Abstract
We present studies of a higher-order-mode coupling device, which employs a circular waveguide to coaxial transition (CWCT). The waveguide is double-ridged. A properly shaped back cavity at the far end allows broadband coupling to a coaxial window. Configurations of CWCTs with either symmetric or asymmetric ridge depth are optimized with the HFSS code. HFSS calculations have also been performed to examine CWCT damping effects on a DORIS box cavity. The anti-symmetric modes are shown to be much more effectively damped by the asymmetric CWCT, however, relative merits of symmetric and asymmetric CWCTs depend on other factors such as the cavity configuration. We also make optimizations of CWCT structure and discuss the fundamental mode damping effect of our newly designed symmetric coupler. A simulation study of the vacuum window for 7/8” coaxial is also included as an appendix.