Research On The Cross-band Tunable Magnetically Insulated Transmission Line Oscillator

With the advantages of high level of microwave power,no magnetic field and compact configuration,magnetically insulated transmission line oscillator(MILO)is one major hotspot in the field of high power microwave(HPM)source research at present.Traditional MILO,which belongs to typical arrow-band HPM device,can not adjust its output frequency.Broadband frequency tunning,however,has become one of the most important development directions in the research on theory and application of MILO.This thesis puts forward a cross-band tunable MILO system(CTMILOs),which consists of a tunable MILO,a tunable mode converter and a broadband radiation device.The main research contents include the following aspects:1.Theoretical studies of the MILOThe thesis introduces the basic principles and processes for slow wave structure(SWS)in system,based on which,the 1.757 GHz load-limited MILO is designed.On the basis of the model,we focus on the study of self-magnetic property,beam-wave interaction,and so on.Next,we do key research on the frequency tunning performance and the power efficiency,and analyze the tunning feature of microwave frequency,normalized phase velocity,mode separation,coupling impedance in the tunning process,to seek for the superior methode which can ensure both stable work and high power efficiency.Specifically,the tunning mechanism added to the traditional MILO can change the outer radius of the SWS,and consequently change the microwave frequency.These researches lay a firm foundation for the structural design of the MILO.2.Simulation studies of MILOThrough simulation and optimization,a 1.757 GHz load-limited MILO is obtained,and its eigenmode,quality factor and hot test characteristics are analyzed.When the applied voltage and input power are 590 k V and 29.0 GW,respectively,HPM is generated with an output power of 5.0 GW,a frequency of 1.575 GHz,a power efficiency of 17.2%.Under the same input electrical parameters,we pay attention to the frequency tunning performance and the power efficiency of the MILO,which get the maximum power efficiency of 20.1%with an output power of 5.6 GW,a frequency of1.425 GHz.The 3 d B tunable frequency range is 2.12?0.85 GHz and the 3 d B tunning bandwidth is 85.5%.a MILO with uneven vanes is put forward and simulated.The typical simulation results are as follow.When the applied voltage and input power are 586 k V and 28.7GW,respectively,HPM is generated with a maximum output power of 7.1 GW,a frequency of 1.440 GHz,and a power efficiency of 23.7%.Under the same input electrical parameters,the 3 d B tunable frequency range is 0.95?2.05 GHz and the 3 d B tunning bandwidth is 73.3%.A high-efficiency MILO(HEMILO)with ridge-disk-loaded vanes is put forward.After physical analysis and hot test,it is verified that the ridge of the HEMILO can improve the power efficiency effectively as well as have none worse influence on tunning performance.When the applied voltage and input power are 580 k V and 30.0GW,respectively,with the change of the outer radius of SWS,HPM is generated with a maximum output power of 7.1 GW,a frequency of 1.440 GHz,a power efficiency of23.7%.Under the same input electrical parameters,the 3 d B tunable frequency range is0.75?2.10 GHz and the 3 d B tunning bandwidth is 94.7%.With the increment of the input electrical parameters,when the applied voltage and input power are 815 k V and59.5 GW,respectively,HPM is generated with an maximum output power of 16.4 GW,a frequency of 1.440 GHz,a power efficiency of 27.6%3.Simulation studies of tunable mode converterA high-efficiency tunable mode converter(HETMC)with coaxial flashboard is proposed.Under the frequency band of 1.63?2.12 GHz,the conversion efficiency of the HETMC is above 95%and the corresponding tunning bandwidth is 26.1%.A tunable turnstile mode converter(TTMC)with linearly polarized mode is presented,which owes advantages of simpler structure,more convenient tunning mechanism,wider tunning bandwidth and higher conversion efficiency,a TEM-TTMC with linearly polarized output TE₁₁ mode is researched.Under the frequency band of1.45?2.35 GHz,the conversion efficiency of the TTMC is above 99%and the corresponding tunning bandwidth is 47.4%.4.Experiment studies of tunable MILO systemLow-power experimental investigation of the TTMC show that it can convert the coaxial waveguide TEM mode into circular waveguide linearly polarized TE₁₁ mode with efficiency more than 99%under the frequency range 1.55?2.35 GHz.The measured patterns of the TTMC's input power are in good agreement with the simulated patterns,which indicates that the mode in pure.High-power expermental investigation of the conventional tunable MILO system verifies the feasibility of the tunable scheme.When the applied voltage,the pulse width and the current are about 486 k V,90 ns and 51 k A,respectively,HPM is generated with a maximum output power of 3.7 GW and a power efficiency of 14.8%,the microwave pulse width is 29 ns.Under the same input electrical parameters,the 3 d B tunable frequency range is 1.552?2.168 GHz and the 3 d B tunning bandwidth is 33.1%.High-power expermental investigation of the ridged tunable MILO system verifies the feasibility of the tunable scheme.When the applied voltage,the pulse width and the current are about 510 k V,90 ns and 49 k A,respectively,HPM is generated with a maximum output power of 4.3 GW and a power efficiency of 16.8%,the microwave pulse width is 43 ns.Under the same input electrical parameters,the 3 d B tunable frequency range is 1.536?2.100 GHz and the 3 d B tunning bandwidth is 31.0%.