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为了评估稳态等离子体推力器(SPT)羽流对微波造成的衰减和相位变化,使用二维轴对称的PIC-DSMC方法,在空间及室压6mPa的真空舱两种环境下,计算了SPT-100羽流场中的电子分布。在此基础上,通过分析特征频率和计算衰减因子、相位常数,估算了2,4,8,12.5GHz共4个频率微波穿过羽流场时的衰减量和相移。8GHz和12.5GHz微波未发现明显的衰减,相移为10°～120°。2GHz和4GHz微波在喷口附近衰减量范围为10～50dB。仿真结果表明,C波段和S波段在SPT羽流中容易发生衰减,而X波段以上的高频微波衰减量很小,同时这几个波段微波均发生较大相移。真空舱内6mPa背压下对衰减量的预测仅略高于实际飞行情况,但微波相移会有较大误差。
In order to evaluate the attenuation and phase change caused by steady-state plasma thruster (PMT) plumes on microwaves, a two-dimensional axisymmetric PIC-DSMC method was used to calculate the SPT -100 plume flow field electron distribution. On this basis, by analyzing the characteristic frequency and calculating the attenuation factor and phase constant, we estimate the attenuation and the phase shift of the 4, 4, 8, 12.5 GHz microwaves passing through the plume. No significant attenuation was observed for 8GHz and 12.5GHz microwaves with a phase shift of 10 ° ~ 120 °. The attenuation range of 2GHz and 4GHz microwave near the nozzle is 10 ~ 50dB. The simulation results show that C-band and S-band are easy to decay in the SPT plume, while the high-frequency microwave attenuation above the X-band is very small. Meanwhile, the microwaves in these bands have larger phase shifts. The prediction of the attenuation at 6mPa in the vacuum chamber is only slightly higher than the actual flight situation, but the microwave phase shift will have greater error.