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摘要: 非合作双基地雷达凭借其抗隐身、抗干扰等特性,在民用与军用领域具有重要应用价值。然而在实际应用中,不可控雷达辐射源及复杂地理环境导致参考信号中不可避免地混入多径干扰与噪声污染,致使参考信号与回波信号互相关处理检测性能显著劣化于理想最优匹配滤波器,并产生固定虚假目标,成为制约非合作双基地雷达实战应用的瓶颈问题。该文针对该问题展开系统性研究:首先分析了参考通道存在多径和噪声时的互相关结果,定量分析了参考通道中多径强度和噪声功率与检测概率的映射关系。其次针对线性调频信号,提出了一种基于去斜解调的参考通道多径抑制算法,该算法利用线性调频信号特性,将不同时延的多径分量转化为显著的频率偏移,相同多径分量相较于现有主流分数阶傅里叶变化产生更大频移效果,能以显著降低滤波器阶数实现相当的抑制效果,得益于更彻底的信号分离度,相较于常规算法该算法在整体上能更有效地提升目标检测概率。在强多径淹没直达波的实际外场试验场景下,实测数据处理结果验证了所提方法在消除虚假目标、修正距离偏移和提升目标检测概率方面的有效性。Abstract: Non-cooperative bistatic radar exhibits significant application value for both civilian and military applications due to its anti-stealth and anti-jamming capabilities. However, its practical implementation faces challenges from unavoidable multipath interference and noise contamination in reference signals, stemming from uncontrollable radar illuminators and complex geographical environments. These effects substantially degrade the performance of cross-correlation processing between reference and echo signals compared with the ideal matched filter, resulting in stationary false targets. Such issues remain a critical bottleneck to operational deployment. This study systematically addresses these challenges by analyzing cross-correlation degradation under multipath and noise in the reference channel, and by establishing a quantitative mapping between multipath intensity, noise power, and detection probability. For Linear Frequency Modulated (LFM) signals, a dechirp-based multipath suppression algorithm is proposed. The algorithm exploits the inherent properties of LFM signals, transforming multipath components with different delays into distinct frequency offsets. Compared with mainstream Fractional Fourier Transform methods, this approach exhibits greater frequency separation among multipath components, enabling effective suppression with significantly reduced filter orders. The algorithm outperforms conventional methods in improving overall detection probability. Measured data processing in practical field-test scenarios (direct-path signals overwhelmed by strong multipath interference) validates the method’s efficacy in eliminating false targets, correcting range offsets, and enhancing detection probability.
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表 1 目标检测性能仿真参数
Table 1. Target detection performance simulation parameters
参数 数值 参数 数值 脉宽 100 μs 带宽 5 MHz 重复周期 1 ms 采样频率 20 MHz 参考通道直达波功率 40 dBm, 25 dBm 监视通道直达波功率 20 dBm 参考通道多径时延范围 (0.2 μs, 1.5 μs] 监视通道杂波总功率($ \sum\nolimits_{i = 0}^L {\beta _i^2} $) 10 dBm 参考通道多径数量 10 监视通道目标回波功率 –20 dBm 参考通道中信干比 [0 dB, 40 dB] 监视通道目双基地时延 140 μs 表 2 仿真参数
Table 2. Simulation parameters
参数 数值 参数 数值 脉冲宽度 30 μs 目标回波信噪比 –15 dB, –5 dB 重复周期 100 μs 目标双基地延时 40 μs, 45 μs 调频带宽 5 MHz 多径延时范围 (0 μs, 10 μs] 参考通道直达波信噪比 40 dB 参考通道多径数量 10 载频 0 MHz 参考通道信号信干比 10 dB CFAR训练单元 60 监视通道直达波信噪比 20 dB CFAR保护单元 8 采样频率 20 MHz 滤波器阶数 71 CFAR虚警概率 $1 \times {10^{ - 6}}$ -
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