Research Based On Time-Frequency Distribution Of LFM Signal And Simulink Of Fractional Fourier Transform

By analyzing the LFM (linear frequency modulation signals) the time-frequency distribution, Wigner-Ville distribution, Wigner-Hough distribution, combined with FRFT (fractional Fourier Transform) and time-frequency distribution of the above, to be used FRFT fractional Fourier domain Filtering possible, and through the use of simulation matlab FRFT to the superiority of LFM signal filtering.This article introduced the basic concept and the application of linear frequency modulation signal, and through analyzes the time-frequency distribution of LFM (linear frequency modulation signal), the Wigner-Ville distribution, the Wigner-Hough distribution, combined with FRFT (fractional Fourier Transform) and time-frequency distribution of the above, obtain the possibility of using FRFT fractional Fourier domain Filtering, when carries on the LFM signal filtering using FRFT, the most main merit is that it got rid of the Wigner-Ville distribution, the question of the Wigner-Hough distributed disturbance and secondary secondary ,according to the Lohmann fundamental research ,it has derivated that the Wigner-Ville distribution (WVD) of FRFT is the rotation of axis form of WVD coordinate of original signal, carries on WVD to the chirp signal in the article is possible to see the time-frequency accumulation (approximately is a straight line); Third, through compare with the Wigner-Ville distribution ,the W-H transformation have the two merits: The noise elimination and the cross term, carry on the W-H transformation to the WVD of chirp signal is possible to see the better time-frequency accumulation of LFM signal. Fourth, uses the FRFT to establish the two-dimensional surface, chooses the narrow bandpass filter to carry on the filter, obtain the signal of after filter. Carries on FRFT to the signalof after filter, then replies the chirp signal of the primitive input. It discovered that the signal-to-noise ratio distinct enhancement thought compare. In summary, carries on the LFM signal filtering using FRFT has its unique and convenient superiority compared with other methods,it has certain value of practical application.