Comparative Studies Of Coaxial And Cylindrical Bragg Reflectors

With the higher request on output reflectivity of the resonance cavity,the problems of the ohmic wall loading and mode competition have been paid much attention.Aim at the study actuality,a new type of device----Coaxial Bragg reflector has been brought forward in this task.One of the advantages of the coaxial-cavity is increase the area of dispersing heat and improve the capability of dispersing heat;in addition,the coaxial structures can be successfully employed to achieve higher power levels with reduced the problem of mode competition.In this paper a comprehensive theory is first presented to analyze the multi-mode coupling in a coaxial Bragg reflector,including the derivation of the coupled equations,the coupling coefficient and the attenuation coefficient of the multi modes.A simulation code has been made by FORTRAN to compute both reflectivity equations of cylindrical-cavity and coaxial-cavity Bragg reflector.Comparison of performance between the coaxial and cylindrical Bragg reflectors,where the operating mode was TE₁₁mode at a frequency of 250 GHz,the results shows that the former has the advantages of better mode selectivity and larger dimensional size.For the coaxial Bragg reflector,through numerical studies illustrated attractive peculiarities with both the outer wall and the inner rod corrugated:the operating mode can get strong reflectivity and the spurious modes are well suppressed,even if the reflector with large dimensional size operates in higher-order mode at hundreds of Gigahertz.Especially indicate that the reflectivity of a coaxial Bragg reflector is optimized when the outer and inner conductors have the same corrugation period.