High-power Microwave Circular Waveguide Mode Converter

As the continuing demands of higher power, higher energy, higher frequency microwave sources in military and scientific research, under this background the High Power Microwave(HPM) technology is a new and frontier science which rose in the 1970s. This technology has developed rapidly and it is receiving widespread attention. Now it may be applied in many areas such as military and scientific experiment, industrial processing, new material preparing, medical science, biology, and so on.A certain HPM system generally include input coupler resonators system in HPM sources, HPM transmitting system, the output coupling system, waveguide mode converters, the transmitting and receiving antennas. The designing behavior of each subsystem usually plays an utmost important part in the whole HPM system. The HPM mode transformer plays an extremely important part in the HPM transmitting and receiving process. It can make the energy of HPM source to transmit and radiate in a requisite mothods. Therefore, it has very important value to study and apply. Supported by the gyrotron scientific research project, the mode converters of several kinds of HPM sources especially the gyrotron are studide in this paper with theoretical analysis and numerical simulation in depth. The mode converter with design and manufacture apply in the experiment of our research institute successfully. The main works of the paper are listed as following:First, analyse the development and application of the mode converter in HPM transmission system and the transform process of several different converte sequence from the HPM source output to transmitting antenna.Second, the issue of mode coupling in the radius changed and axis bent overmode circular waveguide is studied on the basis of coupled wave theory. A strict derivation is given for the relative power and converte efficiency formulate in curvature circular waveguide TM₀₁-TE₁₁ mode converter.Third, present a method called Runge-Kutta to solve the coupled wave equation mumerically. Obtain the optimization geometrical structure parameter of the mode converter under different frequency and bandwidth condition. Adopt the different geometrical structure and phase rematch technology to design the efficient, wideband and tight circular waveguide mode converter. The mutual relationship about the radius of the waveguide, curvature of bent circular waveguide, frequency and the bandwidth are also obtained.Fourth, simulate the structure of the mode converter by HFSS and CST Microwave studio,the efficiency, bandwidth and the S parameter results are in excellent agreement with the numerical optimization programme. The mode field drawings also displayed by the software simulation...