Abstract
By making use of coupled-wave theory, the transmission characteristics of a defected coaxial Bragg structure which operates in the vicinity of 100 GHz are investigated. Results reveal that the overmoded operation of the example structure excites serious interaction among the operating mode and its neighboring modes, which spoils the passband structure and causes hybrid-mode transmission. However, single-mode output can be ensured by applying Hamming-window-function distribution to the ripple amplitude of the example structure, and one or more desired narrow passbands can be generated and controlled by adjusting the localized ripple defect or/and the initial phase difference between the outer-wall and the inner-rod ripples. These peculiarities provide potential applications of defected coaxial Bragg waveguides in constructing high-Q open resonators and narrow passband filters in the sub-terahertz and terahertz frequency ranges.