Coupled Circular Cavities for Transit-Time Microwave Tubes

We examine both analytically and numerically by using a 2-D electromagnetic solver the frequency tuning characteristics and electric-field patterns in a two-celled system consisting of cylindrical cavities coupled by a circular iris. It is shown that the presence of the iris introduces unique features not found in hollow circular cavities, namely, the occurrence of flat portions on the frequency tuning curves for varying iris radius and also a $Q$ factor 10% higher than that of the otherwise smooth cavity.