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线性调频(LFM)信号目标的方位估计是水声探测研究的重要内容,在进行方位估计时,若存在强干扰信号源与强背景噪声,阵元接收信号的信噪比会显著降低,严重影响LFM信号目标方位估计结果的准确性.针对该问题,提出了一种简明分数阶滤波方法,并将其与常规波束形成方法(CBF)相结合来实现低信噪比条件下LFM信号目标的方位估计.简明分数阶傅里叶变换能在正交角度上将LFM信号的能量聚集在特定频点处并形成明显的能量峰,利用该特性,可对阵列各阵元接收的低信噪比LFM信号在简明分数阶域聚集的能量峰进行最佳滤波,以滤除干扰信息及背景噪声.对滤波输出进行逆简明分数阶傅里叶变换可得到增强信干比和信噪比的阵元域信号,进一步用于目标方位估计,就能获得更加准确的目标方位。数值仿真结果和海试实验数据处理结果验证表明,本文所提出的方法可有效抑制干扰和背景噪声,并对低信噪比LFM信号进行准确、稳健的方位估计。
The azimuth estimation of linear frequency modulation (LFM) signals is an important part of underwater acoustic detection. When there is a strong interference signal source and strong background noise in the azimuth estimation, the signal-to-noise ratio of the received signals of the array elements will be significantly reduced This paper proposes a simple fractional filtering method and combines it with the conventional beamforming method (CBF) to achieve the target position of LFM signal under low signal-to-noise ratio Estimation.Factory fractional Fourier transform can gather the energy of LFM signal at a certain frequency point and form the obvious energy peak at the orthogonal angle.Using this characteristic, the low signal-to-noise ratio LFM The signal is filtered in the energy peak concentrated in the fractional order domain to filter the interference information and the background noise.An inverse concise fractional Fourier transform of the filtered output can be used to obtain the array field with enhanced signal-to-interference ratio and signal-to-noise ratio Signal, further for the target position estimation, you can get a more accurate target position. Numerical simulation results and experimental results of seafaring experiments show that the proposed method can effectively suppress the interference and background noise and make accurate and robust bearing estimation for LFM signals with low signal-to-noise ratio.