基于直接相位差分的LFMCW雷达加速运动目标参数估计

Parameter estimation of accelerating target based on direct phase difference method in LFMCW radar

针对LFMCW雷达中加速运动目标在跨距离单元走动情况下韵参数估计问题,提出一种直接相位差分方法。该方法通过对二维差拍信号沿慢时间维进行直接相位差分,在消除了快、慢时间线性耦合项的同时实现了慢时间维相位的降阶处理。对差分后的信号进行二维FFT运算,根据其二维谱峰位置即可获得目标加速度的估计,同时还可以获取目标速度的粗略估计。根据估计值构造补偿函数分别对上、下调频差拍信号进行补偿,通过解耦合处理即可获得目标初始距离和初始速度的精确估计。详细分析了方法的性能,包括加速度分辨率、最大不模糊加速度以及信噪比改善因子,分析结果表明该方法较二次混频-DPT处理具有更低的信噪比门限。仿真结果验证了方法的有效性。

To solve the parameter estimation problem of accelerating target in LFMCW （linear frequency-modulated continuous wave） radar while MTRC （migration through range cell） occurs, a direct phase difference method is proposed. By direct phase differ- ence processing along the slow time dimension, the linear coupling of fast time and slow time is successfully removed, as well as the phase order reduction of the slow time dimension. Two dimensional FFT （fast Fourier transform） processing is carried out to the differ- enced signal, and acceleration estimation can be achieved, along with the coarse estimation of the initial velocity. Then the up-sweep and down-sweep beat signals are multiplied by the compensation .functions which are constructed based on the estimated parameters, re- spectively, and initial range and velocity can be accurately obtained through decoupling operation. Detail performances are analyzed, in- cluding the acceleration resolution, the maximum unambiguous acceleration and the SNR （signal-to-noise ratio） improvement factor. It shows that the proposed method has lower SNR threshold than secondary mixing combined DPT （ discrete polynomial-phase transform） processing. Simulation results testify the efficiency of the method.