摘要：
In view of the existing phase-difference algorithm's dramatic performance degradation in instantaneous frequency estimation for Linear Frequency Modulation (LFM) signals when Signal-Noise Ratio (SNR) is low,an improved algorithm is proposed based on N-order phase-difference.Firstly,based on phase reconstruction,the adaptive incremental threshold is set up to confirm the frequency ambiguity position for the frequency mutation caused by SNR threshold,and the loop iteration is utilized for interpolation correction.Then,instantaneous frequency is estimated by high-order phase difference by phase jump information,and the iterative reweighed least square method is used for linear fitting.Finally,the idea of selfadaption is introduced to deal with input signals with different frequencies,especially with low frequency.Simulation results show that,compared with existing phase-difference method,the proposed algorithm can keep low computational complexity while improving anti-noise performance,and the lower limit of input SNR requirement reduces by 4 dB approximately.%针对现有相位差分法在低信噪比条件下估计线性调频(LFM)信号瞬时频率性能明显下降的问题,提出了一种改进的基于N阶相位差分法的瞬时频率估计算法.首先,在相位重构的基础上,针对信噪比阈值引起的频率突变问题,设置自适应的累积增量门限来确定频率突变位置,并利用循环迭代进行插值修正;然后,通过高阶的相位差分估计瞬时频率,以充分利用重构相位包含的跳变信息,并采用迭代变权最小二乘的方法进行线性拟合;最后,引入自适应的思想来处理不同频率的输入信号,增强处理低频输入信号的能力.仿真结果表明,相对于现有相位差分法,改进N阶相位差分法在保持低运算量的同时提升了抗噪性能,对输入信噪比的下限要求降低了约4 dB.
