Research On Higher Order Transverse Magnetic Mode Of Microwave Cylindrical Coaxial Cavity And Its Out-coupling

The inter-related parameters of higher order transverse magnetic (HOTM) modes in coaxial cavity are calculated and analyzed in this dissertation. Not only is the HOTM mode chart plotted, but the variation of characteristic impedance with the cavity size, frequency and mode orders is analyzed as well.It is found that the lower orders of modes, the wider of the modes separation in cylindrical cavity. Higher order modes in higher frequency correspond to small cylindrical cavity which results in lower power whereas to considerable mode separations with larger coaxial cavity which conduce to higher power. So the cylindrical cavity can be employed merely in low frequency and lower order mode. For some given coaxial cavity configuration of JM_n10 modes, there exists maximum of characteristic impedance with variation of cavity inner radius. The results calculated are in good agreement accurately with that of simulation and can serve as a database from which the optimum parameters of design can be gotten instantly instead of time-consuming simulation by trial and error.The unloaded Q of HOTM modes in cylindrical and coaxial cavity are calculated and verified with software HFSS. The results are referential to design of accelerators cavity. Also some characteristic parameters in coaxial cavity with drift tubes are simulated and analyzed.Research on coupling of TM_n10 modes in coaxial cavity with TE₁₀ mode in rectangular waveguide is carried out based on the methods of one-port equivalent circuit and of phase echo. External Q is simulated for different 3-dimensions of the slot as well as single gap impedance of output cavity on special optimum configuration. To obtain symmetrical characteristic impedance of TM₃₁₀ in output coaxial cavity, the position of shot rod is adjusted, concave pits on the wall of cavity whose dimension is like the coupling hole is designed. Also the configuration of holes on coaxial cavity inner wall is designed and simulated to couple with radial transmission line then coaxial line.