基于FRFT的对称三角LFMCW信号检测与参数估计

Detection and Parameter Estimation of Symmetrical Triangular LFMCW Signal Based on Fractional Fourier Transform

对称三角线性调频连续波(STLFMCW)信号是一种典型的低截获概率雷达信号。该文通过分析STLFMCW信号在分数阶Fourier变换(FRFT)域的频谱分布特征,发现STLFMCW信号包含的各段LFM信号在其对应的"最佳"FRFT域内具有很好的能量聚集性;各段LFM信号在频域内会完全重叠,叠加的频谱幅度较高,在低信噪比条件下,严重影响STLFMCW信号的检测与参数估计。因此,利用FRFT检测STLFMCW信号时,必须克服该问题。该文提出一种FRFT与聚类分析相结合的STLFMCW信号检测与参数估计方法。该算法解决了由STLFMCW信号的频谱叠加给信号检测带来的问题,而且,克服了信号尖峰的高度必须高于噪声幅度的限制,在低信噪比条件下具有较好的检测效果。最后,仿真验证了该方法的有效性。

The Symmetrical Triangular Linear Frequency Modulated Continuous Wave（STLFMCW） signal is a sort of typical Low Probability of Intercept（LPI） radar signal.The spectrum distribution characteristics of the STLFMCW signal is analyzed in the FRactional Fourier Transform（FRFT） domain.It is discovered that the each segment of Linear Frequency Modulated（LFM） signal contained by the STLFMCW signal has an energy peak in its ＂optimal＂ fractional Fourier transform,and the spectrum of all the LFM signal segments contained by the STLFMCW signal folds together completely in the Fourier domain,so the amplitude of the spectrum is very high.It badly influences the detection and parameter estimation of the STLFMCW signal on the low SNR condition.Therefore,this problem must be solved when FRFT is used to detect the STLFMCW signal.A novel method is presented to detect STLFMCW signal and estimate its parameters based on the FRFT and clustering analysis.The method solves the problem brought by the spectrum folding of the STLFMCW signal,and this method overcomes the limit that the peaks of the STLFMCW signal must be higher than the amplitude of the noise.On the low SNR condition,this method still has better effect to detect STLFMCW signal.Finally,simulations verify the effectiveness of the method.