异步采集条件下的通信辐射源个体识别
Communication Emitter Identification Under Asynchronous Acquisition Condition
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摘要: 针对非合作条件下数据异步采集造成的个体识别结果漂移问题,提出一种异步采集条件下的通信辐射源个体识别方法。首先,建立信号异步采集的测量模型,分析了多径信道干扰、目标相对运动、接收机个体差异等时频异步场景对测量信号的影响,分析推导出时延和频移是造成个体识别特征发散的主要因素;其次,为了降低时延和频移对信号细微特征的干扰,利用短时傅里叶变换(Short-Time Fourier Transform, STFT)将时延和频移转化为信号特征在时频平面上的坐标位置,并通过统一的时频分辨尺度提高信号特征的稳定性,推导分析了时频域特征测量误差,指出时延和频移会造成时频特征的位置抖动,间接影响特征测量精度;再次,为了降低时频特征位置抖动影响,提出利用精细化时频测量技术提取信号细微特征,给出了基于频域移频补全消除时频栅栏效应的算法;最后,利用信号的精细化时频特征图,将辐射源个体识别转化为基于深度学习细粒度图像识别问题,采用DenseNet201迁移学习网络和图像增强技术验证了算法的有效性。外场实验结果表明:针对同类型船舶自动识别系统(Automatic Identification System, AIS),在不同采集设备、采样参数和采样时空的异步采集条件下,对10个通信辐射源的Top-1个体识别准确率达到了85%以上。Abstract: An asynchronous data acquisition method for communication emitter identification under non-cooperative conditions is proposed to alleviate the problem of recognition drift. Firstly, a measurement signal model is established under asynchronous acquisitions. The impact of time-frequency asynchronous scenarios, including multipath channel interference, relative motion of the target, and receiver-specific differences, on the measurement signal is analyzed in detail. Time delay and frequency shift are demonstrated to be the primary factors contributing to the divergence of identification features. Secondly, to mitigate the interference of time delays and frequency shifts on the subtle characteristics of the signal, these effects are transformed into coordinate positions of signal features on time-frequency domain (TFD) using short-time Fourier transform (STFT). A unified time-frequency resolution scale is applied to enhance the stability of signal features. Measurement errors in TFD are derived and analyzed, which highlight that time delay and frequency shift induce position jitter in time-frequency features (TFFs), and thus, indirectly affect feature measurement accuracy. Thirdly, to reduce the influence of TFFs position jitter, refined time-frequency measurement technology is employed to extract fine-grained signal features. An algorithm to eliminate the time-frequency fence effect based on frequency-domain frequency shift compensation is presented. Finally, leveraging the refined TFFs of the signal, emitter individual identification is reformulated as a fine-grained image recognition problem based on deep learning. The effectiveness of the proposed algorithm is validated using the DenseNet201 transfer learning network and image enhancement technique. Field experiments demonstrate that for shipborne automatic identification systems (AIS) of the same type, under asynchronous acquisition conditions with varying sampling devices, parameters, time and space, the Top-1 individual identification accuracy rate for 10 communication emitters exceeds 85%.
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