脉冲噪声下基于 NAT 函数的 LFM 信号多径时延估计

针对脉冲噪声环境下无法准确估计线性调频(LFM)信号多径时延的问题,分析非线性幅值变换法抑制脉冲噪声的原 理,设计了一种新的非线性幅值变换函数 P-NAT(piecewise-NAT)函数,证明了任意随机变量经该函数变换后存在有限二阶矩, 提出了基于 P-NAT 函数的 LFM 信号多径时延估计方法。 分别对发射信号和 P-NAT 函数变换后的含噪多径接收信号进行最佳 阶次 FRFT,根据 FRFT 域的峰值位置偏移量和时延的关系,实现 LFM 信号的多径时延估计。 仿真结果表明,该方法在广义信噪 比为 0 dB、噪声特征指数大于 0. 2 的情况下,时延估计归一化均方根误差小于 10 -4 ,适用于低信噪比和强脉冲噪声环境下的 LFM 信号多径时延估计。

Multipath time delay estimation method of LFM signals based on NAT function in impulsive noise

In order to solve the problem that it is difficult to accurately estimate the multipath time delay of linear frequency modulation (LFM) signals in impulse noise environment, this paper designs a new nonlinear amplitude transformation function P-NAT (piecewiseNAT) function, and proves that any random variable has finite second-order moment after transformation by this function, a multipath time delay estimation method of LFM signals based on P-NAT function is then proposed. The optimal order FRFT is performed on the transmitted signal and the noisy multipath received signal transformed by P-NAT function respectively. According to the relationship between peak position offset in FRFT domain and the time delay, the multipath time delay estimation of the LFM signal is realized. Simulation results show that this method is superior to fractional lower order statistics method and myriad filter method in impulse noise suppression, when the generalized signal-to-noise ratio is 0 dB, the normalized root mean square error of time delay estimation is less than 10 -4 . It is suitable for multipath time delay estimation of LFM signals in low signal-to-noise ratio and strong impulse noise environment.