Considering the series effects of high power microwave such as thermal fast electrons effect, collision frequency effect and ionization frequency effect, a unified high power microwave (HPM) propagation model is presented in this paper. A unified air-breakdown model for single-pulse HPM is discussed in detail and the breakdown threshold is determined. It is found that the frequency of plasma induced by high power microwave is greater than previous value. The threshold of air breakdown increases with altitude increasing under the same condition. When the threshold reaches a minimum, a reverse trend will appear. And the minimum value will be obtained in an area of 30-60 km. The typical phenomenon waveform and threshold are gained in the experiment of air breakdown in microwave darkroom. And a well uniform distribution of the air breakdown threshold is shown theoretically and experimentally.%综合考虑高功率微波强电场作用下的热致快速电子效应、碰撞频率、电离频率等充分体现高功率微波特性的参量模型,基于高功率微波混合大气传输模型,提出了单脉冲高功率微波混合大气统一非线性击穿模型,定义了单脉冲高功率微波击穿阈值.理论研究结果表明:考虑中性气体分子极化作用以及电子的碰撞热效应后,大气击穿时对应的等离子体频率明显变大;大气击穿阈值随高度的增加先逐渐减小然后增大,在30-60 km区域存在一个极小值.开展了X波段窄带高功率微波单脉冲大气击穿实验研究,得到了典型条件下的高功率微波击穿现象、波形和阈值,且与理论结果一致性较好.
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