| Linear frequency-modulated (LFM, chirp) signal that is often applied in radar, sonar and communications system is nonstationary signal, in which the frequency varies with time. Since Fourier analysis, which is a transform in full-time domain, can't describe the signal property in time-frequency domain, Fractional Fourier transform becomes one of the new time-frequency analysis theories now. Fractinal Fourier transform is Fourier transform in broad sense, which is the representation of the signal in Fractional Fourier domain. As optical equipment carry out Fractional Fourier transform easily, the application of Fractional Fourier transform in optical signal processing come true first. With the presentation of Digital computation of Fractional Fourier transform, it has begun to apply to electric signal processing.On the basis of study of Fractional Fourier transform and its digital computation, the main aim in this paper is to study the applications of Fractional Fourier transform in LFM signal detection and parameter estimation, to research filtering of LFM signal in the Fractional Fourier domain and the digital image watermarking in the Fractional Fourier domain. In this paper, we set up a model for LFM signal detection and parameter estimation, present the iterative method applying to LFM signal detection, found a model for filtering of LFM signal and improve the method of the digital image watermarking in the Fractional Fourier domain. The main content includes:1. Study the general theory of Fractional Fourier transform2. Analyze the method of Discrete Fractional Fourier transform and its digital computation3. Set up a model for LFM signal detection and parameter estimation on the basis of realization of the digital computation of Discrete Fractional Fourier transform4. Found a model for filtering of LFM signal in the Fractional Fourier domain5. Improving an application of the Fractional Fourier transform in the digital image watermarking... |
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