微波在薄层等离子体中传输效应研究

为了准确预测再入飞行过程中等离子体对微波传输特性的影响,采用WKB方法、FDTD方法、平面波理论和薄层等离子体理论4种方法,结合粉末激波管上开展的试验研究了X波段和Ka波段微波在薄层等离子体中的传输效应。对于X波段,试验时激波马赫数为9.6、10.7和10.5;对于Ka波段,试验时激波马赫数为10.5。通过对比与分析获得的主要结论有：当等离子体厚度和入射波波长相近时,薄层等离子体理论计算结果比其它三种方法的计算结果更接近于试验结果;在碰撞频率接近并且电子密度小于临界电子密度的条件下,Ka波段微波信号穿过相同厚度的等离子体比X波段微波信号衰减小得多,具有更强的穿透性;如果等离子体碰撞频率和微波入射频率相同,随着电子密度的增加,微波信号穿过相同厚度的等离子体时衰减变大;当碰撞频率和入射波频率差不多时,共振吸收导致衰减达到最大值。

Research on microwave transmission in thin layer plasma

To accurately predict the attenuations of microwave transmission in plasma when a vehicle reenters the atmosphere, four methods, namely FDTD method, WKB method, planar wave theory and thin shockwave theory were used to research the effects of thin layer plasma on microwave transmission. The attenuations of microwave transmission in plasma were simulated and compared with experimental results. To X band tests, the Mach numbers of shock waves are 9.6, 10.7 and 10.5, respectively. To Ka band test, the Mach number of shock wave is 10.5. The results show that the data given by thin shockwave theory are closest to experimental results than other methods when plasma thickness is near to wavelength. Ka band transmission attenua- tion is smaller than X band transmission attenuation when they propagate in the plasma with the same electron density and collision frequency. The microwave attenuation will be larger with the increase of electron density when microwave propagates in same thickness plasma. The attenuation will be largest when collision frequency is near to microwave frequency.