High-altitude electromagnetic pulse (HEMP) poses a serious threat to the electronic devices. According to the problem that the HEMP standards include the general wave characteristics in the free space barely, the environmental characteristics of electromagnetic pulses near the ground with the HEMP incident plane wave perpendicular or oblique to the ground are studied and the electromagnetic environmental parameters are simulated, based on the finite difference time domain method. The result shows that, when the HEMP incident plane wave is perpendicular to the ground, the reflected field weakens the incident one, which makes the total field depressed, especially in the lower position over the ground, and almost integer incident and reflected fields occur in the upper position. In the case of vertical polarization plane wave when the HEMP incident plane wave is oblique to the ground, horizontal field amplitude becomes smaller and pulse width becomes narrower when the incidence angle increases. The experiment conclusions are able to provide guidance for the protection design of electronic devices on the ground.%高空核爆电磁脉冲(HEMP)对电子设备构成严重的威胁;针对国内外有关HEMP的标准中对波形的定义主要针对自由空间的问题,使用时域有限差分法研究了HEMP平面波垂直/斜入射地面时,地面附近的电磁脉冲环境特性,仿真计算了有关电磁环境参数;结果表明,HEMP平面波垂直入射时,较低位置处反射场削弱了部分入射场.使总场幅度降低,较高位置处经历较为完整的人射场和反射场的冲击;HEMP平面波斜入射时,在垂直极化情况下,随着入射角的增大,地面附近的水平场幅值变小、脉冲宽度变窄;实验结论有利于指导地面电子设备的电磁防护设计.
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