机载探地雷达数值模拟及逆时偏移成像

Airborne ground penetrating radar numerical simulation and reverse time migration

机载探地雷达可以用于人类无法到达的危险地区、植被严重覆盖的地下目标体探测,然而由于机载探地雷达的特殊性,影响机载探地雷达探测效果的因素包括天线的极化方向、天线的飞行高度以及地表粗糙度等.为了研究这些影响因素与探测效果之间的关系,用三维时间域有限差分模拟电磁波的传播过程,以沙漠地区地下空洞掩体的机载探地雷达探测为实例,分别模拟了不同天线极化方向、天线高度及地表粗糙度情况下的机载探地雷达剖面,分析了各因素对机载探地雷达探测地下空洞目标体的影响.天线极化方向与目标体走向垂直更有利于地下目标体探测;天线距离地表越近,可以获得更高分辨率的雷达剖面;沙漠地表起伏越大,雷达剖面中的散射杂波能量越强,浅部地下目标体信号容易被掩盖.为了消除起伏地形造成的散射杂波,提出用逆时偏移成像技术对共炮集机载探地雷达数据进行偏移成像,成像结果优于基尔霍夫偏移成像结果.

Airborne ground penetrating radar （GPR） could be used for detecting underground targets in dangerous area or vegetation heavily covered area. Because of the particularity of airborne GPR, the detecting results are influenced by the antenna polarization, antenna height and the ground roughness. In order to assess their influence on the detecting results, we modeled electromagnetic wave propagation by using three dimensional finite difference time domain （3D- FDTD） method, simulated the cavity bunker detecting in desert area by using airborne GPR. We separately simulated the radar profile at different antenna polarization direction, different antenna height and different surface roughness, and analyzed the effect of each factor on the airborne GPR detection. Better radar image could be acquired when the antenna polarization direction is vertical to abnormal orientation; if the antenna height is more closer to ground surface, higher resolution radar image could be gotten; as the desert surface roughness increases, the energy of the scattering clutter in the radar profile becomes stronger, the target signal from shallow object could be easily flooded. In order to eliminate the scattering fluctuations due to terrain clutter, we proposed to use reverse time migration imaging technology from the reflection seismic to process the common shot gather airborne GPR data, thus eliminating the surface scattering clutter due to terrain.