Study On The Attenuation Transmission Of Electromagnetic Waves In Plasma

"Blackout" is a very important problem that needs to face in the development of aerospace industry.It refers that the hypersonic flight vehicle is returning to Earth when entering the atmosphere,the plasma sheath will form a certain thickness on the surface of the vehicle which leads to the signal interrupted in a certain period of time.The existence of "Blackout" makes it impossible for the ground monitoring equipment to proceed real-time communication and tracking of aircraft which has adverse effects on the safe flight of the aircraft and the search and rescue on the ground.In recent years,the continuous development of terahertz(THz)source and THz antenna added a new research method for us to solve the "Blackout" problem.In this paper,Terahertz(THZ)wave is used as communication carrier to study the propagation characteristics of THz wave in various plasma environments.The main contents of this paper are as follows:(?)In the transmission model framework for unmagnetized plasma and under the two cases of THz wave vertical and oblique incidence,the performance differences of energy attenuation of terahertz wave under uniform and unmagnetized collisional plasma environment are studied varying with the change of plasma density,plasma collision frequency and terahertz wave frequency,respectively.(?)In this paper,three kinds of plasma sheath models,Linear distribution,Epstein distribution and Gaussian distribution,are established for the analysis of propagation characteristics in inhomogeneous plasma environment.With the help of the model frame of THz wave propagation in inhomogeneous and unmagnetized plasma,the theoretical simulation is carried out by using the continuity condition of electric field and magnetic field at the boundary of each layer.The difference of the energy attenuation of THz wave with different plasma collision frequency and peak electron density(Nemax)is discussed.The simulation results show that the energy decay of the THz wave increases with the enlargement of the peak electron density,but not with the collision frequency.The rate has been increasing with the enlargement of the rate.(?)In this paper,two transmission models of THz waves in inhomogeneous and magnetized plasmas are established.The different effects of applied magnetic field intensity on the energy attenuation of THz wave are discussed.The energy decay of magnetized plasmais mainly caused by two aspects.One is caused by collision attenuation and the other is caused by electron cyclotron resonance attenuation or high hybrid attenuation.The simulation results show that when the frequency of THz wave avoids the cyclotron frequency corresponding to the external magnetic field intensity or the high hybrid frequency,the attenuation value of THz wave is almost equal to zero d B.In this case,the THz wave can penetrate the plasma to communicate with the ground in real time.In conclusion,the theoretical derivation and simulation of THz wave in various kinds of plasma are studied in this paper,which provides a good theoretical basis and relevant parameter reference for alleviating the problem of communication interruption under plasma sheath.It is of great significance and application value to solve the problem of “Blackout” in the future.