Study On Propagating Character Of High Frequency EM Waves In Several Types Of Plasma Layers

Widely modern technology applications can be found in the research of interaction between high frequency electromagnetic waves and plasma layer, such as plasma diagnosis, plasma antenna, plasma cloaking, etc. The present thesis is mainly focused on the character study of interaction between several type of plasma and high frequency electromagnetic waves which includes gigahertz, terahertz and blackbody radiation far-infrared terahertz regime, such as the characterization of absorption, reflection and transmission of the plasma to the incident electromagnetic wave power, with effects of different plasma parameters.Firstly, a brief introduction is presented in Chapter1about the concept of plasma, the character of electromagnetic waves in partially ionized plasma, the typical cloaking technology, and the general situation of the plasma cloaking.Secondly, in Chapter2, the methods for the research are introduced as WKB and Finite Difference Time Domain.Then, in Chapter3, the WKB and Finite Difference Time Domain methods are used to study the power absorption of broadband terahertz electromagnetic waves in the partially ionized uniform unmagnetized plasma layer. The power absorption spectra for the two methods are accordant. Additionally in the magnetized plasma layer model, the effects on power absorption of the right and left circularly polarized waves are calculated with different applied magnetic field, collision frequency and electron number density, which depend on those parameters. The absorption gaps of right circularly polarized waves are studied.In Chapter4, a modified radiation source model is built up to study the interaction between electromagnetic waves and partially ionized uniform plasma, by introducing a perfect blackbody far-infrared terahertz radiation spectrum. The effects of black body radiation temperature, electron number density, and collision frequency on the relative power absorption and transmission spectra of black body terahertz radiation are studied under atmosphere condition with WKB method. The black body radiation character spectra with different radiation temperature can be decreased and modified by plasma layer, especially by increasing the electron number density and the collision frequency, being favourable to the plasma cloaking and the far-infrared countermeasure in terahertz frequency range. In Chapter5, by considering different typical electron density profiles, a multi slab approximation model is built up to study the power absorption of broadband (0.75-30GHz) right circularly polarized electromagnetic waves in a partially ionized nonuniform magnetized plasma layer. Based on the model, the power absorption spectra for six cases are calculated and analyzed with WKB method. It is shown that the absorption strongly depends on the electron density fluctuant profile, the background electron number density and the collision frequency. In low frequency regime, the electron density profile affects absorption more effectively, and in high frequency regime, the average electron density does. A potential optimum profile is also analyzed and studied with some particular parameters.In Chapter6, by considering different kinds of electron density profiles, the power reflection of broadband (0.75-30GHz) electromagnetic waves is investigated with Finite Difference Time Domain method in a partially ionized nonuniform unmagnetized plasma layer covering a metal plane. For different electron number density profiles in six cases, the effects of the incident wave frequency, background electron number density, and collision frequency between electrons and neutral gas on the reflection of electromagnetic wave are discussed. The numerical results of the power reflection spectra for the six cases indicate that the reflection strongly depends on those parameters. Also, it is found that the electron density profile is more important in low frequency regime and the average electron density is more important in high frequency regime. One potential optimum profile of those six cases for reflection reduction in both low and high frequency regimes is also analyzed and studied.Finally, in Chapter7, we conclude the thesis, present the creation points and prospects with a brief discussion.