Research On L-band Transparent Cathode Relativistic Magnetron

High power microwave technology has great application prospects in scientific research,national defense,military,communications,aerospace and civil fields.Relativistic magnetron is one of the most mature high power microwave sources.Relativistic magnetrons are mainly studied in S band and C band at home and abroad.Considering the important national defense and military application value of L band RM,this paper makes a preliminary study of L band RM.At the same time,the application of RM requires not only high power,but also rapid starting of RM,while the traditio na l cylindrical cathode RM generally has slow starting and low efficiency.The use of transparent cathode can accelerate the vibration of RM,so the study of the working mechanism of transparent cathode has important guiding significance for the applicatio n of transparent cathode.Firstly,the working mechanism of transparent cathode is analyzed theoretica lly,and then the influence of the change of transparent cathode on the static field and electronic trajectory in RM is analyzed.The results show that with the increase of the degree of the cathode blade,the amplitude of DC angular electric field near the surface of transparent cathode decreases gradually,and the time spent by electrons from cathode to anode increases more and more.With the increase of the number of cathode blades,the same change rule is also observed.The amplitude of DC angular electric field is the largest when the position of transparent cathode blade is positively opposite to the anode block.Then the influence of RM structure change on resonance frequency is analyzed by dispersion analysis.The influence of structure change on RM output performance is studied by PIC simulation.A L-band RM structure with good performance is obtained,and the output frequency is about 1.3GHz.On this basis,PIC simulation studies the influence of the change of transparent cathode on the output performance of RM.The simulation results show that different transparent cathode RMs have different starting speed,which is mainly due to the different amplitudes of DC angular electric field near the surface of transparent cathode and the different surface area of cathode emitted electrons.The larger these two conditions are met at the same time,the faster RM will start.When the degree of transparent cathode blade is 30 degrees,the number of blades is 2 or 3,the angular position is positive to the anode block.The starting speed of RM is the fastest,which is about 38%~39% faster than that of RM using cylindrical cathode.Finally,according to the simulation results,an L-band RM structure and four transparent cathode structures are designed and fabricated,and their experimental tests are carried out.The experimental results show that the resonance frequency of RM is about 1.33 GHz;compared with the traditional cylindrical cathode,all kinds of transparent cathodes can accelerate the start-up of RM,and the fastest speed is 30.23%.Compared with the cylindrical cathode,the output power and efficiency of RM are improved with the use of six surface transparent cathodes of 30 degrees,and the start-up speed is also increased by 25.58%.The experimental results confirm the correctness of the simulation results.The output performance of RM can be improved by choosing the appropriate number of cathode blades and the degree of cathode blades.