Abstract: By making use of an electromagnetic simulation tool Ansoft HFSS, transmission characteristics of an example defected coaxial Bragg waveguide operating at Ka band (centred in 37.5 GHz) have been numerically studied. Results show that, if one conductor or both of outer and inner conductors are corrugated with periodical ripples, one or more passbands can be effectively generated by introducing a phase-shift defect to each corrugated surface; for the latter case, if the initial phase difference between the outer-wall ripple and inner-rod ripple is set to and the defects are both in the middle of the waveguide, a passband with extremely narrow bandwidth and wide stop-band rejection frequency range can be achieved; a slight misalignment of the defects between the outer-wall and inner-rod defects can be used to perform a fine adjustment on the character of the passband; however, if these defects are separated with a larger gap, several passbands can be generated, which makes the structure be acted as a multichannel filter. These numerical results are expected to provide engineering references for different applications of defected coaxial Bragg waveguides.