Tunable Cherenkov High Power Microwave Output Based On Changing Parameters Of The Filling Dielectric

In recent years,high power microwave devices have witnessed great progress in many aspects,such as multiband and high efficiency,which attracts much concerning.However,restricted by the physical mechanism and material technology,Cerenkov type device adopt many methods,adding inner coaxial structure or changing resonant cavity structure parameters etc,to realize tunable microwave output.In this dissertation,a novel Cerenkov oscillator is proposed to make the microwave output tunable by changing the filling dielectric parameters in slow wave structure.This kind of Cerenkov oscillators which could be filled by liquid dielectric,have periodic dielectric slow wave structures,possessing advantages as free disassembly,wide tunable range.Detailed elaborations for this novel Cerenkov oscillator are presented in three aspects,that is,theoretical analysis,Particle-In-Cell simulation,engineering design.The main contents are as follows:After a systematic investigation of various existing tunable Cerenkov oscillators,their working performances and structure characteristics are analyzed,and advantages and disadvantages in tuning are compared,to come up with a solution to tune Cerenkov high power microwave output by changing filling dielectric parameters.Dispersion curves of cylindrical waveguide filled with homogeneous dielectric are obtained by theoretic analysis,which comes to a conclusion that output microwave frequency has relationship to dielectric permittivity.Furthermore,dispersion curves for cylindrical waveguide disk-loaded with dielectric are solved,which resemble former models mentioned.Finally,ideas presented in this project are completely proved to be feasible in theory.A dielectric slow wave structure type Cerenkov oscillator is designed by adopting a Particle-In-Cell simulation software.In the prime simulation,a series of microwave output frequency of 5.79 GHz,9.19 GHz and 7.09 GHz and a series of microwave output power of 0.8GW,0.9GW and 1.1GW are obtained when relative dielectric permittivity are 1.2,19 and 31.5 respectively.After adding rectangle dielectric diaphragm,shortening emitter length,deepen cavity resonator size,a series of microwave output frequency of 10.69 GHz,7.46 GHz and 6.89 GHz and a series of microwave output power of 0.8GW,0.9GW and 1.1GW are obtained when relative dielectric permittivity are 30,40 and 65 respectively.After adding a quartz glass dielectric packaging structure with dielectric permittivity of 3.7 to the dielectric slow wave structure,a series of microwave output frequency of 6.89 GHz,10.05 GHz and 7.31 GHz and a series of microwave output power of 0.9GW,1.1GW and 1.0GW are realized with relative dielectric permittivity of 15.7,34.3 and 42.0 respectively.Then,the output average power vibration in the simulation gets good explanations by a dual-frequency microwave compounding model.Finally,after a fitting of dielectric permittivity and output frequency within a certain range,it can be concluded that the output frequency near the resonant point is inversely proportional to relative dielectric permittivity linearly and it is more effective to tune output frequency by adjusting dielectric permittivity in the low dielectric permittivity range.In the engineering design,we select liquid electric to be to filling dielectric.Propose a means to meet the need of continuously adjusting dielectric in wide range by mixing two kind of dielectric together,one in much high permittivity and the other one in low permittivity.With the model of Debye,we analysis and calculate the relative permittivity real part range of NaCl solution,which approve the feasible of the above method.Then,analysis and calculate the relative permittivity real and imaginary part of mixture solution of propylene carbonate and benzene in details,proving the real part of this dielectric can meet the need of engineering in the frequency range between 6GHz and 10 GHz.Its loss tangent is range from 0.1 to 0.2 in that band.Finally,the engineering is given out,and the operating procedures and specification of this novel Cerenkov oscillator are formulated.