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,提出了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 faces significant challenges in practical environments characterized by low signal-to-noise ratios (SNR), the coexistence of circular and non-circular signals, and various array imperfections. Traditional subspace algorithms often suffer from model mismatch and performance degradation under these complex conditions. While deep learning offers promising data-driven solutions, effectively leveraging the unique statistical properties of non-circular signals and ensuring robustness against diverse array errors remain critical yet under-explored areas. This study aims to develop a robust DOA estimation algorithm capable of handling mixed signals and array imperfections, thereby enhancing estimation accuracy and reliability in challenging scenarios. Methods This paper proposes a robust DOA estimation algorithm based on an improved Vision Transformer (ViT) model. First, a novel six-channel, image-like input structure is constructed by fusing multiple features derived from the received signal's covariance matrix and pseudo-covariance matrix, including the real part, imaginary part, magnitude, phase, magnitude ratio (for non-circular characteristic), and phase of the pseudo-covariance matrix. A gradient masking mechanism is introduced to adaptively fuse these core and auxiliary features. Second, the traditional ViT architecture is enhanced: the standard patch embedding is replaced with a convolutional layer for better local feature extraction, and a dual-class token attention mechanism (one at the sequence head and one at the tail) is designed to enrich feature representation. The model utilizes a standard Transformer encoder for deep feature learning and ultimately performs DOA estimation via a multi-label classification head. Results and Discussions Extensive simulations were conducted to evaluate the proposed algorithm (6C-ViT) against several benchmarks, including MUSIC, NC-MUSIC, CNN-based (6C-CNN), ResNet-based (6C-ResNet), and MLP-based (6C-MLP) methods. Performance was assessed using Root Mean Square Error (RMSE) and angular estimation error under various conditions.Under single-source scenarios with low SNR and no array errors, the proposed 6C-ViT achieved near-zero RMSE across most angles, particularly in the central region, and demonstrated minimal edge errors ( Fig. 2 ). It maintained the lowest RMSE across the tested SNR range from –20 dB to 15 dB (Fig. 3 ), showing good generalization even to untrained SNR levels. In dual-source scenarios involving mixed circular and non-circular signals under array errors, 6C-ViT significantly outperformed all competitors, with estimation errors fluctuating minimally around zero, while other methods exhibited larger errors and instabilities, especially at array edges (Fig. 4 ). Its RMSE decreased consistently with increasing SNR, dropping below 0.1° at high SNR, whereas traditional methods plateaued around 0.4° (Fig. 5 ). Further tests confirmed 6C-ViT's strong adaptability and robustness. It exhibited superior performance and stability across varying numbers of signal sources (K=1,2,3) and snapshot numbers (from 100 to 2 000), where other methods showed significant performance degradation or instability, particularly at low snapshots or with multiple sources (Fig. 6 ). When tested with unknown modulation signals (UQPSK with non-circularity rate 0.6 and 64QAM) under array errors, 6C-ViT maintained the lowest RMSE across most angles (Fig. 7 ), demonstrating excellent generalization capability. Ablation studies (Fig. 8 ) verified the individual contributions of the proposed six-channel input, gradient masking, convolutional embedding, and dual-class token mechanism, with the complete model delivering the best overall performance.Conclusions The proposed improved ViT-based DOA estimation algorithm demonstrates superior performance and strong robustness in complex scenarios involving mixed circular and non-circular signals, multiple array imperfections, low SNR, and closely spaced sources. By effectively fusing multi-dimensional signal features and leveraging an enhanced Transformer architecture, the algorithm achieves higher estimation accuracy and better generalization across varying signal types, error conditions, snapshot numbers, and noise environments compared to existing subspace and deep learning methods. This work provides an effective solution for reliable DOA estimation in challenging practical settings. -
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 9.64987×107 2.81975×107 6C-MLP 2.00198×106 1.00128×106 6C-ResNet 3.65642×107 1.82041×106 6C-ViT 4.82230×108 4.35152×106 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+三通道输入(实部、虚部、相位) Model-B 标准ViT+六通道输入 Model-C 标准ViT+六通道输入+梯度掩码 Model-D 传统ViT+三通道输入+卷积(CNN)嵌入层 Model-E 传统ViT +三通道输入+前后双分类标记 Ours 传统ViT +六通道输入+梯度掩码+ CNN嵌入层+前后双分类标记 -
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