半空间模型的地下目标成像

Imaging of underground objects based on half-space model

由于电磁波在穿越不同介质时会出现折射现象,因此在对地下目标成像时,电磁波信号在穿越从雷达到达地下目标的组合通道时,路径不是直线而是折线,此时利用常规的自由空间中的合成孔径成像方法已经不能对目标进行成像。为此,基于电磁波的传播规律和地层有耗媒质的特性,提出了电磁波传输的半空间模型,使其能够充分反映电磁波信号在整个传播过程中的真实路径,并得到了相应的目标回波表达式。将其应用到机载条件下的地下目标成像之后,通过仿真比较,可以明显看出,使用半空间模型对地下目标成像效果有改善,验证了半空间模型适用于对分层土壤中的地下目标成像。

Because of the refraction of electromagnetic wave when it traversing different medium, the route of the signal from airborne radar to underground object is not a straight line but a curve. Thus the routine SAR imaging method in free space is not suitable for the imaging of underground objects. Based on spread rule of electromagnetic wave and characteristics of stratum loss medium, half-space model of electromagnetic wave transmission is proposed, which can be used to reflect the whole true route. When the model is used in imaging of underground objects we gain the expression of echo. The effects of imaging before and after using half-space model are compared by simulation. It is showed that the half-space model is fit for imaging of underground objects.