Some new problems in distributed inverse synthetic aperture radar (ISAR) fusion imaging may be caused by constant frequency errors (CFE) due to the imperfect match of two independent oscillators. In this study, the effects of the CFE on distributed ISAR coherent fusion imaging are first analysed, which show that the CFE will produce false images (incorrect scatterer number and position) in distributed ISAR fusion imaging. To eliminate the effects of the CFE, a novel CFE calibration scheme is devised by exploiting the echo signal phase relationship between different sensors and making some reasonable approximations. The echo signal of the active radar (transmit and receive) is used as a reference signal. After some derivation, the phase relationship between the reference signal and other signals with CFE can be derived. Based on the derived phase relationship, the CFE of each radar will be estimated by multiple signal classification algorithm. Then, the estimated CFE value is further used to calibrate the CFE of each radar before signal coherent fusion. As a result, the false image is eliminated. Simulation results prove the authors theoretical analysis and the effectiveness of their method.

中文翻译：

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分布式ISAR融合成像中的恒定频率误差效应及其消除

由于两个独立振荡器的不完全匹配，恒定频率误差（CFE）可能引起分布式逆合成孔径雷达（ISAR）融合成像中的一些新问题。在这项研究中，首先分析了CFE对分布式ISAR相干融合成像的影响，这表明CFE在分布式ISAR融合成像中会产生错误的图像（散射体数量和位置不正确）。为了消除CFE的影响，通过利用不同传感器之间的回波信号相位关系并做出一些合理的近似，设计了一种新颖的CFE校准方案。有源雷达的回波信号（发送和接收）用作参考信号。经过一些推导，可以得出参考信号与其他具有CFE的信号之间的相位关系。基于导出的相位关系，将通过多信号分类算法估算每个雷达的CFE。然后，在信号相干融合之前，将估计的CFE值进一步用于校准每个雷达的CFE。结果，消除了虚假图像。仿真结果证明了作者的理论分析及其方法的有效性。