paper focuses on digital signal processing and analysis theoretics, and their implementation on the DSP module. On the aspect of digital filtering, MATLAB tools are applied to design Kaiser window FIR low-pass filter, and optimize the parameters to reduce the Gibbs phenomenon, in order to obtain accurate information on the sampling signal. On the aspect of spectrum analysis, the causes of the energy leaking problem for FFT analysis are analyzed. The method of additional Hanning window FFT algorithm is applied to suppress the energy leakage, but experiments show that the error is still large. In order to rectify the results of the FFT spectrum, many methods are studied, such as interpolation correcting method and FFT+FT method. Both experimental results were analyzed and compared, and the difference of the two algorithms was studied. The reasons of error by the two algorithms are also given out. On the aspect of the realization for signal analysis algorithms, IQ data format is used to complete a high-precision floating-point operations on the fixed-point DSP.In this paper, DSP module is applied to test the current signal of the motor. Test results show that the DSP module was still able to maintain high accuracy in the environment of strong electromagnetic interference.