Based On Fractional Fourier Transform Of The Wideband Linear Fm Doa Estimates

Direction of arrival (DOA) estimation has been a significant research area in array signal processing, and it is widely used in radar, sonar, and communication systems. In recent years, the DOA estimation of the non-stationary Linear Frequency Modulation (LFM) signal has received growing attention, and it has been becoming a new hot topic. The Fractional Fourier Transform (FRFT) is a newly developed time-frequency analysis tool which is very propitious for the processing of the LFM signal. This dissertation is focused on the DOA estimation of wideband LFM signal based on FRFT. The main contributions and innovations of the dissertation are:1. A new method based on FRFT for estimating DOA of the wideband LFM signals is presented. In the implementation of the method, the observed signals are first transformed to fractional Fourier domain, and by the unique concentration signature of signal, the FRF domain steering vector is defined, then root-MUSIC is used to estimate DOA of impinging signals in the corresponding fractional Fourier domain. Additionally, the theoretical analysis about the estimate errors are also provided and verified by simulation results thus makes this method more reliable in theory and in practice. Compared with the DOA estimation algorithms based on the WVD, this method avoids Focusing and interpolation, and needs no initial DOA estimation. So this approach has good estimate performance with little computation complexity, and for multi-source, there are no cross-stems.2. In allusion to the wideband LFM signals which have the same time-frequency signatures, an improved method for DOA estimation in coherent signal environment is proposed. In the corresponding fractional Fourier domain, through forward /backward spatial smoothing, the problem of DOA estimation for wideband LFM signals which have the same time-frequency signature is solved. Simulation examples are provided showing the effectiveness of the presented technique.3. Based on the above proposed methods, the two-dimension (2-D) angles estimating of wideband LFM signal in fractional Fourier domain is investigated in detail. By using...