Online Decision-making Method for Frequency-agile Radar Based on Multi-Armed Bandit
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摘要: 频率捷变技术发挥了雷达在电子对抗中主动对抗优势,可以有效提升雷达的抗噪声压制式干扰性能。然而,随着干扰环境的日益复杂,在无法事先了解环境性质的情况下,设计一种具有动态适应能力的频率捷变雷达在线决策方法是一个具有挑战性的问题。该文根据干扰策略的特征,将压制式干扰场景分为3类,并以最大化检测概率为目标,设计了一种基于多臂赌博机(MAB)的频率捷变雷达在线决策方法。该方法是一种在线学习算法,无需干扰环境的先验知识和离线训练过程,在不同干扰场景下均实现了优异的学习性能。理论分析和仿真结果表明,与经典算法和随机捷变策略相比,所提方法具有更强的灵活性,在多种干扰场景下均能够有效提升频率捷变雷达的抗干扰和目标检测性能。
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关键词:
- 频率捷变 /
- 噪声压制式干扰 /
- 检测概率 /
- 多臂赌博机(MAB) /
- 在线学习
Abstract: Frequency agile technology provides full play to the advantage of radars for adopting electronic countermeasures actively, which can effectively enhance the antinoise suppression jamming performance of radars. However, with the increasing complexity of the interference environment, developing an online decision-making method for frequency-agile radar with dynamic adaptability and without foresight of the nature of the environment is a demanding task. According to the features of the jamming strategy, suppression jamming scenarios are divided into three categories, and an online decision-making method for frequency-agile radar based on Multi-Armed Bandit (MAB) is developed to maximize the radar’s detection probability. This approach is an online learning algorithm that does not need to interfere with the foresight of the environment and offline training process and realizes remarkable learning performance from noninterference scenarios to adaptive interference scenarios. The simulation results and theoretical analysis demonstrate that compared with the classical algorithm and stochastic agile strategy, the proposed method has stronger flexibility and can effectively improve the antijamming and target detection performances of the frequency-agile radar for various jamming scenarios. -
1 RAFA-EXP3++算法
1. RAFA-EXP3++ algorithm
初始化:频率通道数N, $\forall {f_i} \in \mathcal{F}$,初始损失估计值 ${\tilde L_0}({f_i}) = 0$,权重 ${w_0}({f_i}) = 1$,损失期望差估计值 $ {\hat \varDelta _0}({f_i}) $=1 对于每一个脉冲重复周期 $t = 1,2, \cdots ,T$ 1. 设置参数: ${\beta _{t}} = \dfrac{1}{2}\sqrt {\dfrac{{\ln N}}{{tN}}} $; ${\eta _{t}} = 2{\beta _{t}}$; $c = 20$; $\forall {f_i} \in \mathcal{F}$: $ {\xi _{t}}({f_i}) = \dfrac{{c{{(\ln t)}^2}}}{{t{{\hat \varDelta }_{t - 1}}{{({f_i})}^2}}} $; ${\varepsilon _{t}}({f_i}) = \min \left\{ \dfrac{1}{{2N}},{\beta _{t}},{\xi _{t}}({f_i})\right\} $ 2. $\forall {f_i} \in \mathcal{F}$,计算各频率通道选择概率 ${p_{t}}({f_i})$: ${p_{t}}({f_i}) = \left(1 - \displaystyle\sum\limits_{j = 1}^N {{\varepsilon _{t}}({f_j})} \right)\dfrac{{{w_{t - 1}}({f_i})}}{{\displaystyle\sum\limits_{j = 1}^N {{w_{t - 1}}({f_j})} }} + {\varepsilon _{t}}({f_i})$ (11) 3. 依概率 ${p_{t}}$从可用频率通道集 $\mathcal{F}$中选择发射频率通道 ${f_a}$,接收回波信号并利用式(5)计算损失值 ${l_{t}}({f_a})$。 4. $\forall {f_i} \in \mathcal{F}$,更新各频率通道权重值 $ {w_{t}}({f_i}) $和损失期望差估计值 $ {\hat \varDelta _{t}}({f_i}) $: $ {\tilde{L}}_{t}({f}_{i})=\left\{\begin{array}{cc}{\tilde{L}}_{t-1}({f}_{i})+\dfrac{{l}_{t}({f}_{i})}{{p}_{t}({f}_{i})},& 当{f}_{i}={f}_{a}时\\ {\tilde{L}}_{t-1}({f}_{i}),& 当{f}_{i}\ne {f}_{a}时\end{array} \right. $ (12) $ {w_{t}}({f_i}) = \exp \left( - {\eta _{t}}{\tilde L_{t}}({f_i})\right) $ (13) $ {\hat \varDelta _{t}}({f_i}) = \min \left\{ {1,\dfrac{1}{t}\left( {{{\tilde L}_{t}}({f_i}) - \mathop {\min }\limits_{{f_j} \in \mathcal{F}} {{\tilde L}_{t}}({f_j})} \right)} \right\} $ (14) 表 1 仿真实验雷达参数
Table 1. Radar parameters of simulation experiment
参数 数值 工作频段 Ku频段 信号带宽B 40 MHz 频率通道数N 30 脉冲重复周期 ${T_{\mathrm{r}}}$ 20 μs 发射功率 ${P_{t}}$ 1000 W 发射天线增益G 40 dB 雷达系统损耗 ${L_{s}}$ 4 dB 接收机带宽 ${B_{\rm n}}$ 40 MHz 接收机噪声系数 ${F_{\rm n}}$ 3 dB 虚警率 ${P_{{\mathrm{fa}}}}$ ${10^{ - 4}}$ 目标的径向距离R 10 km 表 2 仿真实验中目标RCS均值(m2)
Table 2. The mean RCS of target in the simulation experiment (m2)
频率通道 RCS均值 1~5 $U(8.5,9.5)$ 6 $14$ 7~15 $U(8.5,10.0)$ 16~30 $U(9.0,9.5)$ 表 3 仿真实验干扰机部分参数
Table 3. Jammer parameters of simulation experiment
参数 数值 干扰机发射总功率 ${P_{\mathrm{J}}}$ 800 W 干扰机天线增益 ${G_{\mathrm{J}}}$ 10 dB 雷达在干扰方向增益 $G(\theta )$ 20 dB 极化失配损失 ${\gamma _{\mathrm{J}}}$ 0.5 干扰系统损耗 ${L_{\mathrm{J}}}$ 5 dB 与雷达的径向距离 ${R_{\mathrm{J}}}$ 15 km 表 4 扫频式干扰参数设置
Table 4. Parameter setting of sweeping frequency jamming
参数 数值 扫频带宽 1.2 GHz 干扰带宽 200 MHz 跳频带宽 200 MHz 扫频周期 120 μs 表 5 非自适应干扰场景中检测到目标的次数
Table 5. The number of detected targets in non-adaptive jamming scene
算法名称 次数 Random 53965 $\varepsilon {\text{-}} {\mathrm{Greedy}}$ 66838 UCB1 55951 EXP3 72825 CDTS 55345 RAFA-EXP3++ 72837 表 6 自适应干扰场景下检测到目标的次数
Table 6. The number of detected targets in adaptive jamming scene
算法名称 次数 Random 54048 $\varepsilon {\text{-}} {\mathrm{Greedy}}$ 27423 UCB 1 16265 EXP3 55135 CDTS 33723 RAFA-EXP3++ 55170 -
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