Multi-Scale Time-Frequency Representation Fusion Network for Target Recognition in SAR Imagery

This paper proposes a multi-scale time-frequency representation fusion network (MTRFN) for target recognition in synthetic aperture radar (SAR) imagery. Leveraging the spectral characteristics of six radar sub-views, the model incorporates a multi-scale representation fusion (MRF) module to extract discriminative frequency-domain features from two types of radar sub-views with high learnability. Additionally, physical scattering characteristics in SAR images are captured via time-frequency domain analysis. To enhance feature integration, a gated fusion network performs adaptive feature concatenation. The MRF module integrates a lightweight residual block to reduce network complexity and employs a coordinate attention mechanism to prioritize salient targets in the frequency spectrum over background noise, aligning the model’s focus with physical scattering principles. Furthermore, the model introduces an angular additive margin loss function during classification to enhance intra-class compactness and inter-class separability while reducing computational overhead. Compared with existing interpretable methods, the proposed approach combines architectural transparency with physical interpretability, thereby lowering the risk of recognition errors. Extensive experiments conducted on four public datasets demonstrate that the proposed MTRFN significantly outperforms existing benchmark methods. Comparative experiments using heat maps further confirm that the proposed physical feature-guided module effectively directs the model’s attention toward the target rather than the background.