This paper is devoted to the estimation of target motion parameters with a forward scatter radar (FSR). To provide an upper bound for the estimation performance, a closed-form expression of the Cramér–Rao lower bound (CRLB) is provided for the main target signal parameters, namely Doppler rate, baseline crossing instant, and main lobe width parameter of the target amplitude modulation pattern. This is performed by operating on the signal at the output of the standard FSR processing scheme, namely on the crystal video detector signal: the received signal, which is passed through a square-law envelope detector followed by a DC removal filter. The estimate of the kinematic parameters of moving targets that follow a linear trajectory can be obtained by inverting the relationship between these parameters and the previously estimated target signal parameters. Especially, two FSR configurations are investigated: single-node FSR configuration and dual-baseline FSR configuration with a small angular separation between the two baselines. The closed-form expression of the corresponding CRLB is derived by using a linearized version of the same inverse transformation. Finally, a practical estimator is presented, based on a two-dimensional filter bank, and its performance is compared with the derived CRLB. The results show that unbiased and highly accurate estimates of the kinematic parameters are obtained. The feasibility and the effectiveness of this estimation scheme is demonstrated by applying this technique to recorded live data acquired with a dual-baseline FSR configuration exploiting FM signals as a waveform of opportunity.

中文翻译：

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前向散射雷达中的目标运动参数估计

本文致力于用前向散射雷达（FSR）估计目标运动参数。为了提供估计性能的上限，为主要目标信号参数，即目标的多普勒率、基线穿越时刻和主瓣宽度参数提供了克拉梅-拉奥下界 (CRLB) 的闭式表达式幅度调制模式。这是通过对标准 FSR 处理方案输出端的信号进行操作来执行的，即对晶体视频检测器信号进行操作：接收的信号通过平方律包络检测器，然后通过直流去除滤波器。通过对这些参数与先前估计的目标信号参数之间的关系进行反演，可以获得对遵循线性轨迹的运动目标的运动学参数的估计。特别是，研究了两种 FSR 配置：单节点 FSR 配置和双基线 FSR 配置，两个基线之间的角度间隔很小。对应 CRLB 的闭式表达式是通过使用相同逆变换的线性化版本导出的。最后，提出了一种基于二维滤波器组的实用估计器，并将其性能与导出的 CRLB 进行了比较。结果表明，获得了对运动学参数的无偏和高度准确的估计。