Research On An X-band Cerenkov Type High-power Microwave Oscillator Without Guiding Magnetic Field

The development of High-Power Microwave(HPM) technology has stimulated intense interests in the compactness, practicability of the HPM generators. With optimized structure, HPM generators without guiding magnetic field can achieve miniaturization at the same time of getting high output power and relatively high efficiency. However, current researches on the HPM generators without guiding magnetic field, currently, are concentrated on the relatively low operation waveband(L-, S-, and C-band). Accordingly, this thesis proposed an X-band Cerenkov type HPM oscillator without guiding magnetic field, which has been investigated through physical analysis and Particle-in-Cell(PIC) simulation. The main contents of this thesis are listed as follows.Firstly, based on the analysis of Cerenkov type oscillators without guiding magnetic field, a structure of the mentioned oscillator on X-band is proposed. Principles of the oscillator are described and related problems are analyzed physically. Transportation characteristics of the relativistic electron beam(REB) without the guiding of external magnetic field are investigated, and the results show that the electrons in the outer and inner space have different transportation characteristics in the radial direction. A confining cathode is designed to confine the spread of the REB in the radial direction. Analytical method is used to investigate the dispersion characteristics of the slow-wave structures(SWSs), and cold cavity analysis is used to study the electric field distribution of the SWSs. The effect of the tapered collector in collecting electrons is analyzed. The tapered collector can also be utilized to convert the TM01 mode microwave in the SWS into pure TEM mode in the output waveguide.Secondly, the proposed device is simulated by a 2.5-dimensional PIC code. The influence of structure parameters and operation parameters on the performance of the device is investigated, including the number of the periods and the ripple depth of the SWS, the radius and length of the tapered collector, the confining structure of the cathode, the diode voltage and the beam current. A focusing structure of the cathode is introduced to the basic geometry, with its effect of focusing the electrons analyzed. Through a series of optimization, the simulation results indicate that a TEM mode microwave is generated by the optimized oscillator with output power of 1.9GW and frequency of 9.1GHz, when the diode voltage and beam current are 620 k V and 9 k A, respectively. The corresponding power conversion efficiency is approximately 34%.The detailed beam-wave interaction process is then analyzed. On the basis of the analysis of the axial beam-wave interaction process, the mechanism of radial beam-wave interaction which occurs in the proposed device is investigated through physical analysis and PIC simulation.In the end, experimental design of the proposed device is carried out. With a high frequency simulation software, radiation components, including supporters, mode converter, and antenna, are investigated. The design and manufacture of this X-band Cerenkov type oscillator without guiding magnetic field are completed.