Microwave propagation with the gas breakdown

Abstract

By combining the microwave propagation theory and the gas breakdown theory, the microwave propagation with the gas breakdown is analyzed theoretically. Particle-in-cell/Monte Carlo collision (PIC/MCC) simulations are carried out to verify the theoretical results. Based on this theoretical method, the breakdown phenomenon of the pulse microwave is analyzed. The results show that the product values of the initial electron density and the propagation length are the criterion to distinguish the pulse peak decline breakdown and the pulse width reduction breakdown. Furthermore, the energy transmission is also studied, which shows that the total output energy is approximately independent of the input electric field if the electric field is not extremely large.

Effect of air breakdown on microwave pulse energy transmission

“…The plasma produced in the air breakdown hinders strongly the microwave pulse energy transmission, since it absorbs and reflects the microwave pulse. [3][4][5][6] Consequently, it is very important to study and understand the effect of the air breakdown on the pulse energy transmission.…”

Vertical Line Array-level Signal-to-noise Ratio Varying with Source Depths in the Presence of Surface Noise

“…计阵列信号处理理论推导得到了一系列基于垂直阵接收数据的目标检测、 定位及 辐射声功率估计算法，很大程度上提高了风成噪声背景下的被动声纳处理性能 [13][14][15][16][17][18] 。然而，这些研究大多关注的只是算法设计本身。与感兴趣的目标辐射声波 相同，风成噪声也是通过源辐射、波导传播到达接收阵，因此，它也具有与前者 相类似的多模态结构。即，根据简正波理论 [5,19] ，声源激励的声场可以分解为若 干阶简正波之和的形式， 各阶简正波对声场的贡献与声源深度上该阶简正波对应 的模深函数幅度成正比。由于风成噪声源位于海面附近，对应的低阶模态幅度非 常小， 因此， 风成噪声很少对应低阶模态、 其大部分能量都来源于中高阶模态 (这 也是"噪声凹槽"出现的本质原因) ，尤其是在负声速梯度环境中 [20] 。而另一方 面，信号场对应的模态结构与声源深度息息相关；随声源深度的变化，风成噪声 场与信号场两者之间的模态结构差异势必发生变化， 进而导致算法性能也出现一 定的变化。 这一变化为何？是否存在一些特定的变化规律？以上问题的答案对于 声纳设备的使用以及目标机动隐蔽具有重要的指导意义， 但时至今日也未见于公 开发表的文献。 本文则针对以上问题开展研究。考虑到无论是对于目标检测或是参数估计， 阵列信噪比(Signal-to-Noise Ratio, SNR)--计入了垂直阵采样声强、背景噪声 功率、阵处理增益--都是决定处理性能最关键的物理量 [13][14][15]21] ，因此，本文将 研究聚焦于风成噪声背景下垂直阵采样 SNR 随声源深度的变化上。我们将在 K-…”