Simulation And Experimental Study On Microwave Scattering By Different Shaped Plasmas

Plasma is a kind of special electromagnetic material with quasi-neutral character and has unique electromagnetic properties in micro-scale with respect to traditional dielectrics when interacting with electromagnetic waves.The scattering property of plasma on microwaves is the basis of applications such as aircraft radar stealth,electromagnetic pulse protection,re-entry "black barrier" issue,and so on,and is therefore very important to theoretical investigation and practical use.In this paper,the scattering effects of different shaped plasmas on microwave propagation are studied in simulation based on finite difference time domain(FDTD)method.The absorption and scattering of microwaves are also experimentally verified in high-density plasma generated by hollow cathode discharge(HCD).Firstly,the scattering property of planar plasma with different thicknesses and frequencies on microwaves is investigated in numerical simulation.The transmission power of microwaves after passing the high-density plasma planar are measured experimentally.The results show that the plasma density(frequency)and thickness have a great influence on the scattering and absorption of microwaves.The higher the plasma frequency is,the greater the microwave cut-off frequency will be.Secondly,the scattering effects of a non-uniform plasma column and column array on microwave are investigated through numerical simulations,and the microwave transmittance after getting through a high-density plasma generated by a ring-shaped hollow cathode and a plasma array constituted by plasma columns is measured experimentally by using a vector net analyzer.The results show that the distribution of plasma density in columns agrees well with that obtained in simulation,i.e.,the microwave scattering in symmetric angles around±15°.Plasma array arranged well can replace effectively large-area plasma planar.But the plasma density should be appropriate to take a remarkable effect on microwave reflection.Finally,the scattering properties of 3D spherical and ellipsoidal plasma on microwaves are simulated numerically.Comparing with the case of 2D plasma column,the scattering angle increases from 15° to 30°.The length of shorter axis and density of ellipsoidal plasma can significantly affect the scattering angle.The power of scattering wave,together with its scattering angle,increases first and then decreases with the increase of shorter axis and plasma density and will be constant when the plasma density is large enough.