Abstract
Design and analysis of a 35 GHz metal photonic band gap (PBG) resonant cavity operating in the TE041-like mode has been presented. The dispersion characteristics of a 2D metal PBG structure comprising of triangular array of rods has been obtained using FDTD method. Global band gap regions have been obtained to be used for the PBG cavity design. A mode map has been also generated to examine the occurrence of the possible modes in the PBG cavity. Electromagnetic simulation of the designed PBG cavity has been performed to study the operating modes and quality factors. Role of the number of metal rods layers around the defect in PBG structure has also been illustrated for confining the desired mode and deciding the diffractive quality factor. PBG cavity results have been compared with the analogous cylindrical cavity for the designed mode along with the possible nearby modes to examine the mode competition. It has been found that the mode competition has been successfully reduced in designed PBG cavity and nearly a single mode operation is achieved. It is hoped that present study would be useful for the application of the metal PBG structures in the Gyrotron devices to alleviate the mode competition problem while operating in the higher order modes.
Highlights
Gyrotrons have emerged as the potential device for the generation of high power millimeter and sub-millimeter waves with good efficiency among various devices of its class
The objective of this paper is to demonstrate the mode selective operation of the photonic band gap (PBG) cavities to be used in the gyrotron devices as its RF interaction structure while operating at the higher order modes
The designed PBG cavity is simulated for its electromagnetic behavior using a commercial simulation code “CST Microwave Studio”
Summary
Gyrotrons have emerged as the potential device for the generation of high power millimeter and sub-millimeter waves with good efficiency among various devices of its class. High frequency operations of gyrotrons have made it possible to use them for newer applications but still many challenges remain in terms of achieving stable single mode operation of the overmoded cavities. At such higher frequency operation, significant reduction in transverse dimension of the RF interaction cavities lead to increase in heat load on the cavity walls, fabrication difficulties as well as increased problem of the beam interception [4].
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