摘要
从时变媒质中的麦克斯韦方程出发,首先推导出线性、均匀、各向同性的时变媒质中电场和磁场波动方程的一般表达式,然后应用有限差分法,推导出一般情况下电场的时间推进计算公式,计算得到了一种电导率随时间正弦变化:σ(t)=a1+a2sin2πf s t的电场数值解.结果表明,在该电导率时变媒质中传播的电磁波的电场有明显的衰减现象;当电导率的振荡频率等于电磁波的初始频率时,系数a1的增加将导致电场幅度的衰减加快,而系数a2的增加对电场幅度的衰减速度几乎没有明显的影响;当系数a1和a2不变且电导率的振荡频率为10n倍的电磁波的初始频率时,电场衰减速度与电导率的振荡频率呈现非线性的关系,计算结果表明:当电导率的振荡频率f s=2.45×108GHz即10-1倍的电磁波的初始频率时,电场的衰减最快.另外,电场衰减过程中频率没有改变,故在此电导率正弦时变媒质中传播的电磁波不存在"频移现象".
From the Maxwell curl equations in homogeneous and uniform time-varying media, the wave equations in source free region are firstly derived when conductivity of media is time-dependent. The characteristics of wave propagation in the media whose conductivity is an sinusoidal function of time, function as σ（t）=a1＋a2sin2πf, t , has been simulated by finite-difference method. Results show the attenuation phenomena in the amplitude of the electric field, and the attenuation caused by rising of al are more obvious than rising of a2 when a1 and a2 change and the oscillation frequency of conductivity is equal to the initial frequency of conductivity. In addition, when the oscillation frequency of conductivity is varying as f, = 10^nf0 where f0 = 2. 45×10^9 GHz, the initial frequency of wave, and the attenuation rate of the amplitude of electric field intensity have nonlinear change with the rising of fs, and the electric field intensity of wave has the greatest attenuation rate as f, = 10^1f0 = 2. 45 ×10^8GHz. Furthermore,the ＂frequency shift＂ phenomenon does not exist in the conductivity- sinusoidal -time-varying media .
出处
《西南民族大学学报（自然科学版）》
CAS
2015年第2期229-233,共5页
Journal of Southwest Minzu University(Natural Science Edition)
基金
supported by the Fundamental Research Funds for the Central Universities, Southwest University for Nationalities, No 11NZYQN17~~
关键词
时变媒质
有限差分法
电波传播
衰减
振荡
time-varying media
finite-difference method
wave propagation
attenuation
oscillation
