DOA Estimation Analyse Of LFM Signal Based On The FRFT

Direction of Arrival (DOA) estimation has been a significant research area in array Signal processing. The DOA estimation of the non-stationary Linear Frequency Modulation (LFM) signal has been becoming a new hot topic and it has been received growing attention in recent years. With good cross-terms reduction and high time-frequency resolution, the Fractional Fourier Transform (FRFT) has been considered a linear and full time domain analysis tool for non-stationary signal processing. For a newly developed time-frequency analysis tool,it has been widely used in the multi-component LFM signal processing for its perfect property. Combining the FRFT with array Signal processing,the DOA estimation of LFM signal is discussed based on the FRFT in this thesis.1,We presented the definition of FRFT and some basic characteristics, and analysis a discrete algorithm. Then the energy distribution of Gaussian white noise in the FRFT domain also is discussed.2,Analyze some classic algorithm for the DOA estimation. We establish signal reception model firstly, then the Delayed-add and Minimum Variance Distorionless Response (MVDER) estimation algorithm have been discussed for the narrowband non-coherent stationary signal source, compare this two algorithm we can get that the resolving power of the MVDER algorithm's is better than the Delayed-add algorithm. Further more, anther two methods for DOA estimation are discussed: Multiple Signal Classification (MUSIC) algorithm and Generalized Eigenvalues utilizing Signal subspace Eigenveetors (GEESE) algorithm. In the same condition, the resolving power of MUSIC and GEESE algorithms are better than Delayed-add and MVDER algorithm. But all these algorithms can not estimate the DOA when signal is non-stationary LFM signal. We also discussed the influence for MUSIC algorithm performance when the number of array is different. Simulation results proved that3,According to the time-frequency properties of LFM signal, we have analyzed some properties of LFM signal in the FRFT domain, consider the LFM signal in certain fractional Fourier domain can take on energy concentration property, and the phase relationship between the received signal of received array element, the time-invariant direction matrix in that FRFT domain is derived,then the signal direction can be estimated by the MUSIC and GEESE algorithm, GEESE algorithm has a low complexity. The simulation results show that the algorithm can effectively estimate the signal direction even in a low Signal to Noise Ratio (SNR).