基于分数阶傅里叶变换的线性调频脉冲信号波达方向估计

DOA Estimation of Wideband Linear Frequency Modulated Pulse Signals Based on Fractional Fourier Transform

针对宽带线性调频脉冲信号的时宽与观测时宽不等的情况,基于分数阶傅里叶变换(FRFT)提出了一种新的中心频率估计方法,并据此对基于FRFT的MUSIC算法的波达方向(DOA)估计进行了改进。该算法利用线性调频信号在傅里叶变换域良好的能量聚集性,分析了脉冲信号中心频率随着脉冲信号在观测时间内位置的变化规律,并修正了中心频率估计的方法。在相应的分数阶傅里叶域,构造分数阶傅里叶域的方向向量,利用MUSIC算法进行DOA估计。数值仿真验证了该算法对方位估计的有效性,并仿真分析信噪比(SNR)和脉冲信号时间宽度对方位估计结果的影响。随着SNR的增大、脉冲信号时间宽度的增加,方位估计方差减小。

A new method for a center frequency estimation based on fractional Fourier transform （FRFT） is proposed for the case that the time width of wideband linear frequency modulated pulse signals is not equal to the width of observation time. The MUSIC algorithm for direction of arrival （DOA） estimation in the fractional Fourier domain is improved. Based on the energy-concentrated properties of linear frequen- cy modulated signal in the fractional Fourier domain, the proposed approach is used to analyze the change of center frequency with the position variation of pulse signal in observation time. And the array manifold vector of fractional Fourier domain is constructed using the MUSIC algorithm for DOA estimation. Numerical simulation shows the effectiveness of the algorithm for DOA estimation. Then the influence of the SNR and time width in observation time on DOA estimated results is analyzed. The azimuth estimation variance decreases with the increase in SNR and the width of pulse signal.