高功率微波在土壤中传播模型的建立及非线性传播特性研究

The propagation of high-power microwave (HPM) in soil results in changes of soil properties (such as soil ionization and variation of electromagnetic parameters, which are nonlinear behavior), and these changes in soil properties in turn counteract the HPM, decreasing the energy transmission efficiency. By analysising the dynamic ionization process of soil under HPM, a complete systems including electrical resistivity, other soil properties change dependency of time equations and the Maxwell equations are constructed and solved by employing Finite Difference Time Domain (FDTD) method. The FDTD differential scheme of the system equations and its stability condition as well as the numerical dispersion will be derived and analyzed. Furthermore, some improvements of FDTD algorithm is proposed and higher caculation efficiency of the FDTD is achieved by employing sub-regional (non-parallel) way, specifically for electromagnetic wave propagation through large space problems. Based on these studies, the soil propagation of ultra-wideband (UWB) high-power microwave, energy loss during propagation, the soil propagation of Repetition-Frequency HPM Pulses, soil dynamic ionization process as well as other nonlinear physical process will be investigated. The implementation of this subject will provide the actual reference for strong electromagnetic radiation protection, civil air defense projects, electronic information equipment protection, high-power ground-penetrating radar and high power source design, etc..

高功率微波（HPM, 脉冲峰值功率大于100MW）在土壤中传播时，会引起土壤特性的变化（如土壤发生电离等非线性变化），土壤特性的变化又将反作用于高功率微波，影响其能量的传输效率。通过对高功率微波作用下的土壤动态电离过程的分析，构建包括电阻率等土壤特性参量时变方程及麦克斯韦方程组构成的完备系统，采用时域有限差分（FDTD）方法对该系统进行求解，并且对该系统方程的FDTD差分格式的稳定性条件和数值色散问题进行推导和分析。采用分区域（非并行）计算的方式对FDTD算法进行改进，以提高FDTD计算大空间传播问题的效率。在这些研究基础上，对超宽带高功率微波的土壤传播问题、传播能量损耗问题、重复频率脉冲土壤传播问题、土壤的动态电离过程以及其它非线性物理过程进行研究。本课题的研究将对强电磁辐射防护、人防工程、电子信息设备防护、探地高功率雷达和高功率源设计等方面提供实际参考依据。

在国家自然科学基金项目“61201095”的资助下，研究团队针对高功率微波（high power microwave, HPM）的土壤传播特性进行了相关的研究。研究范围主要围绕项目申报书提出的研究内容开展。. 当高功率微波（脉冲峰值功率大于100MW）传播于土壤之中时，会引起土壤电离，土壤的电离会使土壤电阻率减小，土壤电阻率减小带来会反作用于HPM，使HPM衰减增大，影响其能量的传输效率。. 联合描述土壤电离和去电离过程的电阻率变化方程和Maxwell方程组构建了HPM土壤传播模型，该模型能很好地描述土壤在HPM作用下电离和去电离的整个动态过程。利用时域有限差分（FDTD）方法，对该模型进行中心查分，并进一步进行了数值仿真求解。. 在这些基础上，对窄带和宽带/超宽带（不同参数的高功率微波）的高功率微波源在土壤中的传播都进行了数值模拟。计算过程中，采用分段时域有限差分法，提高了计算效率，实现了高效数值算法研究。. 采用冲击电流发生器模拟了雷电电磁脉冲的土壤击穿过程，并对土壤电阻率进行了测试。由雷电电电磁脉冲和高功率微波脉冲频段的不同，实验结果仅部分可以借鉴。