Research Of Time-frequency Domain Test Technology Based On VHS-EM

With the development of computer technology，SLI technology and communicationtechnology，the field of instrument technology has changed dramatically.The NationalInstruments Corporation first proposed the virtual instrument based on computertechnology in1986.The virtual instrument is a computer system which is defined by theuser design with virtual instrument panel and test function is achieved by test software.Jilin University Virtual Instrument Laboratory independently developed the virtualintegrated system of electronic measuring instrument(Virtual Electronic MeasuringInstrument Integration System，abbreviated as VIIS-EM)，which adopts bus technologyto integrate hardware and software organically and can be widely used in the collegelaboratory test.The development of science and technology made the traditional signal test can notmeet the requirement of users. The traditional analysis of signal is the time domain andfrequency domain analysis which used the theory of the Fourier transform. But inmodern test, most of the test subjects are non-stationary, non-periodic, non-statistical,and it requires the use of joint time-frequency analysis method which includes short-timeFourier transform, wavelet transform etc. This paper developed a data acquisition cardbased on the platform of the VIIS-EM and put forward the study of time-frequencydomain，which can analysis not only the time domain，frequency domain signal， butalso non-stationary，non-cyclical nature of statistics signal by using joint time-frequencyanalysis function. The function has a broad meaning in the test field.The system includes hardware acquisition part and software analytical processingpart in this subject. Hardware circuit includes signal conditioning module， A/Dacquisition module，bus communication module，parallel processing module. Themeasured signal is adjusted to the A/D input range by conditioning module，then it isconverted to a digital and sent to the host computer for processing. The system uses adual-channel parallel sampling method to improve the sampling rate of the system，andthe front-end uses the high-gain bandwidth amplifier to improve the bandwidth of the input signal. The software part is developed by the graphical programming languageLabVIEW. The acquisition board and bus are communicated by calling the dynamic linklibrary. The time frequency analysis function of the signal processing section usesshort-time Fourier transform and Wigner-Ville transform analysis methods.