Bandgap Control Of Two-Dimensional Coaxial Bragg Structures With Helically Corrugated Conductors

The untunable bandgap is a difficult problem for Bragg structures constructed from corrugated metallic waveguides, and becomes a major barrier for applications. Based on the coupled-mode theory, this paper presents the principle as well as a corresponding theoretical model of bandgap control of two-dimensional coaxial Bragg structures under the condition of a fixed ripple shape. It is shown that such control can be achieved by varying the angular deviation between the outer and inner corrugations, which can be done by rotating one of the conductors relative to the other. The effects of the proposed method on transmission bandgap control of two example structures were investigated by theoretical analysis and electromagnetic simulation. The results confirmed the validity of the proposal, and showed that such a control method can be used to manipulate the number and location of the working bands under multiple bandgap operation. These peculiarities provide potential applications of two-dimensional coaxial Bragg structures in constructing tunable passive and active high-power microwave devices.