电控时变电磁材料的SAR成像特性研究

微动目标因具有在不同方向的运动分量，能够对电磁波进行微多普勒调制，导致目标成像特征出现方位向散焦效应，这种现象在目标识别与反识别领域被广泛关注与研究。相较而言，电控时变电磁材料通过外加激励实现对电磁波特征的灵活调控，具有更快的调制速度，而其成像特性没有被过多关注。该文以此为切入点，对电控时变电磁材料的合成孔径雷达(SAR)图像距离向调制特性进行了研究，分析了时变电磁材料谱变换模型和SAR目标特征控制原理。以相位调制表面(PSS)为代表，建立了非周期PSS相位调制模型，其频谱具有连续频移特性。在此基础上，探讨了PSS连续频移调制对SAR的影响，揭露了距离向目标散焦现象。通过SAR实测数据仿真，验证了所提理论方法的有效性。 

Synthetic Aperture Rader Imaging Characteristics of Electronically Controlled Time-varying Electromagnetic Materials

Micromotion targets can enable microDoppler modulation on electromagnetic waves owing to their motion components in different directions, resulting in the defocusing effects of the target imaging features along the azimuth direction. This phenomenon has been widely considered and investigated in target recognition and antirecognition. As a research hotspot, electronically controlled time-varying electromagnetic materials have fast modulation characteristics; however, their imaging characteristics have not received much attention. This study investigates the Synthetic Aperture Radar (SAR) modulation characteristics along the range direction of electronically controlled time-varying electromagnetic materials. Then, this study establishes the time-varying electromagnetic material spectrum transformation model and analyzes the SAR target characteristic control principle. Taking the Phase-Switched Screen (PSS) as an example, a nonperiodic PSS phase modulation model is established, and its spectrum has continuous frequency shift characteristics. On this basis, the influence of continuous frequency shift modulation induced by nonperiodic PSS on SAR was further discussed and the defocusing phenomenon of the target along the range direction was detected. Through the simulation of measured data, the validity of the proposed theoretical method is verified.