Research On Microstrip Meander Line Traveling Wave Tube Based On Periodical Metallic Rods

Travelling wave tubes(TWTs)have excellent performance in high power,wide bandwidth and high efficiency.Therefore,it is widely used in electronic countermeasures,satellite,radar and other fields.TWTs have expand the frequency to Ka-band(27GHz-40GHz),which has the advantages of wide bandwidth,less interference,and small device size.With the gradual increase of the working frequency,the traditional processing technology can't meet the requirements of such small-sized slow wave structure(SWS).The emergence of microstrip meander line(MML)TWTs conforms with the development trends of miniaturization,planarization,and light weight of TWTs.MML TWTs have advantages of wide operating bandwidth,low operating voltage,and high electronic efficiency.It can provide medium-level output power and has a broad development prospect and research significance.Meanwhile,MML SWS structure is based on the planar micro-circuit technology,and it is fabricated on the dielectric substrate.Thus,it obviously has the problem of dielectric charging,which greatly affects the design and usage of the MML TWT.In order to decrease the problem of dielectric charging of MML,a novel MML SWS based on periodical metallic rods(PMRs),according to the theory of metamaterial and substrate integrated waveguide(SIW),is proposed in this thesis.The simulation and cold-test characteristics show that the PMR structure can significantly increase the metal coverage area of the SWS and reduce the divergent electrons accumulated on the dielectric substrate.Meanwhile,the dispersion characteristics of the SWS is flatter than that of MML and the phase velocity can be reduced.Moreover,the experimental results verify the transmission performance of the MML with PMR(MML-PMR)with simulation results.The test results of the vector network analyzer are in good agreement with the simulation results of the CST software.In order to further analyze the influence of PMR structure on the performance of MMLPMR TWT,Particle-in-cell(PIC)simulations of a conventional MML TWT and a MML-PMR TWT are carried out in this thesis.Using the optimized parameters obtained by cold-test simulation,the PIC simulation results show that the PMR structure can significantly improve the output power and RF efficiency of the MML TWT,and can decrease the dielectric charging problem.MML-PMR TWT can provide 66 W output power at 30 GHz.The maximum gain is 26.74 dB,and the RF efficiency can be increased to 12.79%.