HET: An Efficient High-Frequency Enhancement Transformer for Specific Emitter Identification

Specific emitter identification (SEI) is a crucial task in various applications such as wireless communications and radar systems. The low-pass nature of vanilla Transformers hinders the extraction of high-frequency fingerprint features, resulting in poor SEI performance. Moreover, the introduction of additional high-frequency sensing structures can increase the computational efficiency of the already computationally intensive Transformer. To address these issues, we propose a high-frequency enhanced and low-complexity Transformer named HET. The framework integrates a multihead low-complexity self-attention (MLSA) module, a high-frequency enhanced connection, and a multihead high-frequency enhanced low-complexity self-attention (MESA) module. The MLSA module reduces the computational complexity by key and value mapping. The MESA and high-frequency enhanced connection module capture high-frequency information by reconstructing the low-frequency and high-frequency components of the features. We construct three HET variants, namely, $\text {HET}_{n}$ , $\text {HET}_{u}$ , and $\text {HET}_{m}$ , based on different enhancement methods and positions using $\text {MESA}_{n}$ , $\text {MESA}_{u}$ , and $\text {MESA}_{m}$ , respectively. Extensive experiments are conducted on the XSRP, ADS-B, and Wi-Fi datasets to evaluate the proposed models, demonstrating their competitive accuracy and faster throughput compared with popular methods. Theoretical proofs of high-frequency suppression and frequency response results confirm that the proposed framework has more gain for high-frequency information in SEI. Code is available at: https://github.com/zhailei-zl/HETmodel.