探地雷达反射波研究

Research on Ground Penetrating Radar Reflected Waves

【目的】研究探地雷达电磁波在介质中的传播规律。【方法】首先,在薄层物理模型基础上,分析入射波经薄层多次反射、折射后总的反射波信号与一次反射波信号,得到入射波经过薄层后的反射能量变化情况。其次,在理论分析基础上,对该反射能量变化进行数值分析,通过特征曲线可以直观地得到薄层的电磁波反射特性。【结果】在入射波频率确定时,入射波在薄层传播的双程走时与薄层厚度呈正相关,且不论上厚层、下厚层和薄层的相对介电常数如何取值,经过薄层后的反能量变化均在较低Δhλ和较高Δhλ范围内得到加强,在中间Δhλ范围内被抑制。【结论】雷达发射的电磁波在经过薄层后,一部分频率成分的波得到加强,另一部分频率成分的波被抑制,即薄层对探地雷达发射的电磁波有滤波作用,且薄层的介电常数对该滤波作用会产生影响。

[Purposes]The propagation law of ground penetrating radar electromagnetic wave in medium is studied.[Methods]Firstly,based on the physical model of the thin layer,the theoretical analysis method is used to analyze the total reflected wave signal and the primary reflected wave signal of the inci⁃dent wave after multiple reflections and refraction of the thin layer,and the change of the reflected en⁃ergy of the incident wave after passing through the thin layer is obtained.Secondly,based on the theoreti⁃cal analysis,the numerical analysis of the reflection energy change is carried out.Finally,the electromag⁃netic wave reflection characteristics of the thin layer can be obtained intuitively.[Findings]When the in⁃cident wave frequency is determined,the two ways travel time of incident wave propagation in thin layer is positively related to the thin layer’s thickness.No matter the relative dielectric constant of the upper and lower thick layers and thin layers in any numbers,the inverse energy change were enhanced in both the lowerΔhλand higherΔhλranges and were suppressed in the middleΔhλ,when it crossing through the thin layer.[Conclusions]When the electromagnetic waves emitted by radar crossing through the thin layer,some of the waves in a certain frequency component were enhanced and the other waves were suppressed.In other words,the thin layers have a filter function for the waves which are emitted by the ground penetrating radar.The dielectric constant of the thin layers has an effect on the filter function.