基于调频连续波雷达多域特征融合的低空目标识别方法

Multidomain Feature Fusion-Based Low-Altitude Target Recognition Method Using FMCW Radar

  • 摘要: 针对调频连续波(Frequency-Modulated Continuous-Wave,FMCW)雷达低空目标监测中悬停无人机与飞鸟回波特征相近、易产生误报漏报的问题,本文基于部分LSS-FMCWR-1.0多波段数据集和实测雷达回波数据开展微多普勒识别研究,提出融合“时频表征+物理先验”的双通路多域特征融合网络(Hybrid Physical-prior Multi-domain Network,HPMNet)。方法上,先对回波进行常规解调与杂波抑制,定位目标距离单元并得到微多普勒时频表示;同时从时频复矩阵中提取并构建统计特征,用于补充可解释的动力学信息。模型设计方面,时频分支采用局部—全局并行结构(Local-Global Time Frequency,LGTF),局部多尺度卷积采用多路并行设计并引入通道注意力以强化关键纹理;全局模块采用瓶颈式结构,在低分辨率空间内引入窗口自注意力(Window-based Self-Attention,WSA)捕获周期性与长程依赖,降低计算开销同时扩大感受野,之后上采样恢复分辨率;统计特征分支以深度交叉网络显式建模高阶交互,输出物理嵌入。两路特征通过门控加性融合模块自适应加权,可随信噪比与纹理退化动态自适应调整两路特征贡献,提升跨场景与跨波段泛化能力。实验结果表明,本文所提方法准确率达98.8%,相较单分支基线提升2.4%,与ResNet50等经典分类方法相比,提升准确率的同时,降低了运算量和参数量。消融与对比结果表明,物理统计特征提取分支与门控融合能缓解仅依赖时频纹理导致的过拟合,在低信噪比条件下仍保持较好鲁棒性,并提升整体可解释性,该方法为低空目标精细识别与监管应用提供重要支撑。

     

    Abstract: When monitoring low-altitude targets using frequency-modulated continuous-wave (FMCW) radar, hovering unmanned aerial vehicles and birds typically result in echoes with highly similar micro-Doppler signatures. This ambiguity often results in false alarms and missed detections, particularly in cluttered scenes and under low signal-to-noise ratio (SNR) conditions wherein time-frequency textures are weakened. Existing approaches that primarily rely on single-modality spectrogram textures may cause overfitting to specific acquisition settings and degrade when the texture becomes noisy or partially missing. Hence, we investigate micro-Doppler recognition based on a subset of the multiband LSS-FMCWR-1.0 dataset along with the measured FMCW radar echo data, and propose a two-path multidomain feature fusion network called HPMNet, which integrates time-frequency representation and physical priors in an end-to-end manner. The processing pipeline begins with conventional FMCW demodulation and clutter suppression. A target range cell is localized to extract the slow-time signal corresponding to the dominant target response, and a micro-Doppler time-frequency representation is generated as the primary learning input. Additionally, we exploit the complex-valued time-frequency matrix to compute a set of statistical descriptors and then assemble them into a structured feature vector. We design statistics to summarize the distribution, concentration, and variability of time-frequency energy as well as other stable characteristics that are closely related to the target micro-motion dynamics. Consequently, they provide physics-inspired priors that complement the spectrogram textures and offer an interpretable pathway that can remain informative even when the visual texture is degraded. In the network design, we adopt a local-global parallel architecture (LGTF) for the time-frequency branch. The local stream employs multiscale convolutions realized through multiple parallel routes to capture fine-grained textures, transient micro-motion structures, and subtle spectral modulations, and introduces squeeze-and-excitation channel attention to strengthen informative channels while suppressing background components. The global stream follows a bottleneck strategy: First, window-based self-attention is performed in a reduced-resolution feature space to capture periodicity and long-range dependencies with a lower computational cost while enlarging the effective receptive field. Next, the features are upsampled to restore the spatial resolution for subsequent fusion. This local-global design enables the branch to jointly model short-term details and longer-term temporal regularities in micro-Doppler patterns. The physics-prior branch is implemented using a deep and cross network to explicitly model high-order feature interactions among the statistical descriptors, resulting in a compact physical embedding. The two branches are integrated using a gated additive fusion module that adaptively reweights their contributions. By responding to SNR variations and time-frequency texture degradation, the gating mechanism can dynamically shift the reliance between spectrogram textures and physics-inspired statistical cues. This adaptive weighting improves robustness and enhances generalization across scenarios and frequency bands, as the model can emphasize the modality that is more reliable under the current conditions. Experimental results demonstrate that the proposed method achieves an accuracy of 98.8%, a 2.4% improvement over the single-branch baseline. Compared with classical classification methods such as ResNet50, the proposed method not only improves the classification accuracy but also reduces the computational cost and number of parameters. Ablation studies and comparative evaluations further confirm that the physical-statistical branch and gated fusion alleviate the overfitting caused by exclusive dependence on time-frequency textures, maintain favorable robustness under low-SNR conditions, and enhance interpretability by relating model outputs to measurable signal statistics. Therefore, the proposed method provides effective technical support for fine-grained recognition and regulatory applications of low-altitude targets.

     

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