A Study On The Reflection Of Electromagnetic Waves In Plasma And Its Application

In recent years, aerospace technology had gained a tremendous improvement. In this improvement people often get access to plasma. For example, when spacecraft return to earth form outer space through the atmosphere, when hypersonic plane flies in stratosphere, and when people get study on plasma stealth, there are plasma. In this situations above, electromagnetic reflction and attenuation caused by plasma always do benefits or harm. Therefore it is necessary and meaningful to do research on the reflection plasma to electromagnetic waves.First of all, this paper analyse the electromagetic reflection and attenuation caused by static plasma coated on the PEC, and a numerical calculation on power reflection coefficient is made on FDTD method. It turns out that the reflection of some EM-waves in the static plasma whose frequence is in a certain bandwidth is ceasing, and to others is strong. And the density of electrons, frequency of collison, thickness of plasma affect the location and width of the bandwidth and the smallest reflection coefficient.Secondly, this paper presents the effect on the mono-frequency and muti-frequency electromagnetic waves in frequency domain caused by saltational and sinusoidal time-varying plasma. And a numerical computing of FDTD method is done.The result shows that saltational time-varying plasma push the frequency to the higher place at the moment the density of electrons of plasma is changing. And this new frequency is occurred on the moment plasma is changing. And the sinusoidal time-varing plasma will arise some parasitical frequencies, and the basic electron density, changing range and changing frequency of the sinusoidal time-varying plasma affect the amplitudes, the positions and the amout of the parasitical frequencies.Finally, with the ground of influence of plasma to radar range finding,this paper analyse the affect of the static plasma and time-varying plasma on radar range finding. And a numerical compution is made as well. The consequence shows that the effect of static plasma to measuring is very small, and the sinusoidal plasma will lead to the wrong signals. And the changing frequency affect the position of the wrong signals, and the basic electron density and changing range affect the strenth of the wrong signals.