等离子体绕流场电磁波传输特性分析

Analysis on electromagnetic wave propagation in plasma flow field

本文分析了等离子体绕流场中电磁波传输特性随几个主要物理参数的变化规律,包括电子密度、谐振频率、碰撞频率等。通过时域有限差分(finite-difference time-domain, FDTD)方法进行了仿真,结果表明在典型仿真输入条件下,在米波至毫米波波段,随着谐振频率升高,等离子体绕流场反射率升高、透射率降低;在米波至厘米波波段,随着碰撞频率升高,等离子体绕流场反射率降低、透射率规律性不显著;在毫米波波段以上,等离子体绕流场的反射率和透射率与碰撞频率关系不大,而且反射很弱,以透射为主。目标飞行高度在30~50 km且速度在5 000 m/s以上时,目标驻点处等离子体绕流场对S、C、X波段有显著的衰减作用,影响雷达探测或产生黑障现象。开展了基于高焓激波风洞的等离子绕流场电磁特性测量实验,获取了C、X波段雷达散射截面(radar cross section,RCS)数据和绕流场电子密度数据,并利用其验证了仿真结果的正确性。

In this paper,the main parameters of plasma flow field related to electromagnetic wave propagation are analyzed,including electron density,resonant frequency,body collision frequency,etc.Some simulations are carried out with the finite-difference time-domain(FDTD)method.The results show that the reflectivity of electromagnetic wave increases and the transmissivity decreases with the increase of resonant frequency from meter-wave bands to millimeter-wave bands in the typical case.The reflectivity decreases with the increase of collision frequency from meter-wave bands to centimeter-wave band,while the regularity of transmissivity is not significant.Above millimeterwave band,the reflectivity and transmissivity of plasma flow field is not related to collision frequency.Its reflection is weak,and the transmission is dominant.When the target height is 30−50 km and the speed is higher than 5000 m/s,the plasma flow field near stagnation point has a significant absorbing effect on electromagnetic waves at S band,C band,and X band,resulting black barrier or radar echo attenuation.The experiment of measuring electromagnetic characteristics of plasma flow field based on high enthalpy shock wave wind tunnel was carried out.The C and X-band RCS data and electron density data of plasma flow field were obtained,and the correctness of simulation results was verified by the experimental data.