A Neural Network-Based Robust Direction Finding Algorithm for Mixed Circular and Non-Circular Signals Under Array Imperfections
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摘要: 针对阵列误差影响下圆和非圆信号混合入射的波达方向(DOA)估计问题,该文提出一种基于改进视觉转换器(ViT)模型的鲁棒测向算法。该算法通过构建六通道类图像输入架构,融合接收信号的协方差矩阵实部、虚部、相位、幅值及非圆扩展特性,利用梯度掩码机制实现核心特征与辅助特征的自适应融合,充分提取并挖掘了非圆信号伪协方差矩阵中蕴含的额外信息;同时改进传统ViT模型结构,增加特征融合及卷积模块,并设计前后双分类标记注意力机制,增强模型对信号的学习能力和适应性。实验结果表明,该算法在低信噪比、圆与非圆信号混合及多种阵列误差共存等复杂场景下,相比于现有方法展现出了更好的鲁棒性和测向精度。此外,该算法对快拍数变化及未知调制类型的信号亦表现出良好的适应性与稳定性,为复杂环境中的波达方向估计提供了一种新的有效方法。
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关键词:
- 波达方向估计 /
- 多类型圆与非圆混合信号 /
- 多种阵列误差 /
- 多特征融合 /
- Vision Transformer模型
Abstract:Objective Direction Of Arrival (DOA) estimation is affected by low Signal-to-Noise Ratios (SNR), the coexistence of Circular Signals (CSs) and Non-Circular Signals (NCSs), and multiple forms of array imperfections. Conventional subspace-based estimators exhibit model mismatch in such environments and show reduced accuracy. Although neural-network methods provide data-driven alternatives, the effective use of the distinctive statistical properties of NCSs and the maintenance of robustness against diverse array errors remain insufficiently addressed. The objective is to design a DOA estimation algorithm that operates reliably for mixed CSs and NCSs in the presence of array imperfections and provides improved estimation accuracy in challenging operating conditions. Methods A robust DOA estimation algorithm is proposed based on an improved Vision Transformer (ViT) model. A six-channel image-like input is first constructed by fusing features derived from the covariance matrix and pseudo-covariance matrix of the received signal. These channels include the real component, imaginary component, magnitude, phase, magnitude ratio reflecting the NCS characteristic, and the phase of the pseudo-covariance matrix. A gradient-masking mechanism is introduced to adaptively fuse core and auxiliary features. The ViT architecture is then modified: the standard patch-embedding module is replaced with a convolutional layer to extract local information, and a dual-class-token attention mechanism, placed at the sequence head and tail, is designed to enhance feature representation. A standard Transformer encoder is used for deep feature learning, and DOA estimation is performed through a multi-label classification head. Results and Discussions Extensive simulations are carried out to assess the proposed algorithm (6C-ViT) against MUSIC, NC-MUSIC, a Convolutional Neural Network (6C-CNN), a Residual Network (6C-ResNet), and a Multilayer Perceptron (6C-MLP). Performance is evaluated using Root Mean Square Error (RMSE) and angular estimation error under different operating conditions. Under single-source scenarios with low SNR and no array errors, 6C-ViT achieves near-zero RMSE across most angles and shows minor edge deviations ( Fig. 2 ). It maintains the lowest RMSE across the SNR range from –20 dB to 15 dB (Fig. 3 ), indicating good generalization to unseen SNR levels. In dual-source scenarios containing mixed CS and NCSs under array errors, 6C-ViT shows clear advantages. Its estimation errors fluctuate slightly around zero, whereas competing techniques present larger errors and pronounced instabilities, especially near array edges (Fig. 4 ). Its RMSE decreases steadily as SNR increases and reaches below 0.1° at high SNR, while traditional approaches saturate around 0.4° (Fig. 5 ). Robust behavior is further observed across different numbers of signal sources (K = 1, 2, 3) and snapshot counts (100 to 2 000). 6C-ViT preserves high accuracy and stability under these variations, whereas other methods show marked degradation or instability, most evident at low snapshot counts or with multiple sources (Fig. 6 ). When evaluated using unknown modulation types, including UQPSK with a non-circularity rate of 0.6 and 64QAM, under array errors, 6C-ViT continues to produce the lowest RMSE across most angles (Fig. 7 ), demonstrating strong generalization capability. Ablation studies (Fig. 8 ) confirm the contributions of the six-channel input, the gradient masking module, the convolutional embedding, and the dual class token mechanism. The complete configuration yields the highest accuracy and the most stable performance.Conclusions Strong robustness is demonstrated in complex scenarios that contain mixed CS and NCSs, multiple array imperfections, low SNR, and closely spaced sources. By fusing multi-dimensional features of the received signal and using an enhanced Transformer architecture, the algorithm attains higher estimation accuracy and improved generalization across different signal types, error conditions, snapshot counts, and noise levels compared with subspace- and neural-network-based baselines. The method provides a reliable DOA estimation solution for demanding practical environments. -
表 1 模型超参数选择
参数名称 参数选取 参数名称 参数选取 图像大小 16×16 学习率衰减因子 0.05 卷积核大小 2×2 权重衰减 0.05 卷积核数量 243 Dropout率 0.2 Transformer层数 6 Attention Dropout率 0.2 注意力头数 9 Drop Path率 0.2 MLP扩展比率 4.0 优化器类型 AdamW 训练轮数 120 Adam Beta1 0.9 批量大小 90 Adam Beta2 0.999 初始学习率 3e-4 分类类别数 121 表 2 算法复杂度对比表
FLOPs Params 6C-CNN 9.649 87×107 2.819 75×107 6C-MLP 2.001 98×106 1.001 28×106 6C-ResNet 3.656 42×107 1.820 41×106 6C-ViT 4.822 30×108 4.351 52×106 表 3 消融实验对比模型配置表
对比模型编号 配置 Model-A 标准ViT+3通道输入(实部、虚部、相位) Model-B 标准ViT+6通道输入 Model-C 标准ViT+6通道输入+梯度掩码 Model-D 传统ViT+3通道输入+卷积(CNN)嵌入层 Model-E 传统ViT +3通道输入+前后双分类标记 本文 传统ViT +6通道输入+梯度掩码+ CNN嵌入层+
前后双分类标记 -
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