基于部分相关的LFM脉冲全参数估计

Whole parameters estimation for linear frequency modulation pulse based on partial correlationtle

针对线性调频(LFM)脉冲信号的侦察问题,提出了调频率、中心频率、信号到达时间、脉宽全套参数集的估计方法。首先,使用分数阶傅里叶变换(FrFT)对信号的调频率与时频关系进行估计;紧接着选取部分相关脉冲对信号进行积累,利用自相关处理完成中心频率、信号到达时间、脉宽参数的估计;然后推导了估计参数的克拉美劳下界(CRLB),分析了信噪比对估计误差的影响;最后分析了部分积累脉宽对估计误差的影响,给出了积累脉宽的选择范围。仿真分析表明,调频率估计误差几乎达到CRLB,在信噪比0 dB、基带与调制参数均未知的条件下,中心频率估计均方根误差约为10^(-1)MHz数量级,信号到达时间和脉宽估计均方根误差约在10^(-1)μs数量级。参数估计误差受到相关脉冲宽度的影响,随着相关脉冲宽度的增加,估计误差呈现先减小后增大的趋势。所提方法特别适用于脉压、合成孔径等新体制雷达的侦察。

Focusing on the reconnoitering problem of Linear Frequency Modulation （LFM） pulse signals, a method to estimate the whole parameters containing frequency modulate rate, center frequency, time of arrival and pulse width, was proposed. Firstly, frequency modulate rate as well as time-frequency relation was estimated based on Fractional Fourier Transform （FrFT）, then partial correlation pulses was used for signal accumulation, at last the autocorrelation technology was used to estimate the center frequency, time of arrival and pulse width. The Cramer-Rao Low Bounds （CRLB） for the parameters were derived and the effect on estimation error caused by signal to noise ratio was analyzed. Finally, the effect on estimation error caused by the width of partial accumulation pulse was analyzed, and some advice was given on choosing the width of accumulation pulse. Simulation results show that the estimation error of frequency modulate rate is close to CRLB. When signal to noise ratio is 0 dB without any knowledge of baseband and modulation parameters, the Root Mean Square Error （RMSE） of center frequency is about 10-1MHz orders of magnitude, and the RMSE of time of arrival as well as pulse width is about 10-1 μs orders of magnitude. The estimate error, which is affected by the correlation pulse width, decreases with the increase of correlation pulse width, and then increases. The proposed method is especially applicable to the reconnoitering of new system radar such as chirp radar, and Synthetic Aperture Radar （SAR）.