Virtual Instrument Software System Of Spectrum Analysis

Continuous spectrum analysis in discrete spectrum correcting technology and software system are presented in this thesis. The study is based on the project of National Natural Science Fund of China and the State Ministry of Education of China, which deeply research on spectrum correcting technology in dynamic signal analysis and developing dynamic signal analysis virtual instrument software system.As response signal of damped free vibration could be considered as product of the harmonic wave and the unilateral exponential function and the rectangle window, the peak frequency and phase are frequency and phase of the harmonic wave signal is proved in theory in this paper. The variety of sampling frequency, error of frequency, damping, phase, which affect the precision of the amplitude of discrete spectrum of damped free vibration signal is analyzed, and we present a new method of getting the recovery coefficient for amplitude of unilateral finite length exponential window, which rebuilds a new signal with the damping, frequency, phase that have been estimated and then by DFT, we can get the coefficient. When the error of the estimated frequency is zero, the error of amplitude is minor. Theory and simulation show the variety of sampling frequency, error of frequency, damping, phase affects the precision of amplitude severely, and the effect of the variety of one parameter is restricted by the other. When the ratio of the frequency of the signal and the sampling frequency is within 0.25 and 0.4, and the damping is within 0.005 and 0.02, no matter how large the error of the frequency is, the amplitude still has a high precision, the maximum error of amplitude is less than 5%. When one frequency is very close to the others, this method can not be used.This thesis also study on the method of high speed data acquisition based on windows2000, the application of multithreading in dynamic signal analysis virtual instrument software system programming by Visual C++. Adopting the latest research result on dynamic signal discrete spectrum analysis and the idea of virtual instrument, a dynamic signal analysis virtual instrument software system is developed, which is based on windows and has good performance.