| It is difficult to make a DOA estimation which contains wide range of frequencies,full range of angles and high degree of accuracy in the complex environment.Based on the limitations of conventional array,this paper puts forward the design of the unequal-interval triangular array.In order to improve the performance,the DOA estimation methods based on adaptive noise suppression,frequency direction and platform noise detection are studied.Specific work is as follows:1.The basic principle of DOA estimation is discussed.Then,the application range of beamforming,cross-correlation and cross spectral estimation methods is studied.In this paper,cross correlation method is used to solve the DOA estimation in wide frequency range,and the contradiction between phase ambiguity and direction finding accuracy is solved by using long and short baseline ambiguity resolution method.2.The limitations of conventional array in wide frequency range and wide viewing angle are analyzed.According to the requirement of using a few elements to achieve DOA estimation in wide frequency range,the unequal-interval triangular array is designed for full space and wide frequency direction finding.3.For the unequal-interval triangular array,a method of DOA estimation combining beamforming and cross correlation is designed.The direction finding performance of the array in different frequency bands is analyzed,and the DOA estimation method is chosen reasonably.In order to solve the problem of low precision in low frequency direction finding,the method of adaptive noise suppression is adopted to inprove the DOA estimation accuracy.4.In order to solve the problems that frequency estimation is inaccurate and remove interference generated by platform vibration noise,this paper studys frequency estimation algorithm.Based on the analysis of the near and far field signal characteristics in the complex environment,an algorithm for reducing false alarms is proposed. |
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