Research On High-power Microwave Plasma Phase Shifter Technology

In the high-power microwave phased array antenna system,the method of controlling the excitation phase of the radiation array element is used to realize the widerange beam scanning of the radiation system.With the development of technology,the high-power microwave system puts higher requirements on the power capacity,structure layout,transmission characteristics,working bandwidth,phase-shifting speed and other characteristics of the phase-shifting unit.Several kinds of phase shifter are developed in past decades.However,those phase shifters used in conventional situation cannot be directly applied in high-power microwave system due to the limitation of electric breakdown,transmission loss and other problems.Thus,it is urgent to carry out systematic and in-depth research on phase-shifting units suitable for different phased array systems,so as to achieve a breakthrough in new phase-shifting mechanism,new devices and new media.To meet the requirements of high-power microwave phased array antenna system,it is necessary to design a new type of electronically controlled phase shifter with high power capacity and fast response speed.Plasma has characteristics of controlled scattering and reflection of microwave,and the time of excitation and quenching is very short.And it cannot interact with microwave before excitation.Therefore,phase shifters can be designed by the nature of plasma.The use of plasma can overcome the problems of common phase shifters as slow phase-shifting speed,poor flexibility and strong interaction with electromagnetic wave.Based on these characteristics of plasma and the actual requirements of high-power microwave phased array antenna,a new type of phase shifter with plasma as the medium is proposed in this paper.The work on analysis,design,simulation and experimental research are also carried out.The main work of this paper includes the following aspects:1.The mechanism of controllable plasma phase shifting is studied,and the relationship between the key parameters of plasma phase shifter and its power capacity is analyzed.Plasma is the adjustable microwave reflection medium of phase shifter.The characteristics and control methods of plasma directly affect the performance of the phase shifter.Based on the theory of plasma-microwave interaction,this paper explores a new method to control the phase-shifting under different conditions.The main factors that limit the power capacity of microwave transmission are studied theoretically.And the excitation methods and control strategies of plasma with different densities under different gas composition and pressure are studied emphatically.We also analyzed and calculated the relationship between the power capacity and the structure parameters of the plasma phase shifter according to the requirements of phase-shifting characteristics.The results show that the power capacity of this S-band plasma phase shifter can reach more than 20 MW and the motion time of arbitrary beam pointing can be reduced to milliseconds.In addition,the power capacity of the phase shifter can be further increased by optimizing the structure and gas parameters.2.The electromagnetic simulation and particle simulation of the plasma phase shifter are carried out;the structure and strategy of the shifter are further optimized based on simulation.The structure design and electromagnetic simulation of the plasma phase shifter are carried out to verify the new structures of the shifter,and to meet the application requirements of phased arrays with different architectures.In terms of structure design and phase shifting strategy,the beam pointing accuracy of the optimized four-column plasma phase shifter is improved to 1/4 of that of the original one;in particle simulation,the process from local excitation to full excitation is simulated,and the influence of different parameters on the performance of the plasma phase shifter is also simulated,and the feasibility of plasma applied to high-power microwave phase shifter is proved.3.A scheme for controlling plasma in high field environment is proposed.The excitation and quenching of plasma need to be precisely controlled,which is the premise of being applied as an effective phase-shifting medium.Based on the case of high-power microwave,this paper proposes a novel scheme to control plasmas under high-field intensity: high-voltage electric field and high-power microwave combined excitation.By placing quartz tubes filled with high-pressure gas in the waveguide,a local plasma is generated by high-voltage excitation,and then the rapid diffusion and saturation of the plasma is realized by strong electric field of high-power microwave.Finally,effective reflection of high-power microwave is achieved.This scheme can solve practical problems of the rapid control of phase shift medium in high electric field gradient environment and lay a foundation for the development of new types of highpower microwave phased array system.4.The verification device of plasma phase shifter is designed and installed;the experimental platform is built and some verification high-power experiments are carried out.The principle verification device of the plasma phase shifter is designed and fabricated.The physical and technical problems related to the verification model are solved.The theoretical and simulation results of the subject are preliminarily verified by experiments.These experiments verify the feasibility of the excitation method and the fast control of plasma,and realize the process of interaction between microwave and plasma,which lays a foundation for the following experimental study of the high-power microwave plasma phase shifter.