Distorted Radar Electromagnetic Signal Recognition Based on Meta-learning
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摘要: 畸变雷达电磁信号会严重影响雷达侦察装备的探测性能。如何有效地识别畸变信号类型对侦察系统的精确感知具有重要现实意义。针对畸变雷达信号往往存在样本稀缺的问题,该文提出一种基于模型无关元学习的残差网络(MAML-ResNet)。算法首先利用正常雷达信号样本训练元学习器,然后在畸变信号样本进行精调,最后在仅有少量畸变信号样本下,实现畸变信号的识别。实验结果表明该算法有效地提高了在小样本数据下畸变信号的识别准确率。Abstract: Distorted radar electromagnetic signals will seriously affect the detection performance of radar reconnaissance equipment. How to identify effectively the type of distorted signal has important practical significance for the accurate perception of radar systems. For distorted radar signals, there is often a problem of sample scarcity. A Residual Network based on Model-Agnostic Meta-Learning (MAML-ResNet) is proposed. The algorithm first uses normal radar signal samples to train the meta-learner, then the meta-learner is fine-tuned in the distorted signal samples. Finally, the distorted signal is recognized with only a small number of distorted signal samples. Experimental results show that the recognition accuracy of distorted signals under small sample data is effectively improved.
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Key words:
- Distorted radar signal recognition /
- Deep learning /
- Few-shot learning /
- Meta learning
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表 1 算法MAML流程
输入:创建若干个任务$ p(\mathcal{T}) $,步长超参数$ \alpha $,$ \beta $ 输出:模型参数${\boldsymbol{\theta}}$ (1) 随机初始化${\boldsymbol{ \theta}}$ (2) 循环1: (3) 随机对若干个任务采样$ {\mathcal{T}_i} \sim p(\mathcal{T}) $ (4) 循环2(对所有的任务$ {\mathcal{T}_i} $): (5) 根据$ K $个样本计算梯度${\nabla _{\boldsymbol{\theta}} }{\mathcal{L}_{ {\mathcal{T}_i} } }\left( { {f_{\boldsymbol{\theta}} } } \right)$ (6) 利用梯度下降法更新参数:${ {\boldsymbol{\theta} } '_i}{\text{ = } }{\boldsymbol{\theta}} - \alpha {\nabla _{\boldsymbol{\theta}} }{\mathcal{L}_{ {\mathcal{T}_i} } }\left( { {f_{\boldsymbol{\theta}} } } \right)$ (7) 循环2结束 (8) 更新参数$\theta \leftarrow {\boldsymbol{\theta} } - \beta {\nabla _{\boldsymbol{\theta} } }\sum {_{ {\mathcal{T}_i} \sim p(\mathcal{T})} } {\mathcal{L}_{ {\mathcal{T}_i} } }\left( { {f_{ { { {\boldsymbol{\theta } }'}_i} } } } \right)$ (9) 循环1结束 表 2 ResNet结构参数
层数 输出尺寸/像素 对应卷积层 Conv1 $ {\text{112}} \times {\text{112}} $ Conv2_x $ {\text{56}} \times {\text{56}} $ $ \left[\begin{array}{cc}\text{3}\times \text{3},& \text{64}\\ \text{3}\times \text{3},& \text{64}\end{array}\right]\times \text{2} $ Conv3_x $ {\text{28}} \times {\text{28}} $ $ \left[\begin{array}{cc}\text{3}\times \text{3},& \text{128}\\ \text{3}\times \text{3},& \text{128}\end{array}\right]\times \text{2} $ Conv4_x $ {\text{14}} \times {\text{14}} $ $ \left[\begin{array}{cc}\text{3}\times \text{3},& \text{256}\\ \text{3}\times \text{3},& \text{256}\end{array}\right]\times \text{2} $ Conv5_x $ {\text{7}} \times {\text{7}} $ $ \left[\begin{array}{cc}\text{3}\times \text{3},& \text{512}\\ \text{3}\times \text{3},& \text{512}\end{array}\right]\times \text{2} $ 全连接层 $ {\text{1}} \times {\text{1}} $ 表 3 人工特征提取方法特征集合
表 4 畸变雷达信号识别结果(%)
方法 信噪比0~6 dB 信噪比7~13 dB 信噪比14~20 dB 5 way 5 shot 5 way 10 shot 5 way 5 shot 5 way 10 shot 5 way 5 shot 5 way 10 shot Decision Tree 60.9±1.5 70.1±0.2 68.0±0.3 78.6±0.3 69.3±0.7 79.5±0.2 K-NN 63.2±0.3 74.6±0.2 77.8±0.2 84.2±0.2 79.0±0.2 85.3±0.1 SVM 58.1±0.7 73.3±0.2 73.6±0.4 85.0±0.1 73.8±0.7 86.8±0.1 ResNet 38.8±1.5 51.1±1.9 59.8±0.4 67.8±0.3 52.3±0.5 56.6±0.3 MAML-ResNet 76.8±0.2 82.3±0.1 86.6±0.1 87.1±0.1 89.9±0.1 94.3±0.1 表 5 高信噪比元学习器下畸变雷达信号识别结果(%)
方法 信噪比0~6 dB 信噪比7~13 dB 5 way 5 shot 5 way 10 shot 5 way 5 shot 5 way 10 shot MAML-ResNet 72.7±0.2 78.9±0.1 83.7±0.1 86.3±0.1 表 6 低信噪比元学习器下畸变雷达信号识别结果(%)
方法 信噪比7~13 dB 信噪比14~20 dB 5 way 5 shot 5 way 10 shot 5 way 5 shot 5 way 10 shot MAML-ResNet 84.6±0.1 88.3±0.1 90.9±0.1 94.4±0.1 -
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