FUNDAMENTAL INVESTIGATION OF INVERSE SCATTERING PROBLEM BY MEANS OF MICROWAVE

1. 提出了一种用于合成孔径雷达的完全导电半球散射校准器。由于半径和半球配置的优化，表明这种新的校准器与传统的角反射器相比是非常有用的。本文提出了一种利用波和tm波或两者同时利用一组离散频率和/或入射角的噪声反射系数数据估计一维非均匀层状介质介电常数和电导率的方法。各种数值算例表明，该方法是非常有效的。研究还表明，利用实测反射系数数据的误差方差可以有效地提前估计重构剖面的误差方差。本文还研究了时域逆方法。提出了一种重构介电常数剖面的方法，并证明了该方法的有效性。我们计划详细探讨有耗介质的时域逆散射技术。研究了完美导电物体的雷达成像。提出了基于扩展物理光学近似法的迭代逆散射法重建目标轮廓。结果表明，该方法对轴对称散射体是非常有效的。我们正计划把这种方法推广到三维物体上。为了得到超长导体散射体的逆散射算法，对放置在无限导体圆柱体附近的偶极子天线的瞬态响应进行了严格的分析。

1. A SCATTERING CALIBRATOR COMPOSED OF PERFECTLY CONDUCTING HEMISPHERES FOR THE SYNTHETIC APERTURE RADAR HAS BEEN PROPOSED. AS A RESULT OF THE OPTIMIZATION OF THE RADII AND THE DISPOSITION OF THE HEMISPHERES, IT HAS BEEN CLARIFIED THAT THIS NEW CALIBRATOR IS VERY USEFUL COMPARED WITH THE CONVENTIONAL CORNER REFLECTOR.2. A METHOD TO ESTIMATE THE PERMITTIVITY AND THE CONDUCTIVITY OF ONE DIMENSIONAL INHOMOGENEOUS LAYERED MEDIUM FROM NOISY REFLECTION COEFFICIENT DATA FOR A SET OF DISCRETE FREQUENCIES AND/OR INCIDENT ANGLES WHICH MAKES USE OF TE WAVE AND TM WAVE OR BOTH, HAS BEEN PROPOSED. IT HAS BEEN DEMONSTRATED IN TERMS OF VARIOUS NUMERICAL EXAMPLES THAT THIS NEW METHOD IS VERY EFFECTIVE. IT HAS BEEN ALSO INDICATED THAT THE ERROR VARIANCE OF THE RECONSTRUCTED PROFILE CAN BE EFFECTIVELY ESTIMATED IN ADVANCE FROM THE ERROR VARIANCE OF THE MEASURED REFLECTION COEFFICIENT DATA. THE TIME DOMAIN INVERSE METHOD HAS ALSO INVESTIGATED. A METHOD TO RECONSTRUCT THE PERMITTIVITY PROFILE HAS BEEN PROPOSED, AND HAS INDICATED THAT THIS METHOD IS EFFECTIVE. WE ARE PLANNING TO EXPLORE THE TIME DOMAIN INVERSE SCATTERING TECHNIQUES FOR LOSSY MEDIUM IN DATAIL.3. THE RADAR IMAGING OF THE PERFECTLY CONDUCTING OBJECT HAS BEEN STUDIED. THE ITERATIVE INVERSE SCATTERING METHOD TO RECONSTRUCT THE PROFILE OF THE OBJECT BASED ON THE EXTENDED PHYSICAL OPTICS APPROXIMATION METHOD HAS BEEN PROPOSED. IT HAS BEEN INDICATED THAT THIS NEW METHOD IS VERY EFFECTIVE FOR THE AXIALLY SYMMETRIC SCATTERER. WE ARE PLANNING TO EXTEND THIS METHOD TO THREE DIMENSIONAL OBJECT.4. THE TRANSIENT RESPONSE OF A DIPOLE ANTENNA PLACED NEARBY THE INFINITE CONDUCTING CYLINDER HAS RIGOROUSLY ANALYZED FOR THE PURPOSE OF OBTAINING THE INVERSE SCATTERING ALGORITHM FOR VERY LONG CONDUCTING SCATTERER.